Sinclair ZX80 / ZX81 / Z88 Forums

Yes, I'm at the final stages of the ULA replacement. everything is in place except the YUV output. (currently using RGB as the output for testing, hooked up to an off the shelf composite generator with an AD724). That said, there must be an easier less complex way to do this, as looking at the exist...

Thanks. So the two solutions I can see are: 1) Use 3 channel summing op amps to generate each of the YUV signals, using resistors to get the correct coefficients for RGB.. 2) inside the ULA CPLD, identify the 8 colours with brightness.. and then output to a DAC, and generate the YUV from the DAC.. t...

Thanks. I have searched everywhere for this. The arithmetic formulas are straightforward, but implementing this when RGB is digital is tricky.

Y can be got from an AD724, but then the problem is U and V...

Hi, Does anyone have any insight on how to convert RGB (which is three digital CMOS signals to Y'UV). Y'UV is what is output from the ULA. I am at the final stages of my project and need to convert RGB to Y'UV'. A formula if given in the Chris Smith Book, on the ULA and I assume some sort of resisto...

great. thanks for the help. I saw on thread that whywait improved performance by 10% and noWait by 30% which was a little confusing! THanks again.

Any recommended software for measuring / benchmarkins ZX81 speeds?

Andy

Thanks Mark,

Being a newbie (or maybe idiot), this is not the whyWAIT(?) mod, this is the noWAIT mod? Is there any benchmarking tools that can be used to see if it is working or the impact?

Thanks so much.

Andy

Hi, I have read of the 'noWAIT' mod on the ZX81. Does anyone have any more details on this and how it is implemented? I cant find any specifics on it? Also, is there any recommended benchmarking and test software for the ZX81? speed tests, timing tests etc? New to the ZX81 world, coming from the ZX ...