Monthly Archives: March 2020

This weekend the German ZX meeting was supposed to happen, but for some pandemic reason it didn’t. Which is very unfortunate because not only did I produce a batch of QL-VGAs for it, I also had a secret product in development that I wanted to reveal there: QL-SD ROM. Please note that everything I write about here is in early development (maybe including the name), as a matter of fact after weeks of problems and lack of time it only started working yesterday!

So what is it? QL-SD ROM is an external QL-SD variant for the ROM port. That by itself is already pretty cool I think, but has basically been done before using a carrier board and the internal QL-SD variant. No, what I’m really excited about is that this board combines the functionality of QL-SD and the ROM switcher, i.e. it also has 512kb of flash on board that can contain up to 8 different operating systems.

“But the ROM switcher already exists, too” I hear you say, “what’s the innovation here?” Well, for starters, there are no DIP switches, this is true bank switching that is controlled by software, so a few more interesting usage scenarios become possible.

And that is not all, the main difference is that the QL can reprogram the flash itself, no external hardware necessary whatsoever! I think this is a first. Where supplying fixes for the QL-SD is a pain because it involves bending pins and reprogramming an EEPROM using specialized hardware, this QL-SD variant can update the OS or its driver using a simple BASIC command.

By default the QL always boots into slot 0 as slot 1-6 can only be selected using software. “But what if I want to boot into a different OS by default, what do I do then?”. Well, you simply flash that OS into slot 0 of course! It only takes a few seconds after all.

“But what happens if something goes wrong during the update?” you might ask. Well, there is a jumper on board that makes QL-SD use OS slot 7, which is some sort of “recovery slot” that should only be used to make slot 0 work again.

All this of course only works when the internal ROMs have been removed as otherwise the two devices would be fighting over the data bus. For people not wanting to open the QL at all there is also a “no OS” jumper that makes QL-SD leave the OS area alone so the ROM is only used for the extension slot. In this case the flash is not as useful but at least the driver can still be updated.

Well, that’s it for now. Remember, this is far from a finished product, it’s not even sure it will ever be one. But I’m currently very elated that everything finally works so I wanted you to share the joy 😉 Here are a few pictures, enjoy.

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