Spectrum Computing

Hi all,

I have several ZX Spectrum, from 48K to the 128K and my 128 +2B has a weird behaviour.

If turn on with the divmmc future, works perfectly. I can play, etc.

If turn on without the divmmc the image appears with squares, garbled.

Is it a ROM problem? He has the 40092U and 40093U inside.

Has any one experienced this?

Best Regards
Pedro

DivMMC, the regular one, starts by copying the ROM to internal DivMMC memory.
I'm not sure the DivMMC Future does the same, but it probably does since it's a feature of the DivMMC OS.

It could in fact be a ROM problem, but due to what I said above, I doubt it.

It might be related with memory (RAM), or some component, only works well enough, if the extra load on the power supply is present.
For example, having the power rails a bit out of spec (too high voltage).

I have never seen this issue myself, and I'm intrigued.

I'm going to measure the supply rails.

But even the tape games load perfectly.

The only thing that doesn't seem to work is the default OS.