Hugo Holden
Veteran Member
I wanted to try out the Compupro Spectrum board in my Sol. After trying the Matrox ALT-512/256 and the Dazzler I found that BASIC was an invaluable tool, to learn the card's registers, before moving to an 8080 assembly language routine.
I run MBASIC in CP/M and it is a big program, using up half the 48k memory.
I have been running the 64k SCP110 static RAM card, it had an address decoder for disabling applications, but its logic its used up to disable the card above BFFFH. This card though can inhibit 4k blocks of memory. I looked at the Compupro RAM17, but that one has the facility to inhibit the memory for 16k blocks, not leaving enough spare RAM.
To run the Spectrum card, MBASIC and CP/M and still have some area left for transient programs I needed to have the SCP110 card inhibit above 48K (as usual) but also over a 8k range, say from 6000H to 7FFFH, because this is the space or a block required for the Spectrum's RAM, which when the spectrum is not activated, just acts as ordinary system RAM.
I have attached a "memory map" of my SOL. The thing is that I didn't want to modify the SCP110 card or the RAM17 card hardware as they are valuable (to me at least), but I noticed that if I unplugged the jumper on the output of the address decoder on the SCP110 card, I could plug it onto a custom pcb which would deal with the required deactivation of the SCP card over an 8k address range and then I could have no modification to the actual SCP110 card.
I think there is also a way to Phantom the memory out using that line in the SOL, but I struggle with the software, say to integrate that into test programs and a hardware solution seemed suitable, but is there another more simple/easy way to do it than at the hardware level ?
(I didn't have a 74LS640 in my parts box, so I had to use the '642 with some pullups because its open collector)
I run MBASIC in CP/M and it is a big program, using up half the 48k memory.
I have been running the 64k SCP110 static RAM card, it had an address decoder for disabling applications, but its logic its used up to disable the card above BFFFH. This card though can inhibit 4k blocks of memory. I looked at the Compupro RAM17, but that one has the facility to inhibit the memory for 16k blocks, not leaving enough spare RAM.
To run the Spectrum card, MBASIC and CP/M and still have some area left for transient programs I needed to have the SCP110 card inhibit above 48K (as usual) but also over a 8k range, say from 6000H to 7FFFH, because this is the space or a block required for the Spectrum's RAM, which when the spectrum is not activated, just acts as ordinary system RAM.
I have attached a "memory map" of my SOL. The thing is that I didn't want to modify the SCP110 card or the RAM17 card hardware as they are valuable (to me at least), but I noticed that if I unplugged the jumper on the output of the address decoder on the SCP110 card, I could plug it onto a custom pcb which would deal with the required deactivation of the SCP card over an 8k address range and then I could have no modification to the actual SCP110 card.
I think there is also a way to Phantom the memory out using that line in the SOL, but I struggle with the software, say to integrate that into test programs and a hardware solution seemed suitable, but is there another more simple/easy way to do it than at the hardware level ?
(I didn't have a 74LS640 in my parts box, so I had to use the '642 with some pullups because its open collector)
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