QL internal 27C512 ROM adapter board

[Marcel_X]

I'm in the process of bringing my old QLs to life again. I got three of them and each has a different ROM. I've got a JM, a JS and an AH ROM in a ceramic package with a "golden" cover! One of them is an issue 6, the other two an issue 5.
So I thought the best thing to do was to upgrade all of them to the latest Minerva ROM. or are there better solutions?

But I couldn't find a proper PCB for a standard 27C512, so I made one myself. Just quick and dirty. No fancy ROM switching. It has a decoder that only decodes #CE on accesses to the first 48K, so the external ROM port doesn't clash with the internal ROM. I found a mICE, plugged it in and everything seems to work just fine! No magic smoke..!

With the new Minerva ROM I can finally see that my FrankenQL is working.
(viewtopic.php?t=2624&hilit=82s123)
It reports 128K or 512K depending on a switch that is located at the rear of the QL. I bought this QL decades ago and the previous owner did the mod.

FrankenQL

But oddly enough, this QL has been running with a Trump card with the full 896K of RAM with the switch in the 512K setting! I can only tell the difference with the Trump card unplugged. With the Trump card fitted it reports 896K regardless of the switch state. So with the internal RAM mod, I guess my RAM is double buffered

Anyway... To make a long story short, I have a few PCBs left, because I only need 3 or 4 of them. If anyone is interested, let me know. I can put them on www.sellmyretro.com.
I have a few 27C512s, so I can burn the ROM of your choice.

[samwisethecat]

I don't suppose that you still have any boards left for you?

https://github.com/stephen-usher/Sincla ... l-Diag-ROM

Has just been released as v1.0 and id love to get it up and plugged into mine to help see what's wrong

[janbredenbeek]

This is the famous 'Spanjer' RAM expansion, named after the father and son who supplied (and optionally fitted) it.

They soldered out the old 64K chips, fitted 256K chips, and added a bit of extra logic (74LS157 multiplexer and PROM for address decoding). The result was 512K internal RAM, which could be disabled by a small switch on the back (it was connected to a line on the PROM which activated the original address decoding).

No surprise that your Trump Card still works with it, it's still internal RAM connected to the ZX8301 with all its drawbacks. Your Trump card simply conceals it with its own RAM, which is on the CPU side of the bus.

(I can supply the schematics if you're interested).