Turtlerock Forum

Specifically, I'm after a Z84C0004PSC. I'm troubleshooting a Lexicon PCM70 and I'm pretty sure the slave processor is kaput.

To the tech-types here... there are quite a few variations on the Z80, should I be sourcing this exact (vintage) version, or would a modern equivalent such as the Z84C0010PEG (or similar) be suitable?

Thanks!

What is the speed of the clock that is driving that processor? You will need a Z-80 that is rated for that speed or better. That's the most important number to consider, a 2 Meg Z80 won’t work on a circuit that is running a 4 Meg crystal for example.

Hey thanks Steve... yep looks like the slowest modern version is 6 Mhz so no problems there. The master and slave CPUs are fed by a 3.25 Mhz clock.

I actually emailed Zilog and got a response the next day -

"You can jump to the next speed which is 6/8/10 MHz version (Z84C00 06/08/10 PEG) version, as long as you’re compliant with the AC timing specifications."

So that sounds promising... although I must admit I don't know if the "AC timing" part of that advice is going to be an issue or not (I have no experience at all with CPU replacement).

I just now noticed that the modern version (Z84C0010PEG) is "ROMless"... not sure if that's what I want?

Anyway it's only a $10 part so will just drop one in and see (unless someone is going to tell me that things might explode).

Got the replacement, dropped it in, working PCM-70. Happy camper.