Search found 1610 matches

by Andy Rea
Thu Jan 25, 2024 8:47 pm
Forum: Development
Topic: Oh no! Not another ULA.
Replies: 79
Views: 106589

Re: Oh no! Not another ULA.

Quick update for what it's worth...

Crap happens... My personal circumstance has changed somewhat.

Project on hold until further notice.

Regards Andy
by Andy Rea
Sat Oct 28, 2023 2:33 pm
Forum: WANTED
Topic: UDG 4 ZXpand
Replies: 4
Views: 8973

Re: UDG 4 ZXpand

Don't hold your breath as nothing may come of it.. but currently in talks with a third party who is interested in producing some UDG4ZxPand boards.

Andy
by Andy Rea
Fri Oct 20, 2023 9:40 pm
Forum: SALES
Topic: Swetland ZX81+38 Mechanical Keyboard PCB only - 3 available
Replies: 40
Views: 27033

Re: Swetland ZX81+38 Mechanical Keyboard PCB only - 3 available

Long time posting in this thread, I have purchased a set of stickers as mentioned in This Thread I'm going to try the non ZX81 stickers on some contoured keycaps from an old keyboard and see how they look. if they are alright i'll use the zx81 stickers, otherwise i'll use the zx81 stickers on the fl...
by Andy Rea
Tue Oct 10, 2023 9:47 pm
Forum: Development
Topic: Oh no! Not another ULA.
Replies: 79
Views: 106589

Re: Oh no! Not another ULA.

Paul wrote: Fri Oct 06, 2023 8:30 am Maybe inside the CPLD?
yes this probably, heck if your already soldering half a dozen extra wires for additional features, changing your rom to a faster one, and possibly your ram ( whoever is still using internal 1 or 2K ) then heck a few more wires ain't gonna hurt.

Andy
by Andy Rea
Thu Oct 05, 2023 9:54 pm
Forum: Development
Topic: Oh no! Not another ULA.
Replies: 79
Views: 106589

Re: Oh no! Not another ULA.

Paul wrote: Thu Oct 05, 2023 6:16 am My guess is he wants to short R28
Remove completly.
by Andy Rea
Thu Oct 05, 2023 9:53 pm
Forum: Development
Topic: Oh no! Not another ULA.
Replies: 79
Views: 106589

Re: Oh no! Not another ULA.

You mean either side of R28… One side is connected to the ULA. The other side is connected to the edge-connector and (on a standard machine) to the ROM. But I presume on a modified machine, the output of the OR gate will drive the ROM instead. Because the OR gate has one input directly connected to...
by Andy Rea
Wed Oct 04, 2023 4:13 pm
Forum: Development
Topic: Oh no! Not another ULA.
Replies: 79
Views: 106589

Re: Oh no! Not another ULA.

OK I think I was right the first time lol

if I take the romcs at the edge connector ( with a pull down resistor) to one input of an OR gate and the other input from the ula generated ROMCS and the output directly to the internal ROM.

that will work right?
by Andy Rea
Tue Oct 03, 2023 6:11 pm
Forum: Development
Topic: Oh no! Not another ULA.
Replies: 79
Views: 106589

Re: Oh no! Not another ULA.

A question for the technical minded... does anybody know of any external device that uses the ROMCS signal at the edge connector in any way other than to override the internal ROM? reason I ask, with fasr enough cpu, ram and rom in the zx81 13Mhz is possible. ( without zxpand connected ) with zxpand...
by Andy Rea
Tue Sep 26, 2023 6:36 pm
Forum: Development
Topic: Oh no! Not another ULA.
Replies: 79
Views: 106589

Re: Oh no! Not another ULA.

@Andy You say 70ns ROM for Big Bang, I assume ,after seeing your video that, this is a custom chip? its just a at28hc64b-70su eeprom but SOIC on a SOIC to DIP adapter board. a regular DIP eeprom of the same speed should work.. slower chips should work but because all that stupid resistors bridges t...
by Andy Rea
Tue Sep 26, 2023 6:30 pm
Forum: Development
Topic: Oh no! Not another ULA.
Replies: 79
Views: 106589

Re: Oh no! Not another ULA.

1024MAK wrote: Mon Sep 25, 2023 11:54 pm Would now be a bad time to suggest 6X :lol:

Mark
I've got one of those.... the 20Mhz Zeddy... normal speed is slightly fast at 3.33Mhz

It is anything but a standard zeddy, ask Moggy...