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Re MS-DOS7 bug, Patch done! available soon :=) (Miscellaneous)

posted by Ninho(R) E-mail, 24.11.2009, 18:10

>> It consists of a fake DOS device driver, that when installed takes 368
>> bytes, does NOT hook any interrupts or DOS function. All it has to do is
>> sit there to offer space for the fake TSRinfo table during Sysinit.

> Okay, sounds like a working solution.

Yay.

> How do you remove the TSR after CONFIG.SYS?

You don't! That's the beauty of the thing (simple=beautiful), it just works!
After MSDOS 7 is finished initialising DOS device drivers from Config.sys, it switches to using its own allocated block for mainaining the TSRInfo structure. The list is built properly including info for those TSRs which were loaded by Wrapper.sys (with my hack loaded of course).

And I have now checked not only DOS 7, Windows 98 can be loaded and work as designed on top of this tower ! Yeepee !

As for the memory eaten up by my solution, well it's only 368 bytes (and can be loaded in UMBs, if available, by DEVICEHIGH). Note it is only /once/ 368 bytes however many TSRs are subsequently loaded using Wrapper.sys or similar. The memory is not needed after driver init is finished - so it /could/ be unlinked from the device driver chain and made available for allocation to DOS programs, by manipulating the MCB chain. But it is so small a patch of memory lost in the middle of DOS drivers area that I don't think the "return on investment" of a specific unloader is worth it (when my little thing is released for "beta" testing, you are welcome to write one however ;)

> How does your version check identify
> the offending MS-DOS versions?

First, let it be remarked that since this program is only ever of use on Win-DOS 7 or 8, and advertised as such, a user /should not/ try to load it under an offending DOS !

However I'll do my best effort to identify genuine MS-DOS from Windows 9x/ME and I hope for you guys to check it works against those non MS DOSes which lie about their "true" ver including :

> PC-DOS, (E)DR-DOS, FreeDOS, PTS-DOS and ROM-DOS do that for sure.
...

> what if MS-DOS 9.50 removed support for, say, UMBs?

DOS ver 9 is the OS2 'compatibilty box' IIRC. It is not likely there will ever be an MS-DOS 9.50 (nor any MS-DOS ver over 8, for that matter)

Cheers

---
Ninho

 

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