DOS 3 Disk Image

[flashjazzcat]

There is a topic on DOS XE here, with complete info on FS structure and many internals, including why DOS XE, after all, turns over to be utter crap.

 

DOS 3 FS is limited to 256k. DOS 4 FS is limited to 384k. Both are wasteful: DOS 3 uses a 1k logical sector, and DOS 4 - a 1.5k logical sector (1 byte file takes 1.5k on the disk).

 

DOS XE FS is limited to 16 MB, but the implementation sucks to such extent that it makes no sense to use it (the DOS XE) with floppies bigger than 360k anyway.

 

Vaporware at its finest. Ok, DOS 3 was officially released, so it isn't real vaporware...

LOL! DOS-XE seemed to hold promise for a while... I can't wait to read about how badly it sucks.

 

Ach... I can't find the topic.

Edited July 22, 2010 by flashjazzcat

[drac030]

Basically, DOS XE allocates a buffer to hold *entire* VTOC. One such buffer per drive. So if a disk has 16 MB, the VTOC buffer takes 8k RAM. If there are two such disks, you have 16k less.

 

If SpartaDOS X was this effective, my Atari would need 128k exclusively for the buffers.

 

Surely the DOS XE filesystem does have potential. Still, there is a limit: a file cannot be bigger than ~366 KB.

[flashjazzcat]

Basically, DOS XE allocates a buffer to hold *entire* VTOC. One such buffer per drive. So if a disk has 16 MB, the VTOC buffer takes 8k RAM. If there are two such disks, you have 16k less.

 

If SpartaDOS X was this effective, my Atari would need 128k exclusively for the buffers.

 

Surely the DOS XE filesystem does have potential. Still, there is a limit: a file cannot be bigger than ~366 KB.

Yikes. Would have been nice and quick if the VTOC buffer had been held in an extended bank, but other than that the system has the hallmarks of out and out lunacy. Coupled with the sector link DOS 2.x system, and the wasteful clusters of DOS 3 and 4, it's hard to know what Atari were thinking at the time.

Edited July 22, 2010 by flashjazzcat

[LYNXGUY]

Assem is DOS 3 the only image you want ??

[sup8pdct]

Basically, DOS XE allocates a buffer to hold *entire* VTOC. One such buffer per drive. So if a disk has 16 MB, the VTOC buffer takes 8k RAM. If there are two such disks, you have 16k less.

 

If SpartaDOS X was this effective, my Atari would need 128k exclusively for the buffers.

 

Surely the DOS XE filesystem does have potential. Still, there is a limit: a file cannot be bigger than ~366 KB.

 

Dos XE treats 128 byte sector disks as 2 sector clusters, so it is reasonable to assume that maybe 2 or more 256 byte sectors could be treated as cluster, but finding out how may never happen. I came up with dos xe formatter but once I found out about the vtoc issue, I gave up.

 

James

[sloopy]

--snip--

I also agree that it's a shame that DOS 3, 4, and DOS-XE (the latter because it was released far too late) failed to break the trend of the terrible diasy-chain DOS 1/2.0/2.5 file system. Even MyDOS - which I admire in every other way - perpetuates it, and across hard disk partitions at that.

 

wasnt 2.5 released due to all the problems and public backlash of 3? and was named as such cause it was an enhancement of the 2.0 linage...

 

sloopy.

[flashjazzcat]

wasnt 2.5 released due to all the problems and public backlash of 3? and was named as such cause it was an enhancement of the 2.0 linage...

I believe this was the case.