[Speccy] Didaktik Gama emulation
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iwu...@gmail.com
Nov 7, 2015, 12:17:24 PM11/7/15
to EMUL8
Greetings,
as an owner (from ~1990) of this machine I must say that emulation of this machine is not implemented correctly.
Gama has additional 32kB of RAM and Intel 8255 interface which is also used for memory bank switching - using OUT 127,bank (0 or 1).
as an owner (from ~1990) of this machine I must say that emulation of this machine is not implemented correctly.
Gama has additional 32kB of RAM and Intel 8255 interface which is also used for memory bank switching - using OUT 127,bank (0 or 1).
fms
Nov 10, 2015, 10:19:25 AM11/10/15
to EMUL8, iwu...@gmail.com
I have not been able to implement this correctly, since I could not find complete information on the bank switch and the test programs to debug it. If you have information and the test software, please contact me via email.
iwu...@gmail.com
Nov 12, 2015, 8:55:21 AM11/12/15
to EMUL8, iwu...@gmail.com
Bank switching is explained (in Czech) here: https://cs.wikipedia.org/wiki/Didaktik_Gama
The ROM of models '88 and '89 contains routines for bank switching in BASIC programs. Model '89 has also driver for Centronics-printer in ROM.
The switchable area resides from 32768 to 65535 and because BASIC programs can occupy space in this area setting RAMTOP to this area caused system crash on earlier (model 87) variants of the machine when switching banks. This problem was fixed in model '88 of the machine so when executing OUT 127,x (0 or 1) data from 32768 to RAMTOP are copied between banks.
There is not a lot of programs designed for this feature: Gama Copy 1, 2 (tape-copy utilities by R. Gemrot), Gama Copy 80 (similar utility by Busy), and a few tools for Didaktik 40/80 floppy drive.
The ROM of models '88 and '89 contains routines for bank switching in BASIC programs. Model '89 has also driver for Centronics-printer in ROM.
The switchable area resides from 32768 to 65535 and because BASIC programs can occupy space in this area setting RAMTOP to this area caused system crash on earlier (model 87) variants of the machine when switching banks. This problem was fixed in model '88 of the machine so when executing OUT 127,x (0 or 1) data from 32768 to RAMTOP are copied between banks.
There is not a lot of programs designed for this feature: Gama Copy 1, 2 (tape-copy utilities by R. Gemrot), Gama Copy 80 (similar utility by Busy), and a few tools for Didaktik 40/80 floppy drive.
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