Ok, if there is a delay in the start of the screen drawing then that means the interrupt is asserted earlier than on the spectrum models so I think a dedicated timex core is probably the way to go. That way you can fully capture other features not implemented in the spectrum next at the same time. For example, the internal bankswitching used for cartridges and the extended rom.I am a little surprised that the pal timex timing is different from the 48K. Timex had access to the Sinclair's ula design when making its scld. The first iteration was for the ntsc ts2068 so the display structure was changed for that and the counters used are documented in the ts2068 technical manual. But the scld was designed for both ntsc and pal and I assumed they would have just used Sinclair's counters for pal.