128K +2 Works with divmmc but alone not

For experts to discuss very technical stuff and newbies to ask why the Spectrum they bought off ebay doesn't work.
Post Reply
PedroSilva
Berk
Posts: 2
Joined: Fri Aug 10, 2018 6:02 pm

128K +2 Works with divmmc but alone not

Post by PedroSilva » Fri Aug 10, 2018 6:07 pm

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
0 x

User avatar
RMartins
Manic Miner
Posts: 331
Joined: Thu Nov 16, 2017 3:26 pm

Re: 128K +2 Works with divmmc but alone not

Post by RMartins » Fri Aug 10, 2018 7:07 pm

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.
0 x

PedroSilva
Berk
Posts: 2
Joined: Fri Aug 10, 2018 6:02 pm

Re: 128K +2 Works with divmmc but alone not

Post by PedroSilva » Sat Aug 11, 2018 7:25 pm

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.
0 x

Post Reply