Sinclair ZX80 / ZX81 / Z88 Forums

The ULA you have does generate the back porch signal.

In very simple terms, when the "X" command is used it means the ZXpand ROM is switched out and the ZXpand becomes just a 32k RAM pack with the ZX81 ROM now being in control.

The Zxpand uses the equivalent of the 622 (issue 2 ROM ) ROM according to Charlie, and relies on the Zeddy ROM for the CHR table. When switched out, in my case, Dark star is running on the 649 ROM (Issue 3. ) and works OK. In both cases constantly pressing break just returned both files to the K cur...

While testing the new driver I noticed that DSTAR crashes in 192 rows mode unless I add at least one NOP instruction. I'm not sure whether the crash is caused by a memory alignment problem or timing/sync issues, other programs run smoothly on EO. The Dark star in your sampler runs OK using UDG4ZXpa...

stefano wrote: ↑Thu Apr 04, 2024 11:06 pm Thank you. Could you test both the programs? They seem identical but one of the two includes a break keys detection

Break key didn't work on either of them.

stefano wrote: ↑Thu Apr 04, 2024 11:07 pm I'm also wondering what the 128 char mode is.

It allows you to use the inverse chr set.

Works with UDG4ZXpand using 64 chr mode, see picture, also a picture of it using 128 chr mode.

Will test this tonight and report back.

On real zeddy with UDG4ZXpand set for 64 mode Stefano's programs either crash or those that run have spurious dots and lines here and there, 128 mode makes it worse although the eagle one seems OK.

ARX is working well enough in Kmurta's Forth79 if that helps.

I have a UDG4ZXpand board and can test if needed.