Sinclair ZX80 / ZX81 / Z88 Forums

So I've got two partially failed ULAs ... or potentially to be generous, two ULA's that can't perform to the standard where WRX hires graphics will work, even if I was using the original 1k RAM. I think you have bunked why "some" ZX81s did not work with my hiresgames. We wanted to release a tape wi...

I made a simple testprogram out of a game.

After NEWLINE you will see 16 hires lines (well more, but also lines with zero)

First line 1 and 1
spaceline
Second 2 and 2
spaceline
Third 4 and 4
etc....

So you can see which bit are set by your computer.

Closer look at the picture

First thought:
The text is ok, but some bits are
somehow set.

The best thing you could have is a simple
display with just 1 (adjustable) value and see how that display appears.

msknight wrote: ↑Fri Mar 08, 2024 2:13 pm I'm not dissing the game, or your fine work in any way, shape or manner.

I don't take it in that way.

I can take a look what value from which address must be read/shown if that can help?

Hardware itself I can't help you with.

AFAIK Berzerk is pseudohires

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

I WROTE THE GAME

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

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

I think it interesting that this detail is conspicuously missing from the ZX81 User Manual, especially when it addresses which registers not to mess with. It doesn't seem like such a minor detail to me. The manual also doesn't mention the use of IX or A' which you can only use in a special way. IX ...

stroebeljc wrote: ↑Thu Mar 07, 2024 6:04 pm HL' is used by the FP calculator when machine code is launched using USR in BASIC. So you need to do what dr beep says and save-and-restore it.

Wow.... a 2015 thread revived!
Well if it helps anyone, why not!