IS-DOS

Hello, Nickolay Zabrodotsky! I remember, on Oct 23, 97 you took it and launched it at me with this:

NZ> Is it possible to install CP/M on the Pentagon (that is, on a computer
NZ> that does not contain it in ROM)?
NZ> Sincerely, Nickolay.

A pro won’t contain it in ROM either. By the way, the modification has been flying here for a long time. The feature
is to organize 4 bits of the #DFFD port, which connects the RAM page to
in place of ROM 0, as well as bit 5 of it, when activated
with the 4th bit of port #7FFD reset to 0, the VG93 ports were enabled for access from
RAM (in this case, instead of #FF it should become #BF). In that scheme, it was true
it was a little simplified: bit 5 #DFFD was not there, and bit 4, in addition to cutting off the ROM
also included VG93 ports for access from RAM. But in Pro it was done exactly as I
said.

Bye, with all the best wishes, Pavel Fedin.