Dave wrote:Like a 68000 in a 68008 adapter, where you have even/odd bytes that you can just latch, the 68020 has dynamic bus sizing and the PiStorm software treats it as always a 16 bit transfer. It would honestly be easier to just redo the Gold Card PCB with a full DIP adapter and transfer the components across. You’d be able to omit the DRAM entirely, funnily enough.
So you'd have two layered board where one interfaces with the QL and the other with the board so to keep the PiStorm relatively unchanged. That would work if you had a Gold Card. Unfortunately I don't but I'm hoping that Altera chip can be programmed to handle some of that. What does the Gold Card use?
I do think a good interface to the QL would be a similar card to the Gold Card that connects to the expansion slot since putting it on top of the processor may not leave much room to close the lid...I suppose you could use a ribbon cable to let the Pi Zero 2W float around.
I suppose the easiest approach is to make a PLCC-84 to DIP-64 adapter? This would also allow the FPGA board and Pi to be outside the QL case, over the floppy interface. The Pi/FPGA do draw more power than the QL can supply, so it would be best if the stack were externally powered with the GC on a single supply.
How do you externally power a device hooked to the processor without it getting back to the board. That's an issue with the A600 PiStorm and you need to grab 5 volts internally from the floppy 5 volt connector (i.e. it's not powered externally). Is there 5 volts available on the QL that's enough to power the Pi? The Raspberry Pi Zero 2W needs between 260 to 370 milli amps and you add to that however much the PiStorm board needs.
Edit: I would think since there is enough amps to power up to 6 external, motor-driven microdrives (whatever voltage they use) so somewhere could grab a small amount of power.
The expansion connector supplies 9V to expansions. The Sinclair spec limits draw to 500mA, which is not enough to run a Gold Card *and* a Pi 3. It's barely enough to run a Gold Card. My hungriest card that works on the QL with original power supply and 7805 draws 625mA.
The GC and SGC can be powered externally. SGC has official provision for this, and Tetroid's Gold Card gets around it by using a much more efficient buck regulator circuit. I think as long as a ground link were added to match the secondary power supply's ground to the QL's ground as close to the expansion port as possible, it would be functional. As long as both supplies share a common ground and the power is switched together, no problems/damage should result. Maybe a blocking diode on the power line out of the QL would be a good idea so the GC couldn't backfeed the QL?
If the PiStorm can replace a 68020, then things certainly get more interesting.
It would be helpful to know if the INGOTs Tetroid is producing for the GC and SGC contain the same code. I don't know if Tetroid has access now, considering the situation.
Trying to find out how much the PiStorm board (Altera II Max) draws but the Pi Zero 2W seems to be pretty efficient for the power it supplies and is becoming the preferred choice for PiStorm boards since it's only slightly less powerful.
bwinkel67 wrote:Trying to find out how much the PiStorm board (Altera II Max) draws but the Pi Zero 2W seems to be pretty efficient for the power it supplies and is becoming the preferred choice for PiStorm boards since it's only slightly less powerful.