Sinclair ZX80 / ZX81 / Z88 Forums

Agreed, Mark, I think we can consider this one answered and closed.

The centre for computing history has an interesting entry re the ZX80 and John Grant of Nine Tiles the author of the ZX80 ROM. Quote. "The 8K Rom was withdrawn in September 1980 to reprogram it to add printer support among other things. Before finally being incorporated in to the ZX81 ROM." My take ...

I would tend to agree, why re-invent the wheel?

There is an upgrade ROM (assumed genuine ) up for sale on ebay and if it is the real thing then it's just a 550 which I've always thought was the one supplied by Sinclair.

Click picture to enlarge.

I understand and already knew about the overlay keyboard, but if you read the statement it implies that different code was used in the ZX80 "upgrade" ROM chip and this code was not the same code as used in a standard ZX81 550,622 or 649 ROM.

Hope that's clearer.

Whilst browsing some ZX80 YouTube videos I came across this statement .... Quote. "i wish people would get it right, they did not put 8k zx81 roms in them on the up grade, they put a special 8k zx80 romset in, it had all the extra functions and the keyboard was correct, putting a zx81 rom in a zx80 ...

This is an old topic, pictures can be found in this thread, zip file 5th post.

https://www.sinclairzxworld.com/viewtop ... dac358f8d7

Although the picture is quite blurred It looks like the solder coating has worn down to the copper tracks underneath in places making the edge connection unreliable, I would do as stroebeljc advises and re-coat the edge connector with solder.

Your screenshot seems not to match Stefano's.

I have all issues of ZXpand including a recent prototype and like Paul have no problem with wobble whatsoever so yeah perhaps dirty or worn/uneven plating on edge connector.

yes, 16K or larger capacity RAM packs for the ZX81 should work fine with a TS1000. Also 2K, 3K and 4K made for ZX80 work fine on a ZX81 or TS1000 I Thought a track had to be cut in these ZX80 RAM packs for them to work rather than plug and play as your post suggests, apologies if I've misunderstood...