Re: Software for MS-DOS 1.25

From: Michał Pleban <*lists_at_michau.name*> Date: Thu, 12 Oct 2017 13:22:33 +0200 Message-ID: <59DF5079.3030205@michau.name> · lists_at_michau.name

Michał Pleban wrote:

> Well, looks like I was too quick. I was sure that the memory wraps, but
> it doesn't. So $B0000 is an empty space, not a map of $30000.

Just a thought after looking at the schematic. The memory page to be
accessed from the 8088 is selected using signals BP0-BP3 on the external
memory connector in the 710.

How about placing a simple GAL here (maybe even on a small board that
goes between the mainboard on the 8088 board, so that the original
boards are not modifies) which changes $C to $4? This would make the
upper 64 kB at segment 30000 appear also at B0000, while also leaving
the rest of space between 40000 and AFFFF empty as it is now.

Regards,
Michau.

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