Sinclair ZX80 / ZX81 / Z88 Forums

McKlaud wrote:A10 line is connected via L2 (link) to the new memory chip.

Yes, you had to connect the L2 bridge.

A different method (cutting tracks on the PCB) is shown here (the advantage being you can use plug in a new RAM chip without having to mess about with wires on some of the pins).
This site shows details of all the extra connections including the link wire.

Mark

Did anyone take a copy of Dave C's blog post for this upgrade? It looks like Dave's taken down his blog due to ongoing requests - which leaves me in the lurch as I was going to do this upgrade at the weekend now the Ram chip has arrived.

I know there's some more "permanent" versions available but I really don't want to cut any tracks; it's very unlikely that it'd ever be reversed anyway, but I'd prefer an option, just in case of problems.

Trevor

It’s slow to load, but there is an archived copy here.

Mark

Thanks very much Mark - much appreciated.

I've now got a PDF version stored so hopefully it'll all be good.

Once again - thanks

Trevor

If you have any questions about this or any other 16K internal RAM modification, please ask.

Mark

Not the greatest start today - thought I'd make sure the machine was working before upgrading, only to find the 20+ year old telly I'd recently bought for it's analog tuning doesn't actually have an aerial socket. So - I'm going to take the zx8-ccb route initially ( I have one) - just to make sure things work then I'll do the upgrade. A minor setback - I just ran out of time due to other family "stuff".

I was able to successfully use a Toshiba TC55257 which, consulting its datasheet, was sold as an equivalent to the various 62256 chips commonly suggested for this mod. I found it by simply Googling "32KB SRAM DIP-28" I think. There's one left for £1.80 if you're quick!
https://www.ebay.co.uk/itm/143432785940