The Sinclair QL Forum

I thought I'd split this out into it's own thread as am still keen to find a solution

My plan is to cut the ROMOEH line at the rear of the socket (as per image) and fit a switch to the case (not concerned about making the hole as already have a switch fitted for the JS/Minerva Mk2 ROM Switcher in this QL)

Dave mentioned I'd need a 100ohm resistor, but I've no idea where the resistor needs to go from/to please?

I was also looking into software solutions as well because the Minerva Mk2 has the nice option to mask out ROMS at boot
The problem is there's plenty of software, mainly games I guess, that just won't run on Minerva so I prefer JS (also it would be a pain to re-enable the port with QIMSI disabled, though easy to disable it)

But I don't want to use modified ROMS (especially as it took so much trouble to get the MK2 ROM switcher working and it can't be reprogrammed or extracted) and prefer to keep them original anyway

I did consider a modified JS ROM image to boot using the SGC utility to boot any ROM image (ideal as it's a 1 shot disable of the ROM port), but then I have the problem of software that doesn't like SGC and more especially controlling the speed of the SGC seems very hit and miss depending on how the software was written. Also I don’t plan to keep the SGC in this QL anyway

I'd really like a solution that's either internal to the QL or Software based

I was wondering if anyone has any thoughts please?

Many thanks
Tony

I may of just had a light bulb moment

This is more about where I need to remove the whole QIMSI as for most games that have a problem with QIMSI being there then just removing the SD card is enough

Maybe I could use QIMSI gold instead on this QL and swap the SD to one containing a dummy $C000 ROM

(FROM THE QIMSI Manual) If a file named QL_ROM.SYS is present on the SDHC card, it will be loaded at address $C000 into the ROM area of the QL (and not the MiniQ68). The maximum allowed ROM length is 16 KB. The default ROM with the SD card driver will be replaced if a QL ROM image is loaded from card

Will give it a go

t0nyt wrote: Tue Sep 09, 2025 10:04 am Maybe I could use QIMSI gold instead on this QL and swap the SD to one containing a dummy $C000 ROM

That is one possibility. You could rename a toolkit of your choice to QL_ROM.SYS and copy it to the card, or a file containing just $FF.
If a legacy QIMSI is updated to the latest FPGA logic, it will also have this feature.

I also have an FPGA variant for QIMSI Gold where the ROM area at $C000 is always empty, and which emulates 48 KB ROM at $0 instead. So one could change Minerva vs QDOS by SD card image. The problem with that: Some QLs come out of power-on reset too quickly for the ROM at $0 to be read from SD card. In that case, a manual reset is needed (or a modification of the reset capacitor).

Peter wrote: Tue Sep 09, 2025 10:44 am That is one possibility. You could rename a toolkit of your choice to QL_ROM.SYS and copy it to the card, or a file containing just $FF.

Thanks Peter, will give this a try then

Peter wrote: Tue Sep 09, 2025 10:44 am If a legacy QIMSI is updated to the latest FPGA logic, it will also have this feature.

That's good to know, would rather use the QIMSI Gold as intended in the long term

Many thanks
Tony

t0nyt wrote: Tue Sep 09, 2025 9:34 am I thought I'd split this out into it's own thread as am still keen to find a solution

My plan is to cut the ROMOEH line at the rear of the socket (as per image) and fit a switch to the case (not concerned about making the hole as already have a switch fitted for the JS/Minerva Mk2 ROM Switcher in this QL)

Dave mentioned I'd need a 100ohm resistor, but I've no idea where the resistor needs to go from/to please?

In the QL World of 1986, November, in page 46, it's explain how to install a switch on a ROM cartridge to disable it, you can see the resistor on the disconected pin to Vcc, similar can be applied internally on the ROMOE line, just tie the resistor to GND (because of the NAND gate that invert the signal).
In the schematic is not very clear but C is the common pin of the switch, and A/B are the N.C./N.O. pins.

So the idea is in one position you link the cartridge signal to the internal ROMOE, and in the other position you leave on air ROMOE and link the pin of the port cartridge to GND, in this way the cartridge is never activated.

Many thanks Alvaro!

Will give it a go as soon as I get a chance

Many thanks
Tony

Hi!

Just... cause I always want to keep intact all QLs... Why not to use an adapter where you solder the resistor and the Switch?
Do you know what I mean?

QL_ROM_PORT == ADAPTER == QIMSI
It should not be difficult at all with breadboard or similar.
If you prefer something more refined, I could do it the Gerber for you.

Pros: You can use the adapter in any other QL without mod them. You preserves intact your QLs
Cons: I don't see any cons.

Cheers

Popopo wrote: Thu Sep 11, 2025 9:25 am Hi!

Just... cause I always want to keep intact all QLs... Why not to use an adapter where you solder the resistor and the Switch?
Do you know what I mean?

QL_ROM_PORT == ADAPTER == QIMSI
It should not be difficult at all with breadboard or similar.
If you prefer something more refined, I could do it the Gerber for you.

Pros: You can use the adapter in any other QL without mod them. You preserves intact your QLs
Cons: I don't see any cons.

Cheers

Thanks Popopo, all good points

But this QL is already hacked around (lower case already has switch for JS/Minerva Mk2 switching & a gap at rear for I2C cable, and the upper case is modified for Schon keyboard)

Also, the cut pin could easily be soldered back together I guess

Thanks
Tony

You are welcome