TOS Partition Limit - 1.02 / 520STm - Legacy question

[Xebec]

I see per the ICD Drivers page that TOS 1.00-1.02 can support up to 16MB for a boot partition but then 256MB per subsequent partition..

 

However, "back in the day" when I ran a BBS on a 520ST with a SuperDrive 65MB hard drive (Seagate ST276N IIRC), I remember having to split into 4 x 16 MB partitions..  (Rather than 1 x 16 + 1 x 48 or whatever).  For BBS software I started with BBS Express ST! but later switched to FoReM because it handled reading/writing file transfer forums/folders across multiple drives effortlessly.  (No disk space management).

 

Were there older disk drivers / utilities back then that might have limited me to 16MB only even for subsequent partitions, or did I just not realize i could have partitioned it better?  (i.e. 1MB boot/BBS, and rest for file storage). 

 

Thanks!

[ParanoidLittleMan]

Actually, 16 MB limit for first (boot) partition is not TOS limit, for TOS all partitions are equal in that manner. The reason why some drivers have it is that main part of driver (usually some *.SYS file) is placed on partition C, and it can become fragmented - for instance when installing updated version. Code to read it is in master bootsector (MBR), and there space is limited. With smaller size partition it is simpler. Btw. there are ways to read and execute longer code from MBR, actually simple way, so that 16 MB limit is just limit of conception of driver.

Now, some small partition sizes limit for all of them is probably driver code limit. What might be because used C compiler limits, for instance.

I don't remember driver with such limits, but I really did not see much of them. Everything is possible in coding waters. Certainly, with drive sizes in those times it was not so bad to have smaller partitions.  I had 2.5 inch IBM drives of 160 MB, and all partitions were under 32 MB - with good reason - they were so TOS/DOS compatible.  For larger partitions than 32 MB special partitioning and driver is needed to have it.

There were limits with drives and adapters too - known 1 GB limit for ACSI (DMA) of Atari ST. IDE (AT bus) disk max capacity with CHS addressing - if remember correct it was 512 MB .

[ParanoidLittleMan]

Just received e-mail from one user of  TOS Extension Card by CodeHead Technologies - it is for TOS 2.06 in STs .

And what saw in original DOCs for it (PDF attached): "WARNING: Beginning with TOS 1.04, Atari computers allowed GEM hard drive partitions up to 32 megabytes in length; however TOS 1.00 and 1.02 are limited to 16 megabyte partitions."

Sadly, not so rare case of misinformation.

Edited January 25, 2021 by ParanoidLittleMan
clarifying

[Xebec]

13 hours ago, ParanoidLittleMan said:

Just received e-mail from one user of  TOS Extension Card by CodeHead Technologies - it is for TOS 2.06 in STs .

And what saw in original DOCs for it (PDF attached): "WARNING: Beginning with TOS 1.04, Atari computers allowed GEM hard drive partitions up to 32 megabytes in length; however TOS 1.00 and 1.02 are limited to 16 megabyte partitions."

Sadly, not so rare case of misinformation.

Thanks - would love to see the PDF if possible;  do you think ICD is incorrect here?

 

I guess I can pull my 520ST out of storage and do some tests with my UltraSatan... 

 

Thanks :) 

[ParanoidLittleMan]

Here is that PDF TOS_Extension_Card.zip

But that's not for some hard disk interface, I just looked thru it, and saw those false limits.

I did not see ICD driver DOCs, but that claim is certainly wrong. Why I know it ? Because my driver SW has no those special limits for first partition, and btw. any partition can be set as first (C:) during driver start. http://atari.8bitchip.info/pphdr.php

Plus, I know TOS well, and even did some improving of it's FAT16 code.

 

Possible that those claims about 16 and 32 MB limits are because lack of information - for larger partitions driver self need to reserve larger buffer space, so called BCB (buffer control blocks). Initially it is 2 KB, what is good for floppies, and hard disk partitions with logical sector size of 512 bytes. For larger ones larger logical sectors are needed, and that needs larger buffer space too. For 512 MB partitions 32 KB buffer space is needed (1.04 and above).

So, the correct statement would be: there are 'limits of TOS' - some are caused by TOS self, some are caused by lack, unavailability of DOCumentation, or just pure shallowness of those who published it.

To add, that 16 MB for partition was too little even in 1985. Just calculate how much is 1024/16 - 64 partitions would be needed to fill 1 GB drive - possible, but would need using some Chinese letters for later ones ?

[zzip]

6 hours ago, ParanoidLittleMan said:

Possible that those claims about 16 and 32 MB limits are because lack of information - for larger partitions driver self need to reserve larger buffer space, so called BCB (buffer control blocks). Initially it is 2 KB, what is good for floppies, and hard disk partitions with logical sector size of 512 bytes. For larger ones larger logical sectors are needed, and that needs larger buffer space too. For 512 MB partitions 32 KB buffer space is needed (1.04 and above).

So, the correct statement would be: there are 'limits of TOS' - some are caused by TOS self, some are caused by lack, unavailability of DOCumentation, or just pure shallowness of those who published it.

Well those were pre-internet days for most people.   It wasn't easy fact-check stuff as it is now.  People tended to believe the printed word.   If there's was an error in the documentation, then alot of Atari experts would quote the error as fact and it became common knowledge.

 

I know the reason I stuck with 32Gb partitions was that the Atari 'expert' I knew told me that was the limit for all partitions.   I didn't want to take chances with my data and create partitions larger than that.