Search found 121 matches

by Erm
Sun Dec 15, 2019 6:27 pm
Forum: Hardware
Topic: Earliest known ZX81?
Replies: 5
Views: 455

Earliest known ZX81?

Mentioned in another recent topic, but I thought I'd share it here so that people can find and add details of early ZX81's. This one is very early, so I have bragging rights for now ;). (date codes are year followed by week number, for those that aren't aware) Modulator: 8106 ULA chip: 8102 (type 15...
by Erm
Sun Dec 15, 2019 1:08 pm
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 25
Views: 1367

Re: vLA81 ULA and 16/32K internal RAM

Yes, I suppose it's harder to swap out a RAM chip if it has soldered attachments, but the way I see it, it's not like they are likely to see so much use that the new RAM will ever fail and even if it does, if you use a modded ZX81 in 2019 then it's likely a bit of soldering won't be all that dauntin...
by Erm
Sun Dec 15, 2019 12:59 pm
Forum: Hardware
Topic: I got a ZX80!
Replies: 10
Views: 860

Re: I got a ZX80!

You should be ok getting the ROM from MCG - they burn them to order. Best hurry though - they tend to have some time off over xmas!!! Soft spongy feet and ZX80 PSU? Always good signs of an early one. I think the earliest ULA I have had is 8105 so I’m very jealous of that! No real hurry, it can wait...
by Erm
Sun Dec 15, 2019 12:11 pm
Forum: Hardware
Topic: I got a ZX80!
Replies: 10
Views: 860

Re: I got a ZX80!

Thanks, I'll see if I can get one the same type from Mutant Caterpillar that will involve no soldering to the board. As an aside, the other week I got a very, very early ZX81 (8106 Modulator, 8102 ULA, 8028 RAM) which actually had a ZX80 PSU with it, the same ZX80 type cassette and RF cables and sli...
by Erm
Sun Dec 15, 2019 12:06 pm
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 25
Views: 1367

Re: vLA81 ULA and 16/32K internal RAM

I always prefer not to cut anything. Just personal preference, I'm trying to go for the record of having the most pins bent out on a ZX81 ;)
by Erm
Sat Dec 14, 2019 9:27 pm
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 25
Views: 1367

Re: vLA81 ULA and 16/32K internal RAM

* I assume L1 needs to be changed to L2? * With the mod as shown the zeddy has 32K of RAM? * Does that leave it in a state where most / all commercial software will still work? (Concerned that games that expect things to be in a specific RAM location will be unaffected) * Does it support the common...
by Erm
Sat Dec 14, 2019 8:12 pm
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 25
Views: 1367

Re: vLA81 ULA and 16/32K internal RAM

There are a few places you can get the A11-14 from (also depends on if Iss1 or Iss3 and how convenient/neat you want to be). Here's an example, the wires from the RAM go through the board and connect with pins 1 - 4 of the Z80: 20190917_235642_resized_1.jpg There are also convenient places on the Is...
by Erm
Sat Dec 14, 2019 8:08 pm
Forum: Hardware
Topic: I got a ZX80!
Replies: 10
Views: 860

Re: I got a ZX80!

I have a programmer. But to fit a newer one on a standard eprom would need an adapter on the board and that wouldn't fit at all (and I don't want to make any changes at all to the actual board, even soldering). I thought a ROM-el would fit, but it's a gnat's whisker too tall. I remember seeing an or...
by Erm
Sat Dec 14, 2019 6:47 pm
Forum: Hardware
Topic: I got a ZX80!
Replies: 10
Views: 860

I got a ZX80!

Got this today. And it was a bargain if I do say so! I discovered that it has a vigin exp port too, never scratched by a RAM pack, much to my delight. It has a few marks and a little rip in a lower corner. It came with a ZX81 ROM and ZX81 keyboard overlay. I removed the overlay and as there's not mu...
by Erm
Sat Dec 14, 2019 6:41 pm
Forum: Hardware
Topic: vLA81 ULA and 16/32K internal RAM
Replies: 25
Views: 1367

Re: vLA81 ULA and 16/32K internal RAM

I've done a few of these (and have done a lot of fiddling with various configurations and written a lot of emails bothering Mr Ingley with silly questions) and there is no need to cut any tracks, just bend out 4 pins (1,2,23,26) of the 32k RAM chip and connect to address lines A11 to A14. Note that ...