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PK Zippers self destruct (Announce)

posted by Ninho(R) E-mail, 10.09.2016, 10:40

> I'm not looking for a solution but
> both the old PKZIP and PKUNZIP
> programs at times self destruct on
> my new I5 system.

> When this happens the size of the
> program will be found to be 65535
> bytes. Yep.

I don't have access to any of the "problem" CPUs to test my idea,
but as a 1st guess, I would suspect those modern Intel CPUs and supporting
chipsets dropped all support for legacy real-mode 'wrap at 1 Meg', A20-gate
etc, stuff - stuff on which a few DOS programs, /especially/ some packers-
unpackers have been known to rely. You could test my hypothesis by ensuring that DOS load the PK(UN)ZIP program ABOVE 64K. If your DOS version has
a "LOADFIX" command, use that - else you could have to stuff harmless TSRs
or resident data in sufficient quantity to pass above the 64k mark before
starting the PKZIP...

I realise you wrote you ain't looking for a solution, so that was just
my 2 cents of mostly useless advice. If you do the suggested test though,
please report whether loadfix or such seemed to fix the issue, or didn't.

EDITED to add : could also check whether the problem is solved by / sensitive to the / presence/absence of EMM386 (which emulates an A20-gate in software).

---
Ninho

 

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