FPGA replacment for the ZX8301 ULA and more

[lliont]

Ok I have already ordered some pcbs of a more compact version of the basic ULA and after testing the new pcb I will order cplds to build some.

[Peter]

That looks nice! I'd definitely like one or two.

[Pr0f]

I think you have a ready market for these I'd like at least one Also happy to have a go at building one if they come out as a kit for the brave tinkerers...

[Peter]

A good compromise might be to have a batch SMD soldered and to add the socket pins manually.

[lliont]

This way it will ship easier, but I have to test them before I ship

[lliont]

Another idea is this:

Replaces both the ULA and the local 128K ram, it is faster and an easy repair if one has problem with the onboard soldered ram, it is also compact.

But needs to be tested because it brings the cpld to the limits of it's capacity and hope I can make the project fit.

[martyn_hill]

Leon, I continue to marvel at your tenacity and creativity

Yes, if there is space for the base 128k RAM, that would be a very effective way to address the most common failures on our QLs whilst still honouring the intention of a pure ULA 'replacement' - especially if the original DRAM access speeds could be enabled by default (to run those pesky legacy QL games), with an option to switch to 'turbo' RAM access speed via a POKE...

I soooo want some of these

[lliont]

Yes there will be a slow mode and a fast mode (I wouldn't call it turbo) this is the easy part.

The clock still the same 7.5Mhz and the Vertical Sync also the same, just less stolen cpu cycles by the video circuit.

This will work for replacing bad ram if the ram chips fail gracefully and don't mess with the bus when not enabled, in another case they will need to be isolated anyway at least their output pins.

Leon, I continue to marvel at your tenacity and creativity

Thanks, It's my hobby.

[Peter]

Another idea is this:
Replaces both the ULA and the local 128K ram, it is faster [...]

This effect is well-known to me... called feature creep

[Andrew]

Will there be a SMSQE version for the FPGA ULA, that will allow the use of 16 colors?