Sinclair ZX80 / ZX81 / Z88 Forums

I did a simple experiment with EighyOne, the h4th roms stop working if you choose a memory size > than 16k and enable the m1not circuit. I tried unsuccesfully to patch the ROM and move all the system variables under 32768, but I did not succeed fully nor the partial results changed the EO behavior. ...

I see, I'll peep starting from the beginning, but I suppose a defect on the video loop would result on an almost immediate crash. The video driver gets the current value from locations FC80h and FC82h and jumps in it. Just to be sure let me ask again: is the data memory access managed in the same wa...

The strange thing is that this same ROM seems to have been used also by the Delhez`a emulator (xt2). Are we sure it is the ROM being faulty? A faster load/save routine could have been inserted by purpose.

I had a deeper look in the 4th roms. First of all, they're very similar. The only differences are in the video loop and in the copyright message. This permits us to understand that this video: http://www.youtube.com/watch?v=J-f26z8Vqo4 is running in PAL mode.. if you look at it carefully you'll noti...

You're absolutely right ! Apologies for having increased the entropy :/ I just discovered that EightyOne had and probably still has a small timing bug (1T difference probably raising from the Z80 emulation engine) which could have been a good reason to patch the original ROM. I'm curious now, prehap...

"The other issue of the sloping display is the kind that gives my nightmares... I have a 1-T error in my z80 core somewhere that Azmic has just discovered. MikeW Uh, wow.. this explains few things on the difficulties I was having to get a stable display with some z88dk program, expecially when work...

For those who may be interested.. the default text mode on z88dk is "case sensitive", which means it uses the normal characters for the lowercase characters and the inverted mode for the uppercase stuff. This came after a Siggi's suggestion trying to squeeze the maximum from the console and being ab...

While you're on it, could you try the 'vanilla' version on the real hardware and confirm the video picture is stable on a tv ?

Yes, also the europe/america diode trick is great !

About the ROMs.. I don't think they're tweaked, my impression is that h4th was for a 60hz raster only while aszmic was for 50hz only.
At least it's the way EightyOne behaves.

I like Zombie Terror.. looks quite simple but it is very well presented.