Re: Amtech RF512C DOS: differences to 1571 ROM (was: Amtech RF512C manipulates reading the ROM image with M-R)

From: Rhialto <>
Date: Thu, 7 Oct 2021 14:14:46 +0200
Message-ID: <>
On Wed 06 Oct 2021 at 16:32:17 +0200, Spiro Trikaliotis wrote:
> Thus, they did not only patch the drive to not read back the $FFxx area,
> they even did it in a very stupid way, patching out the checksum
> functions instead of fixing the checksum.
> Did they really know what they were doing?

I would say no: because their change to M-R does not really hide very
well that they copied the ROM. It hides just a very small part of it.
Maybe they meant to hide the whole ROM, but failed to do so.

It's a bit like the old PET ROMs where Microsoft put code in the PEEK()
function to disallow reading the ROM area (or at least the BASIC part);
it always returns 0 (that is why programs test PEEK(50003) which
happens to be 1 in "new ROMs").

> Spiro
___ "Buying carbon credits is a bit like a serial killer paying someone else to
\X/  have kids to make his activity cost neutral." -The BOFH    falu.nl_at_rhialto

Received on 2021-10-07 15:00:03

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