RAM speed issue

[msknight]

I've fitted a couple of zeddies with Alliance AS6C62256 32k ram chips. Memory testing is happy with 16k present and usable by basic.

However, with a 220pF cap fitted it's not enough and if I go one step higher to 330pF I end up losing the left column.

I don't immediately want to write this off as a RAM issue, but I'm between steps here.

Grateful for thoughts and advice.

[msknight]

I just thought to tag a 220pF and 47pF together... and that still resulted in garbage on the screen.

[Lardo Boffin]

I have not had to go above 100pF to get hires working. So far they have worked on 47 to 100pF

[msknight]

I have not had to go above 100pF to get hires working. So far they have worked on 47 to 100pF

Maybe Mouser are now selling duff chips!

I did try 47 and no dice. I'll try 100 and see what I get, but I don't hold out much hope. ... but that's one reason why I asked... at this point it can't just be a ram/cap thing?

I don't have any spare ferranti's to try either... I've got a couple of uLA81 on back order. No clue when they'll come.

[dr beep]

This game is the first to use executable code in upper memory, but that should not be the problem

[dr beep]

The lowres display is ok, problem is in the hiresdisplay.

[msknight]

The lowres display is ok, problem is in the hiresdisplay.

Correct. it's just the highres display that I can't get stable.

[msknight]

Incidentally, I use that game because it's quick to get in via tape.

Also, I appear to have a good clock. A little curved at the front and dipping below 0 on the drop, but hitting 5v at 3.25Mhz.

[msknight]

In case it matters for the price of fish, here's the clock as going in to the processor...

[dr beep]

I can tell you exactly what value must be read but not ATM.
Tonight earliest.

I WROTE THE GAME