MS-DOS version 6 differences

[Ole Juul]

Does anybody know what the difference is between the different MS-DOS 6.* versions?

I'm not interested in the utilities like DoubleSpace and DriveSpace, but just the kernel files. Although I expect 6.21 would be a little smaller as it might not have reference to either one of those in the kernel. I looked at three versions that I had handy and found the files to be different sizes, so that implies some difference - but what?

Here are the sizes and dates:

              6.0 - 3/10/93  6.2 - 9/30/93  6.22 - 5/31/94
IO.SYS          40,470         40,566         40,774 bytes
MSDOS.SYS       38,138         38,138         38,138 bytes
COMMAND.COM     52,925         54,619         54,656 bytes

PS: I just found a copy of 6.21 but it has the same sizes as 6.22 although the date is 2-13-94.

 

[Agent Orange]

Does anybody know what the difference is between the different MS-DOS 6.* versions?

I'm not interested in the utilities like DoubleSpace and DriveSpace, but just the kernel files. Although I expect 6.21 would be a little smaller as it might not have reference to either one of those in the kernel. I looked at three versions that I had handy and found the files to be different sizes, so that implies some difference - but what?

Here are the sizes and dates:

              6.0 - 3/10/93  6.2 - 9/30/93  6.22 - 5/31/94
IO.SYS          40,470         40,566         40,774 bytes
MSDOS.SYS       38,138         38,138         38,138 bytes
COMMAND.COM     52,925         54,619         54,656 bytes

PS: I just found a copy of 6.21 but it has the same sizes as 6.22 although the date is 2-13-94.

Ole: I use 6.2 - never had a copy of 6.22. IIRC, the major difference in 6.22 was a fix for the DoubleSpace compression program.

 

[Chuck(G)]

Well, 6.22 IIRC replaces the Doublespace program with Drivespace, because of the loss in litigation over patent infringement to the owners of Stacker (Stac Electronics).

What was interesting that only one edition of the MSDN library contains the explanation of how Doublespace worked; it was deleted after the Stac litigation.

 

[Ole Juul]

Ole: I use 6.2 - never had a copy of 6.22. IIRC, the major difference in 6.22 was a fix for the DoubleSpace compression program.

It was a copyright thing where MS got caught illegally distributing DoubleSpace. They were forced to stop doing that, but soon came up with their own called DriveSpace. 6.0 and 6.20 had the DoubleSpace utility sold with it, 6.21 had no disk compression, and 6.22 came with a copy of the non-infringing DriveSpace.

Why the kernels have different sizes is something I don't know how to research. I'm hoping one of our programmers here has some insights.

 

[Chuck(G)]

It was a copyright thing where MS got caught illegally distributing DoubleSpace. They were forced to stop doing that, but soon came up with their own called DriveSpace. 6.0 and 6.20 had the DoubleSpace utility sold with it, 6.21 had no disk compression, and 6.22 came with a copy of the non-infringing DriveSpace.

It absolutely was not a copyright thing--it was an infringement on Stac patents 5016009 and 4701745 (USPTO). Microsoft had talked to Stac about licensing the Stacker technology, had examined their code, but never carried through and brought out Doublespace, instead. That was so bald-faced an infringement that MS didn't have a chance with a jury. Pure bush-leage hijinks that cost Microsoft about $120M and MS was ordered to recall every copy of MSDOS 6.0 that had been distributed.

Hence, the free "step-up" package, which probably satisfied no one.

I'm going to guess that the kernel differences have something to do with that.

 

[krebizfan]

I remember there being a couple of odd bugs with disks of certain sizes which got fixed in DOS 6.2 but I can't track down a reference to them.

The new functionality in DOS 6.2 that would most likely be in command.com, io.sys or msdos.sys would be the automatic loading of doublespace if a compressed floppy was inserted; the "/Y" switch for command.com, and prettier output of large numbers by functions like DIR. DOS 6.2 also included a major fix to DoubleSpace. I also noticed a reference to a "DIR /O:C" option which lists files by compression ratio. I guess that could collectively account for much of the extra 2KB in file size.

DOS 6.22 included functionality to load both drivespace and doublespace to handle legacy compressed disks. I don't think I ever tried it with disks from both compression methods.

Oddly, I have a copy of a product called "DoubleTools" which are utilities specific to only DOS 6.0's implementation of DoubleSpace; they do not work with DOS 6.2 or DOS 6.22.

 

[krebizfan]

It absolutely was not a copyright thing--it was an infringement on Stac patents 5016009 and 4701745 (USPTO). Microsoft had talked to Stac about licensing the Stacker technology, had examined their code, but never carried through and brought out Doublespace, instead. That was so bald-faced an infringement that MS didn't have a chance with a jury. Pure bush-leage hijinks that cost Microsoft about $120M and MS was ordered to recall every copy of MSDOS 6.0 that had been distributed.

Microsoft had licensed a competing product with its own patent. The court ruled that the Stac patent covered the patent that Microsoft tried to use. The jury ruled Microsoft's infringment not willful but the injunction forced Microsoft to settle instead of appealling all the way up. If disks created in one version of DOS can't be read by a slightly later version, sales will cease.

 

[Chuck(G)]

Just so--but it had nothing to do with copyright. They saw the Stac software, were aware of the patents and licensed an infringing product anyway. Incredibly stupid move. The proper thing to have done would have been to hire an outside firm with all the appropriate NDAs in place to perform the evaluation and acquisition, so that until the ink was dry on a license, Microsoft would have no idea what was in any product, nor how it worked.

 

[Ole Juul]

It absolutely was not a copyright thing--it was an infringement on Stac patents 5016009 and 4701745 (USPTO). Microsoft had talked to Stac about licensing the Stacker technology, had examined their code, but never carried through and brought out Doublespace, instead. That was so bald-faced an infringement that MS didn't have a chance with a jury. Pure bush-leage hijinks that cost Microsoft about $120M and MS was ordered to recall every copy of MSDOS 6.0 that had been distributed.

Hence, the free "step-up" package, which probably satisfied no one.

I'm going to guess that the kernel differences have something to do with that.

Thanks for the clarity. I was obviously a bit rough in my understanding there.

krebizfan: DOS 6.22 included functionality to load both drivespace and doublespace to handle legacy compressed disks.

So I wonder if I could assume that outside of drivespace and doublespace, one would be just as well off with version 6.0. I'm assuming that the "odd bugs with disks of certain sizes" would relate to the compression as well.

 

[Caluser2000]

I remember there being a couple of odd bugs with disks of certain sizes which got fixed in DOS 6.2 but I can't track down a reference to them.

I think there were issues with folk reporting data corruption using disk compression and 6.2 introduced DoubleGuard to provide real time protection on DoubleSpaced partitions to protect against the data corruption. IIRC it shut down the system in severe cases. Also ScanDisk was introduced I think.

There's a whole heap of stuff with regards to using and maintaining MS disk compression at http://suttonsolves.com/ds_faq.html

 

[krebizfan]

I think there were issues with folk reporting data corruption using disk compression and 6.2 introduced DoubleGuard to provide real time protection on DoubleSpaced partitions to protect against the data corruption. IIRC it shut down the system in severe cases. Also ScanDisk was introduced I think.

Data corruption with compressed disks was one issue. The other issue was that disks could be created with clusters whose numbers corresponded with reserved values ensuring files written out there would not be read. The fix was simply to keep the number of clusters lower than the various end of file chain values. This applies to both compressed and uncompressed disks. Well, that is what I remember but it has been 20+ years and I can't find a reference to confirm it.

 

[Ole Juul]

I think there were issues with folk reporting data corruption using disk compression and 6.2 introduced DoubleGuard to provide real time protection on DoubleSpaced partitions to protect against the data corruption. IIRC it shut down the system in severe cases. Also ScanDisk was introduced I think.

Thanks for reminding me about ScanDisk. I thought it was much older, but then I don't generally use it. I always disliked the message you get which say to "try ScanDisk" whenever Chkdsk is run, because I run Chkdsk for different reasons. Arrggghh! This advertising within an OS bugged me when it came out, and still does. I checked on the net and indeed Scandisk came out with version 6.2.

I first checked my little PCRef book because it says "first introduced" under every DOS command. Scandisk wasn't there! So I looked in the front and now see that the book was current with version 6.0 and it says right there in a bold face editor's note:

If you are using Version 6.0, it is strongly recommended that you do not use DOUBLESPACE or SMARTDRV. Both of these programs cause a variety of problems with hard dirves and are not safe to use.

 

[Caluser2000]

Data corruption with compressed disks was one issue. The other issue was that disks could be created with clusters whose numbers corresponded with reserved values ensuring files written out there would not be read. The fix was simply to keep the number of clusters lower than the various end of file chain values. This applies to both compressed and uncompressed disks. Well, that is what I remember but it has been 20+ years and I can't find a reference to confirm it.

It'll be buried in the MS KB somewhere still I'd imagine. I've got some mags from that era still so will have a gander to see what's in them.

Ole Juul from what I understand a lot of the so called "enhanced" tools, defrag, scandisk et el, were just licenced Nortons stuff anyway. Let's not forget MS was pushing Windows 3.x as much as possible as well. I suspect they where also added to make up for lack of functionality in the standard tool set.

Found this link with regard to smartdrv- http://michaelmaardt.com/dos56/smartdrv.shtml interesting reading.

"SMARTDRV 4.2: Many users complained about losing data because, in all good faith, they had switched off their PCs too soon (before the cache had emptied to disk). As a result, Microsoft ' keeping a low profile and without any public announcement ' released version 4.2 before DOS 6.2, which, like earlier versions, still has a write cache as default but writes to disk before returning to the DOS prompt after closing a program. This facility is new! With this, the user is certain not to lose data ' although a small price is paid in the form of reduced speed"

 

[Chuck(G)]

Reminds me of the business of Ctrl-C at the command prompt.

 

[Ole Juul]

I think krebizfan has given the most plausable answer to my original question (thanks!):

krebizfan:
The new functionality in DOS 6.2 that would most likely be in command.com, io.sys or msdos.sys would be the automatic loading of doublespace if a compressed floppy was inserted; the "/Y" switch for command.com, and prettier output of large numbers by functions like DIR. DOS 6.2 also included a major fix to DoubleSpace. I also noticed a reference to a "DIR /O:C" option which lists files by compression ratio. I guess that could collectively account for much of the extra 2KB in file size.

Chuck pretty much explained it, but go to the end of this page, and there is a fairly complete explanation of the licensing issue and Stac lawsuit. It's quite a convoluted story.

Reminds me of the business of Ctrl-C at the command prompt.

I'd be interested in knowing what you're thinking about. I'm a great fan of Ctrl-C. I also put "break on" in my autoexec.bat, but it rarely works anyway.

 

[Chuck(G)]

Early versions of MS-DOS did not always see when a floppy was changed--sometimes leading to disaster. (360K drives do not have a "disk changed" line and old formatted MS-DOS floppies did not employ a VSN) A Ctrl-C at the command prompt told DOS to forget whatever it thought was in the drives and start fresh. You can find in the early KB where users complained about doing a DIR on a newly-inserted disk and getting the contents of the old one.

 

[Krille]

One of the changes between MS-DOS 6.20 and 6.21 was a workaround for a hardware bug in certain Cirrus Logic chips used in some harddrives. Running a surface scan in Scandisk with DOS set to have VERIFY=ON would erase all data on the drive... Oh, the irony :D

The only mention of this that I can find is this. (I have a bunch of Conner CFS210A drives so I should probably keep using DOS 6.22)

 

[Ole Juul]

One of the changes between MS-DOS 6.20 and 6.21 was a workaround for a hardware bug in certain Cirrus Logic chips used in some harddrives. Running a surface scan in Scandisk with DOS set to have VERIFY=ON would erase all data on the drive... Oh, the irony :D

The only mention of this that I can find is this. (I have a bunch of Conner CFS210A drives so I should probably keep using DOS 6.22)

Speaking of irony. I see I was participating in that thread - but I had completely forgotten.

And that reminds me of that damn drvspace.bin file that used to show up all the time. It didn't do anything if you weren't a fan, so you just had to delete it.