Who can tell me more about this COM256?

By Briqunullus

Champion (341)

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17-09-2020, 18:10

While searching for odd MSX-DOS versions I came across this COM256 program. It seems to offer some bank switching / multitasking system for machines with 256K or more. I don't have any clue on how to operate this.

When viewed in a hex editor it turns out to be a modified COMMAND 1.11 (Hal-F edition, the one with the bug), with some extra code at the end. There are no extra commands. I tried renaming it to command.com but that wasn't a success. It starts twice and then hangs.

I found it at the MSX Nostalgia site as disk 174. Who can tell me more about its origin and purpose?

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By Briqunullus

Champion (341)

Briqunullus's picture

31-10-2020, 10:10

I have found out what this modified MSX-DOS can do. The bank switching mechanism is used when copying files. It increases the buffer size, allowing for more files to be read per run. If you only have one drive, this decreases the amount of disk swaps.

So a very clever hack, but of limited use. Still wondering who made it though. By the way, I have also found the 128K version of it. This seems to use VRAM as well for obtaining 4 memory banks.