You could have a physical witch to connect /WR. If you tie it to 5V it can’t be written. A mechanical pull-up.

May I propose thinking about this in a slightly different way? What if instead of a flash IC (20 year retention guarantee) you used a 128K low power SRAM and CR2032 battery as back-up power? In standby, the SRAM would retain contents using microAmps. The battery would last 15 or 20 years. If you spl...

Though I can't think of a use case where someone would use a QL-SD and want a Miracle hard drive.

It's not the first QL hardware to program its own flash, but it will be the first released hardware, yes.

I have programmed flash off the QL bus, during multi-tasking, without problems. If you recall my idea a few years ago of having multiple CPUs mapped through dual port SRAM to areas of the QL's memory map, I did a fair amount of work on it. I ended up using a small flash as a persistent system-progra...

If I had to pick a machine that was most line the QL, I would pick the Coleco Adam. Similarities: Both have two CPUs. The Adam 2nd CPU, used for system IO and memory management, is a 6801 - a small ROM microcontroller version of the 6800. In the QL, it's an 8049. Both communicate through an internal...

XorA wrote:I wonder if this could be QL related purchase?

Tease.

I don't have any miniplanes left, sorry. I did a 128K battery backed SRAM with write protection a few years ago, for my own personal use. I'll dig it out. It sounds exactly what you need. If I can find the PCB files, I'll publish them. It used two 628512 to implement 896K, with the top 128K write pr...

Mini-ITX cases do not work for any currently available QL or clone.

The Q68 can be bodged into anything, but "bodge" is the operative word and a mini-ITX case is still massive overkill for the Q68.

It does sound like the power supply. You plug the keyboard in and it delivers the extra current, but then after a few seconds it hits the thermal limit and starts current limiting?