Sinclair ZX80 / ZX81 / Z88 Forums

I have an ZXpand+ and having trouble with wobble all the time. I ask the family not to breath near the table when I use the ZXpand+. Stange we can have so different experiences. Since I touched up each tab on the edge connector with a thin bead of solder, I've had no wobble problems, even with the ...

I did a bit more work on this, but still have some white bars at the top and bottom on the 60Hz build. The problem is that eliminating the white bars slows gameplay too much. So, here is where I've ended up.
50Hz 60Hz

Here is a 60Hz version for those, like me, afflicted with NTSC, including source code (compiled using TASM with NTSC defined). I'm stuck with a white line at the top because of how little processing time is left over for gameplay. Any ideas on how to remove it, if possible?

I love your suggestions, XavSnap.
You're such a trickster!

Hi, In BASIC, after a FAST/SLOW process, an unsightly scrolling can occur when exiting the FAST mode. To avoid this dropout of the screen frame, just add a PAUSE before the SLOW commande: 10 FAST (... your code..) 1000 PAUSE 0 1010 SLOW Have fun. ...and don't forget to add this line if running on f...

Sort of like the calculators of the day.

Internally accurate down to 1/(2^32) ~= 0.0000000002328306437. So, yes, 9 to 10 digits. 32/log2(10)=9.63, to be more precise.

The ZX81 is only capable of precision to 8 digits. Thus, the rounding.

The ZX81 "PAUSE bug" Explained After trying to understand the exact nature of the ZX81 ROM PAUSE bug, I decided to write down the observed behavior for anyone interested. I'm sure there are details that others on this forum could add or correct, and I hope this thread can pull them out to be a one-...

A few final tweaks before moving on to something else.
The project is also available on GitHub.