Atari ST and hard disks - Revision history

>Wongck: /* A little history for better understanding: */

2011-10-15T10:21:59Z

A little history for better understanding:

← Older revision		Revision as of 06:21, 15 October 2011
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	===A little history for better understanding:===		===A little history for better understanding:===

	When the Atari ST was launched, in 1985 hard disks were not much used - they were too expensive, exotic pieces of hardware. Standards were not established, and there was no IDE (ATA), later winner in mass storage system for masses :-) Atari added some support for the (future) connection of hard disks in the form of the [[ACSI]] port. It was typical for that time: proprietary, and thus not compatible with any other. But it was not so bad a , considering the lack of standards. And ACSI port is actually some kind of simplified [[SCSI]] port. After it, some hard disks appeared on market. More success than Atari had independent manufacturers. Typical hard disk kit for Atari ST machines was: ACSI-SCSI adapter and SCSI disk + power supply + driver, partioning software. In the meantime IDE hard disks appeared on the market. They were designed to be cheap, simple interfaceable. Atari made support for IDE disks somewhere in 1991-92. Code for boot from such interface/disk was added to [[TOS]] 2.06, and the latest machines such as the ST-Book and Falcon had built-in IDE interface.		When the Atari ST was launched, in 1985 hard disks were not much used - they were too expensive, exotic pieces of hardware. Standards were not established, and there was no IDE (ATA), later winner in mass storage system for masses :-) Atari added some support for the (future) connection of hard disks in the form of the [[ACSI]] port. It was typical for that time: proprietary, and thus not compatible with any other. But it was not so bad a , considering the lack of standards. And ACSI port is actually some kind of simplified [[ACSI, SCSI and IDE#SCSI\| SCSI]] port. After it, some hard disks appeared on market. More success than Atari had independent manufacturers. Typical hard disk kit for Atari ST machines was: ACSI-SCSI adapter and SCSI disk + power supply + driver, partioning software. In the meantime IDE hard disks appeared on the market. They were designed to be cheap, simple interfaceable. Atari made support for IDE disks somewhere in 1991-92. Code for boot from such interface/disk was added to [[TOS]] 2.06, and the latest machines such as the ST-Book and Falcon had built-in IDE interface.
	However, at the time some people did not realise what was really happening: I read in an article in a German Atari magazine that it was not wise to produce an IDE interface, because SCSI was just little more expensive, and IDE has no perspective. Now we know that they were wrong. The biggest problem with an IDE interface is that it can not be simple connected to machine - you need to open the case and solder a lot of lines. In case of [[Mega ST]]s it was a little simpler, but still some soldering and mounting connector was required.		However, at the time some people did not realise what was really happening: I read in an article in a German Atari magazine that it was not wise to produce an IDE interface, because SCSI was just little more expensive, and IDE has no perspective. Now we know that they were wrong. The biggest problem with an IDE interface is that it can not be simple connected to machine - you need to open the case and solder a lot of lines. In case of [[Mega ST]]s it was a little simpler, but still some soldering and mounting connector was required.
	Now we have the absurd situation that some Atari users have a ACSI-SCSI-IDE chain of interfaces. The main problem here is that Atari went bankrupt after 1992, and that there is no expansion port/bus on ST machines.		Now we have the absurd situation that some Atari users have a ACSI-SCSI-IDE chain of interfaces. The main problem here is that Atari went bankrupt after 1992, and that there is no expansion port/bus on ST machines.


	===How it works?===		===How it works?===

>Wongck at 15:37, 10 October 2011

2011-10-10T15:37:24Z

← Older revision		Revision as of 11:37, 10 October 2011
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	[http://joo.kie.sk/ultrasatan/ UltraSatan] and [http://joo.kie.sk/satandisk/ SatanDisk] fill the need that was not met as alluded to above in 2007. These devices perform ASCI -> SD/MMC card translation and replace the ordinary hard disks.		[http://joo.kie.sk/ultrasatan/ UltraSatan] and [http://joo.kie.sk/satandisk/ SatanDisk] fill the need that was not met as alluded to above in 2007. These devices perform ASCI -> SD/MMC card translation and replace the ordinary hard disks.
	Certainly that some memory card is the best solution in 2010. Prices are now low - 4GB quality SD card (Kingston) costs about 10-12 Euros. Data exchange with some PC is piece of cake. Of course when using TOS/DOS compatible partitioning.		Certainly that some memory card is the best solution in 2010. Prices are now low - 4GB quality SD card (Kingston) costs about 10-12 Euros. Data exchange with some PC is piece of cake. Of course when using TOS/DOS compatible partitioning.
			<br />
			<br />
			<br />
			[[Category:Storage]]

>Wongck: /* Limitations */

2011-08-31T14:48:54Z

Limitations

← Older revision		Revision as of 10:48, 31 August 2011
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	We should not blame Atari too much for those limits, in comparison, for the PC the situation was even worse - max half GB total disk size accessible with CHS addressing by IDE/MFM disks. Not to mention mess in partition tables.		We should not blame Atari too much for those limits, in comparison, for the PC the situation was even worse - max half GB total disk size accessible with CHS addressing by IDE/MFM disks. Not to mention mess in partition tables.
	IDE (ATA) went through numerous expansions. The most important is LBA addressing, which allows hard disks sizes of up to 128GB capacity. Latest expansion is 48-bit addressing. Not really interesting for old machines, but latest driver versions support even it.		IDE (ATA) went through numerous expansions. The most important is LBA addressing, which allows hard disks sizes of up to 128GB capacity. Latest expansion is 48-bit addressing. Not really interesting for old machines, but latest driver versions support even it.
	BigDOS partitions on PC have a limit of 2GB in size, and they are readable on an Atari with help of the free program BIGDOS + hard disk driver, at least AHDI 3.0 compat. More details here: http://~~ppera~~.~~07x~~.~~net~~/atari/ASThdFAQ.html .		BigDOS partitions on PC have a limit of 2GB in size, and they are readable on an Atari with help of the free program BIGDOS + hard disk driver, at least AHDI 3.0 compat. More details here: http://www.8bitchip.info/atari/ASThdFAQ.html.

	===Partitioning of hard disks===		===Partitioning of hard disks===

>Wongck at 14:46, 31 August 2011

2011-08-31T14:46:48Z

← Older revision		Revision as of 10:46, 31 August 2011
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	'''Atari ST and hard disks'''		'''Atari ST and hard disks'''

	Here we will focus mostly on [[ST]] and [[STE]] machines, but much of this remains the same with the Atari [[Falcon]] and [[TT]] machines too.		Here we will focus mostly on [[ST]] and [[STE]] machines, but much of this remains the same with the Atari [[Falcon 030]] and [[TT]] machines too.

>Wongck at 14:45, 31 August 2011

2011-08-31T14:45:32Z

← Older revision		Revision as of 10:45, 31 August 2011
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	== Atari ST and hard disks ==		'''Atari ST and hard disks'''

	Here we will focus mostly on [[ST]] and [[STE]] machines, but much of this remains the same with the Atari [[Falcon]] and [[TT]] machines too.		Here we will focus mostly on [[ST]] and [[STE]] machines, but much of this remains the same with the Atari [[Falcon]] and [[TT]] machines too.


	~~'''~~A little history for better understanding:~~'''~~		===A little history for better understanding:===

	When the Atari ST was launched, in 1985 hard disks were not much used - they were too expensive, exotic pieces of hardware. Standards were not established, and there was no IDE (ATA), later winner in mass storage system for masses :-) Atari added some support for the (future) connection of hard disks in the form of the [[ACSI]] port. It was typical for that time: proprietary, and thus not compatible with any other. But it was not so bad a , considering the lack of standards. And ACSI port is actually some kind of simplified [[SCSI]] port. After it, some hard disks appeared on market. More success than Atari had independent manufacturers. Typical hard disk kit for Atari ST machines was: ACSI-SCSI adapter and SCSI disk + power supply + driver, partioning software. In the meantime IDE hard disks appeared on the market. They were designed to be cheap, simple interfaceable. Atari made support for IDE disks somewhere in 1991-92. Code for boot from such interface/disk was added to [[TOS]] 2.06, and the latest machines such as the ST-Book and Falcon had built-in IDE interface.		When the Atari ST was launched, in 1985 hard disks were not much used - they were too expensive, exotic pieces of hardware. Standards were not established, and there was no IDE (ATA), later winner in mass storage system for masses :-) Atari added some support for the (future) connection of hard disks in the form of the [[ACSI]] port. It was typical for that time: proprietary, and thus not compatible with any other. But it was not so bad a , considering the lack of standards. And ACSI port is actually some kind of simplified [[SCSI]] port. After it, some hard disks appeared on market. More success than Atari had independent manufacturers. Typical hard disk kit for Atari ST machines was: ACSI-SCSI adapter and SCSI disk + power supply + driver, partioning software. In the meantime IDE hard disks appeared on the market. They were designed to be cheap, simple interfaceable. Atari made support for IDE disks somewhere in 1991-92. Code for boot from such interface/disk was added to [[TOS]] 2.06, and the latest machines such as the ST-Book and Falcon had built-in IDE interface.
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	~~'''~~How it works?~~'''~~		===How it works?===

	Unlike modern PCs, there is very little support for hard disks in TOS. Actually, in TOS there is only a small amount of code for loading the master boot record from hard disks. The rest is done by the driver and it's loader. TOS has support for FAT16 filesystem - MS DOS compatible. Later TOS versions added some support for bigger FAT16 partitions in the form of 'Big sectors'. This also required compatible hard disk drivers.		Unlike modern PCs, there is very little support for hard disks in TOS. Actually, in TOS there is only a small amount of code for loading the master boot record from hard disks. The rest is done by the driver and it's loader. TOS has support for FAT16 filesystem - MS DOS compatible. Later TOS versions added some support for bigger FAT16 partitions in the form of 'Big sectors'. This also required compatible hard disk drivers.


	~~'''~~Limitations~~:'''~~		===Limitations===

	TOS 1.0 was limited to partition sizes with a max of 16MB due to a bug (without big sectors). FAT16 partition has a max size of 32MB. FAT16 with big sectors, called BGM may be up to 1GB, depending on TOS version.		TOS 1.0 was limited to partition sizes with a max of 16MB due to a bug (without big sectors). FAT16 partition has a max size of 32MB. FAT16 with big sectors, called BGM may be up to 1GB, depending on TOS version.
	ACSI in it's initial form has a limit of 1GB for total size of an attached hard disk, because of the addressing system. It was expanded ~~later in XHDI~~.		ACSI in it's initial form has a limit of 1GB for total size of an attached hard disk, because of the addressing system. It was expanded by ICD, supporting SCSI commands with 32-bit addressing. But it works only with best ICD adapters and new UltraSatan ACSI-SD card adapter (2009).
	~~But we~~ should not blame Atari too much for those limits, in comparison, for the PC the situation was even worse - max half GB total disk size accessible with CHS addressing by IDE/MFM disks. Not to mention mess in partition tables.		We should not blame Atari too much for those limits, in comparison, for the PC the situation was even worse - max half GB total disk size accessible with CHS addressing by IDE/MFM disks. Not to mention mess in partition tables.
	IDE (ATA) went through numerous expansions. The most important is LBA addressing, ~~whic~~ allows hard disks sizes of up to 128GB capacity.		IDE (ATA) went through numerous expansions. The most important is LBA addressing, which allows hard disks sizes of up to 128GB capacity. Latest expansion is 48-bit addressing. Not really interesting for old machines, but latest driver versions support even it.
	BigDOS partitions on PC have a limit of 2GB in size, and they are readable on an Atari with help of the free program BIGDOS + hard disk driver (at least AHDI 3.0 compat.)		BigDOS partitions on PC have a limit of 2GB in size, and they are readable on an Atari with help of the free program BIGDOS + hard disk driver, at least AHDI 3.0 compat. More details here: http://ppera.07x.net/atari/ASThdFAQ.html .

			===Partitioning of hard disks===
	~~'''~~Partitioning of hard disks~~:'''~~

	In the very first sector of every hard disk is the partition table. Atari uses the so called GEMDOS partition table. It is defined in AHDI. However, we are not forced to use that system at all - because there is nothing in TOS related to it. All this is done by the hard disk driver. Usage of MS DOS partition system offers another possibility - it uses the same FAT16 partitions as GEMDOS. And we have the added benefit that such a disk will be readable on a PC without any special software.		In the very first sector of every hard disk is the partition table. Atari uses the so called GEMDOS partition table. It is defined in AHDI. However, we are not forced to use that system at all - because there is nothing in TOS related to it. All this is done by the hard disk driver. Usage of MS DOS partition system offers another possibility - it uses the same FAT16 partitions as GEMDOS. And we have the added benefit that such a disk will be readable on a PC without any special software.


	~~'''~~Speed~~:'''~~		===Speed===

	Speed depends on a combination of the attached drive, the interface, the DMA chip in ST (ACSI port), the ST's CPU speed and driver, with the transfer speed constrained by the slowest part of the chain.		Speed depends on a combination of the attached drive, the interface, the DMA chip in ST (ACSI port), the ST's CPU speed and driver, with the transfer speed constrained by the slowest part of the chain.
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	~~'''Where we are today (~~2007) ?~~'''~~		===What was the situation in 2007?===

	Still some people use Atari ST machines. Things have changed a lot from the 1980s till now, we now have cheap Flash mass storage media, with low power consumption, and fast speeds. SCSI is developed too, but it is not for the mass-market. Nobody manufactures ACSI-SCSI adapters. The ideal would be an ACSI-IDE or a ACSI-some Flash card interface, but from some reasons they are not available, although there are some projects under development/manufacturing. IDE has advanced so that CD ROM/DVDs can be attached too.		Still some people use Atari ST machines. Things have changed a lot from the 1980s till now, we now have cheap Flash mass storage media, with low power consumption, and fast speeds. SCSI is developed too, but it is not for the mass-market. Nobody manufactures ACSI-SCSI adapters. The ideal would be an ACSI-IDE or a ACSI-some Flash card interface, but from some reasons they are not available, although there are some projects under development/manufacturing. IDE has advanced so that CD ROM/DVDs can be attached too.
Line 46:		Line 45:
	The problem is when someone wants to buy an adapter and mass storage media: What should they buy today?		The problem is when someone wants to buy an adapter and mass storage media: What should they buy today?
	Currently they may have go to E-bay and look for a second-hand combination. Of course, the prices are not too good, considering that a new Flash card of 4GB costs under 50 Euros, and will be become gradually cheaper.		Currently they may have go to E-bay and look for a second-hand combination. Of course, the prices are not too good, considering that a new Flash card of 4GB costs under 50 Euros, and will be become gradually cheaper.
	~~Or waiting...~~

	~~P. Putnik , March 2007.~~



	~~Jump to~~ [[~~IDE_%26_SCSI_Drivers~~]~~] page~~		===Where we are today (2009) ?===
			[http://joo.kie.sk/ultrasatan/ UltraSatan] and [http://joo.kie.sk/satandisk/ SatanDisk] fill the need that was not met as alluded to above in 2007. These devices perform ASCI -> SD/MMC card translation and replace the ordinary hard disks.
			Certainly that some memory card is the best solution in 2010. Prices are now low - 4GB quality SD card (Kingston) costs about 10-12 Euros. Data exchange with some PC is piece of cake. Of course when using TOS/DOS compatible partitioning.

>Wongck: /* Atari ST and hard disks */

2011-07-08T08:02:05Z

Atari ST and hard disks

← Older revision		Revision as of 04:02, 8 July 2011
Line 49:		Line 49:

	P. Putnik , March 2007.		P. Putnik , March 2007.



			Jump to [[IDE_%26_SCSI_Drivers]] page

>Zenichiro: Fixed formatting, minor edits for better English, slightly wikified

2007-09-26T22:28:03Z

Fixed formatting, minor edits for better English, slightly wikified

← Older revision		Revision as of 18:28, 26 September 2007
Line 1:		Line 1:
	Atari ST and hard disks		== Atari ST and hard disks ==

	Here we will focus mostly on ST and STE machines, but ~~many~~ of ~~written stays for~~ Atari Falcon and		Here we will focus mostly on [[ST]] and [[STE]] machines, but much of this remains the same with the Atari [[Falcon]] and [[TT]] machines too.

	~~TT machines too.~~

	~~Little~~ history for better understanding:		'''A little history for better understanding:'''

	When Atari ST was launched, in 1985 hard disks were not much used - they were too expensive, exotic pieces of hardware. Standards were not established, and there was no IDE (ATA), later winner in mass storage system for masses :-) Atari ~~did~~ some support for ~~attaching~~ (~~in that time yet~~ future) hard disks in form of ACSI port. It was typical for that time: ~~usage of own system~~, not compatible with any other. But it was not so bad ~~move~~, considering lack of standards. And ACSI port is actually some kind of simplified SCSI port. After it, some hard disks appeared on market. More success than Atari had independent manufacturers. Typical hard disk kit for Atari ST machines was: ACSI-SCSI adapter and SCSI disk + power supply + driver, ~~partitioner~~ software. In meantime IDE hard disks appeared on market. They were designed to be cheap, simple interfaceable. Atari made support for IDE disks somewhere in 1991-92. Code for boot from such interface/disk is added to TOS 2.06, and latest machines as ST-Book and Falcon had built-in IDE interface.		When the Atari ST was launched, in 1985 hard disks were not much used - they were too expensive, exotic pieces of hardware. Standards were not established, and there was no IDE (ATA), later winner in mass storage system for masses :-) Atari added some support for the (future) connection of hard disks in the form of the [[ACSI]] port. It was typical for that time: proprietary, and thus not compatible with any other. But it was not so bad a , considering the lack of standards. And ACSI port is actually some kind of simplified [[SCSI]] port. After it, some hard disks appeared on market. More success than Atari had independent manufacturers. Typical hard disk kit for Atari ST machines was: ACSI-SCSI adapter and SCSI disk + power supply + driver, partioning software. In the meantime IDE hard disks appeared on the market. They were designed to be cheap, simple interfaceable. Atari made support for IDE disks somewhere in 1991-92. Code for boot from such interface/disk was added to [[TOS]] 2.06, and the latest machines such as the ST-Book and Falcon had built-in IDE interface.
	However, some people did not ~~realised in that time~~ what really happening: I read in ~~some~~ article in German Atari magazine that it ~~is no~~ wise to ~~make~~ IDE interface, because SCSI is just little more expensive, and IDE has no perspective. Now we know that they were wrong. ~~Biggest~~ problem with IDE interface is that it can not be simple connected to machine - you need to open case and solder lot of lines. In case of Mega ~~STs~~ it was little simpler, but still some soldering and mounting connector was required.		However, at the time some people did not realise what was really happening: I read in an article in a German Atari magazine that it was not wise to produce an IDE interface, because SCSI was just little more expensive, and IDE has no perspective. Now we know that they were wrong. The biggest problem with an IDE interface is that it can not be simple connected to machine - you need to open the case and solder a lot of lines. In case of [[Mega ST]]s it was a little simpler, but still some soldering and mounting connector was required.
	Now we have absurd situation that some Atari users have ACSI-SCSI-IDE chain of interfaces. ~~Main~~ problem here is that Atari ~~bankrupted~~ after 1992, and that there is no expansion port/bus on ST machines.		Now we have the absurd situation that some Atari users have a ACSI-SCSI-IDE chain of interfaces. The main problem here is that Atari went bankrupt after 1992, and that there is no expansion port/bus on ST machines.

	~~How it works?~~

	~~Unlike by modern PCs, there is only very little support for hard disks in TOS. Actually, in TOS is only short code for loading master boot record from hard disks. All further is done by driver and~~ it'~~s loader. TOS has support for FAT16 filesystem - MS DOS compatible. Later TOS versions added some support for bigger FAT16 partitions in form of~~ '~~Big sectors~~'~~. All that required (compatible) hard disk drivers.~~		'''How it works?'''

			Unlike modern PCs, there is very little support for hard disks in TOS. Actually, in TOS there is only a small amount of code for loading the master boot record from hard disks. The rest is done by the driver and it's loader. TOS has support for FAT16 filesystem - MS DOS compatible. Later TOS versions added some support for bigger FAT16 partitions in the form of 'Big sectors'. This also required compatible hard disk drivers.

	~~Limitations:~~

	TOS 1.0 was limited to partition sizes of max 16MB due to bug (without big sectors). FAT16 partition has max size of 32MB. FAT16 with big sectors, called BGM may be up to 1GB, depending on TOS version.		'''Limitations:'''
	~~ACSI in it~~'~~s initial form has limit of 1GB for total size of attached hard disk, because of addressing system. It is expanded later in XHDI.~~
	But we should not blame Atari much for those limits. By PC, situation was even worse - max half GB total disk size accessible with CHS addressing by IDE/MFM disks. Not to mention mess in partition tables.
	~~IDE (ATA) went through numerous expansions. Most important is LBA addressing, what accessess hard disks up to 128GB capacity.~~
	~~BigDOS partitions on PC have limit of 2GB in size, and they are readable on Atari with help of free program BIGDOS + hard disk driver (at least AHDI 3.0 compat.)~~

			TOS 1.0 was limited to partition sizes with a max of 16MB due to a bug (without big sectors). FAT16 partition has a max size of 32MB. FAT16 with big sectors, called BGM may be up to 1GB, depending on TOS version.
			ACSI in it's initial form has a limit of 1GB for total size of an attached hard disk, because of the addressing system. It was expanded later in XHDI.
			But we should not blame Atari too much for those limits, in comparison, for the PC the situation was even worse - max half GB total disk size accessible with CHS addressing by IDE/MFM disks. Not to mention mess in partition tables.
			IDE (ATA) went through numerous expansions. The most important is LBA addressing, whic allows hard disks sizes of up to 128GB capacity.
			BigDOS partitions on PC have a limit of 2GB in size, and they are readable on an Atari with help of the free program BIGDOS + hard disk driver (at least AHDI 3.0 compat.)

	~~Partitioning of hard disks:~~

	~~In very first sector~~ of ~~every~~ hard disk is partition table. Atari uses so called GEMDOS partition table. It is defined in AHDI. However, we are not forced to use that system at all - because there is nothing in TOS related to it. All is done by hard disk driver. Usage of MS DOS partition system offers as other possibility - it uses same FAT16 partitions as GEMDOS. And we have benefit that such disk will be readable on PC without any special software.		'''Partitioning of hard disks:'''

			In the very first sector of every hard disk is the partition table. Atari uses the so called GEMDOS partition table. It is defined in AHDI. However, we are not forced to use that system at all - because there is nothing in TOS related to it. All this is done by the hard disk driver. Usage of MS DOS partition system offers another possibility - it uses the same FAT16 partitions as GEMDOS. And we have the added benefit that such a disk will be readable on a PC without any special software.

	~~Speed:~~

	Speed ~~depends from attached drive, interface, DMA chip in ST (ACSI port), ST~~'~~s CPU speed and driver. And will be not better than slowest part of chain.~~		'''Speed:'''
	In case of ACSI it is not exactly clear: some sources say that DMA chip can max 1MB/sec, others talk about max 1.5MB/sec (this are max. burst speeds, and we may just go close to them). It is even possible that earlier machine versions have lower max. speed and later higher. In any case we may say for now that ACSI can 1-1.4MB/sec maximum. In reality it means some 10-20% less by work with large files, and less speed with short files.
	IDE speed: it depends not from interface (which is just a I/O port). In case of 8MHz ST it can go up to 1.6MB/sec, and with blitter (STe, Mega ST) up to 1.8MB/sec. By Falcon it can be aprox. twice faster.
	But in case of MS DOS disks and CD ROM/DVDs IDE will be very slow. Reason is byte order, what is reversed by such disks. Swapping Low/High byte is pretty slow with MC68000, so we can expect speeds in range of 250-400KB/sec max. Some interfaces perform that byte-swap in hardware, so can work at max. speed as above (IDE speed). But such interfaces are not AHDI compatible.

			Speed depends on a combination of the attached drive, the interface, the DMA chip in ST (ACSI port), the ST's CPU speed and driver, with the transfer speed constrained by the slowest part of the chain.
			In the case of ACSI it is not exactly clear: some sources say that DMA chip can reach a max of 1MB/sec, others talk about a max of 1.5MB/sec (these are max. burst speeds, and we may just go close to them). It is even possible that earlier machine versions have a lower max. speed and later higher. In any case we may say for now that ACSI has a 1-1.4MB/sec maximum. In reality this means some 10-20% less when working with large files, and less speed again with short files.
			IDE speed: it depends not on the interface (which is just a I/O port). In the case of an 8MHz ST it can go up to 1.6MB/sec, and with a [[blitter]] chip fitted (STe, Mega ST) up to 1.8MB/sec. For a Falcon it can be aprox. twice as fast.
			But in the case of MS DOS disks and CD ROM/DVDs IDE will be very slow. The reason is byte order, what is reversed by such disks. Swapping Low/High byte is pretty slow with MC68000, so we can expect speeds in the range of 250-400KB/sec max. Some interfaces perform that byte-swap in hardware, so can work at max. speed as above (IDE speed), but such interfaces are not AHDI compatible.

	~~Where we are today (2007) ?~~

	Still some people uses Atari ST machines. Things changed a lot until 80-es of last century. We have now cheap Flash mass storage medias, with low power consumption, fast work. SCSI is developed too, but it is not for mass-market. Nobody manufactures ACSI-SCSI adapters. Ideal would be ACSI-IDE or ACSI-some Flash card interface. But from some reasons they are ~~not available, although there are some projects under development/manufacturing. IDE has advance that CD ROM/DVDs can be attached too.~~		'''Where we are today (2007) ?'''
	~~Problem is that ACSI and IDE~~ (~~ATA~~) are not compatible. For instance IDE has 16-bit data bus, while ACSI 8 . Even bigger problem is control: ACSI first gives command code, then parameters, while IDE does it in opposite order. So, designing ACSI-IDE IF is not so simple.

	There is still a lot of working, good quality ACSI-SCSI adapters used with Atari machines, and they are best supported by software. IDE is not so ~~good~~ supported, and most of drivers is obsolete.		Still some people use Atari ST machines. Things have changed a lot from the 1980s till now, we now have cheap Flash mass storage media, with low power consumption, and fast speeds. SCSI is developed too, but it is not for the mass-market. Nobody manufactures ACSI-SCSI adapters. The ideal would be an ACSI-IDE or a ACSI-some Flash card interface, but from some reasons they are not available, although there are some projects under development/manufacturing. IDE has advanced so that CD ROM/DVDs can be attached too.
	~~Problem~~ is when someone wants to buy adapter and mass storage media: ~~what to~~ buy today?		The problem is that ACSI and IDE (ATA) are not compatible. For instance IDE has 16-bit data bus, while ACSI has 8. An even bigger problem is control: ACSI first gives command code, then parameters, while IDE does it in the opposite order. So, designing an ACSI-IDE interface is not so simple.
	~~May~~ go to E-bay and look for ~~some~~ second-hand combination. ~~Prices~~ are not to good, considering that new Flash card of 4GB costs under 50 Euros, and will be gradually cheaper.
			There is still a lot of working, good quality ACSI-SCSI adapters used with Atari machines, and they are the best supported by the available software, where as IDE is not so well supported, and most of the drivers are obsolete.
			The problem is when someone wants to buy an adapter and mass storage media: What should they buy today?
			Currently they may have go to E-bay and look for a second-hand combination. Of course, the prices are not too good, considering that a new Flash card of 4GB costs under 50 Euros, and will be become gradually cheaper.
	Or waiting...		Or waiting...

	P. Putnik , March 2007.		P. Putnik , March 2007.

>Ppera at 17:39, 21 March 2007

2007-03-21T17:39:47Z

New page

Atari ST and hard disks

Here we will focus mostly on ST and STE machines, but many of written stays for Atari Falcon and

TT machines too.

Little history for better understanding:

When Atari ST was launched, in 1985 hard disks were not much used - they were too expensive, exotic pieces of hardware. Standards were not established, and there was no IDE (ATA), later winner in mass storage system for masses :-) Atari did some support for attaching (in that time yet future) hard disks in form of ACSI port. It was typical for that time: usage of own system, not compatible with any other. But it was not so bad move, considering lack of standards. And ACSI port is actually some kind of simplified SCSI port. After it, some hard disks appeared on market. More success than Atari had independent manufacturers. Typical hard disk kit for Atari ST machines was: ACSI-SCSI adapter and SCSI disk + power supply + driver, partitioner software. In meantime IDE hard disks appeared on market. They were designed to be cheap, simple interfaceable. Atari made support for IDE disks somewhere in 1991-92. Code for boot from such interface/disk is added to TOS 2.06, and latest machines as ST-Book and Falcon had built-in IDE interface.
However, some people did not realised in that time what really happening: I read in some article in German Atari magazine that it is no wise to make IDE interface, because SCSI is just little more expensive, and IDE has no perspective. Now we know that they were wrong. Biggest problem with IDE interface is that it can not be simple connected to machine - you need to open case and solder lot of lines. In case of Mega STs it was little simpler, but still some soldering and mounting connector was required.
Now we have absurd situation that some Atari users have ACSI-SCSI-IDE chain of interfaces. Main problem here is that Atari bankrupted after 1992, and that there is no expansion port/bus on ST machines.

How it works?

Unlike by modern PCs, there is only very little support for hard disks in TOS. Actually, in TOS is only short code for loading master boot record from hard disks. All further is done by driver and it's loader. TOS has support for FAT16 filesystem - MS DOS compatible. Later TOS versions added some support for bigger FAT16 partitions in form of 'Big sectors'. All that required (compatible) hard disk drivers.

Limitations:

TOS 1.0 was limited to partition sizes of max 16MB due to bug (without big sectors). FAT16 partition has max size of 32MB. FAT16 with big sectors, called BGM may be up to 1GB, depending on TOS version.
ACSI in it's initial form has limit of 1GB for total size of attached hard disk, because of addressing system. It is expanded later in XHDI.
But we should not blame Atari much for those limits. By PC, situation was even worse - max half GB total disk size accessible with CHS addressing by IDE/MFM disks. Not to mention mess in partition tables.
IDE (ATA) went through numerous expansions. Most important is LBA addressing, what accessess hard disks up to 128GB capacity.
BigDOS partitions on PC have limit of 2GB in size, and they are readable on Atari with help of free program BIGDOS + hard disk driver (at least AHDI 3.0 compat.)

Partitioning of hard disks:

In very first sector of every hard disk is partition table. Atari uses so called GEMDOS partition table. It is defined in AHDI. However, we are not forced to use that system at all - because there is nothing in TOS related to it. All is done by hard disk driver. Usage of MS DOS partition system offers as other possibility - it uses same FAT16 partitions as GEMDOS. And we have benefit that such disk will be readable on PC without any special software.

Speed:

Speed depends from attached drive, interface, DMA chip in ST (ACSI port), ST's CPU speed and driver. And will be not better than slowest part of chain.
In case of ACSI it is not exactly clear: some sources say that DMA chip can max 1MB/sec, others talk about max 1.5MB/sec (this are max. burst speeds, and we may just go close to them). It is even possible that earlier machine versions have lower max. speed and later higher. In any case we may say for now that ACSI can 1-1.4MB/sec maximum. In reality it means some 10-20% less by work with large files, and less speed with short files.
IDE speed: it depends not from interface (which is just a I/O port). In case of 8MHz ST it can go up to 1.6MB/sec, and with blitter (STe, Mega ST) up to 1.8MB/sec. By Falcon it can be aprox. twice faster.
But in case of MS DOS disks and CD ROM/DVDs IDE will be very slow. Reason is byte order, what is reversed by such disks. Swapping Low/High byte is pretty slow with MC68000, so we can expect speeds in range of 250-400KB/sec max. Some interfaces perform that byte-swap in hardware, so can work at max. speed as above (IDE speed). But such interfaces are not AHDI compatible.

Where we are today (2007) ?

Still some people uses Atari ST machines. Things changed a lot until 80-es of last century. We have now cheap Flash mass storage medias, with low power consumption, fast work. SCSI is developed too, but it is not for mass-market. Nobody manufactures ACSI-SCSI adapters. Ideal would be ACSI-IDE or ACSI-some Flash card interface. But from some reasons they are not available, although there are some projects under development/manufacturing. IDE has advance that CD ROM/DVDs can be attached too.
Problem is that ACSI and IDE (ATA) are not compatible. For instance IDE has 16-bit data bus, while ACSI 8 . Even bigger problem is control: ACSI first gives command code, then parameters, while IDE does it in opposite order. So, designing ACSI-IDE IF is not so simple.

There is still a lot of working, good quality ACSI-SCSI adapters used with Atari machines, and they are best supported by software. IDE is not so good supported, and most of drivers is obsolete.
Problem is when someone wants to buy adapter and mass storage media: what to buy today?
May go to E-bay and look for some second-hand combination. Prices are not to good, considering that new Flash card of 4GB costs under 50 Euros, and will be gradually cheaper.
Or waiting...

P. Putnik , March 2007.