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QL internal 27C512 ROM adapter board
Posted: Wed Feb 26, 2025 1:07 pm
by 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.
Re: QL internal 27C512 ROM adapter board
Posted: Mon Jun 23, 2025 5:36 pm
by 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
Re: QL internal 27C512 ROM adapter board
Posted: Mon Jun 23, 2025 10:15 pm
by 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).
Re: QL internal 27C512 ROM adapter board
Posted: Tue Jun 24, 2025 5:13 pm
by Popopo
Hi Marcel
Marcel_X wrote: Wed Feb 26, 2025 1:07 pm
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
What do you mean with double buffered?
Another question, that QL has internal memory upgrade. Do you have another ram IC of that type faulty?
I would appreciate some RAM testing.
Thanks.
Re: QL internal 27C512 ROM adapter board
Posted: Tue Jun 24, 2025 5:18 pm
by Popopo
Hi!
janbredenbeek wrote: Mon Jun 23, 2025 10:15 pm
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).
Is that one what I have described in my github?
link to my repo
Looking for people with those machines or variants to get pictures. In case some of them were faulty, to check them in order to repair them.
janbredenbeek wrote: Mon Jun 23, 2025 10:15 pm
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.
What do you mean with "CPU side of the bus and Trump conceals it with its own RAM?
I thought they just place them in free addrs zone
Thank you
Re: QL internal 27C512 ROM adapter board
Posted: Tue Jun 24, 2025 9:55 pm
by aalea
janbredenbeek wrote: Mon Jun 23, 2025 10:15 pm
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).
Please provide any details you can about this 'Spanjer' RAM upgrade, I like to check it.
Re: QL internal 27C512 ROM adapter board
Posted: Tue Jun 24, 2025 10:37 pm
by janbredenbeek
Popopo wrote: Tue Jun 24, 2025 5:18 pm
Is that one what I have described in my github?
link to my repo
Looking for people with those machines or variants to get pictures. In case some of them were faulty, to check them in order to repair them.
Probably something similar; here are the schematics:
Popopo wrote: Tue Jun 24, 2025 5:18 pm
janbredenbeek wrote: Mon Jun 23, 2025 10:15 pm
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.
What do you mean with "CPU side of the bus and Trump conceals it with its own RAM?
I thought they just place them in free addrs zone
If the Trump card is present and the CPU addresses anything over $40000, DSMCL is asserted which disables access to the internal RAM. Hence, the CPU only sees the Trump card RAM and isn't slowed down by RAM accesses from the 8301.
Re: QL internal 27C512 ROM adapter board
Posted: Tue Jun 24, 2025 11:03 pm
by Derek_Stewart
looks good, but, QL RAM QuintupLer by CHR$ is better:
viewtopic.php?p=51306#p51306