desUBIKado wrote:I have tried your core a little and I've saw a visual issue with the first lines of the screen
There's a 2 clock cycle skew in the HSync counter at the first line, which I don't know if it's a problem with the T80, my ZX81 implementation, or it's just there with the original hardware, too. For example, it is hardly noticeable on my TV, but with scandoubling it's very obvious.
Also there are conflicting informations on the net when the HSync counter should be synchronized, Grant Searle's site says it's synced to INTACK, but other places says it's synced to VSync. So if somebody has more information about it, please share. Currently it's synced to INTACK.