Search found 379 matches

by RetroTechie
Sat Mar 24, 2018 4:52 pm
Forum: GAMES
Topic: Looking for a game
Replies: 6
Views: 1950

Re: Looking for a game

You might also want to check out "Damper", aka Colour Clash on the Spectrum. Download here:

www.zx81.nl/dload/software/d/
by RetroTechie
Fri Mar 16, 2018 1:42 am
Forum: GAMES
Topic: Copyrights for New Generation Software games (e.g. 3D Monster Maze)
Replies: 5
Views: 2361

Re: Copyrights for New Generation Software games (e.g. 3D Monster Maze)

This might be the worst advice ever, but: you could always just publish it and see what happens. Second that. If "just remove offending title if a copyright claim is received" works for you, then why not just go ahead. Ah yes, the -mostly theoretical- risk of legal problems / monetary damages etc. ...
by RetroTechie
Wed Mar 14, 2018 2:14 am
Forum: Development
Topic: do we still use UHF modulators ?
Replies: 17
Views: 4081

Re: do we still use UHF modulators ?

Looks like close to standard composite voltage levels the modulator wants, apart from a DC bias (say, series capacitor or so?). Sadly there's no info on typical input impedance for that modulator. :?: it does mean that broken zeddies which are not comp modded won’t be fixable with this ULA (..) Quit...
by RetroTechie
Sat Mar 10, 2018 1:30 am
Forum: Development
Topic: ZX81 ULA-in-a-CPLD
Replies: 233
Views: 64078

Re: ZX81 ULA-in-a-CPLD

@McKlaud and Andy: NICE!!! :) Especially Andy's 45-degree placement of the CPLD is likely how I'd have done it myself. The power consumption is roughly 250mA, but I have also got a 16KB SRAM chip on this board. I think I could go even lower if the 7805 were replaced with any decent DC-DC converter. ...
by RetroTechie
Wed May 31, 2017 12:56 am
Forum: WANTED
Topic: Looking for a 16K RAM extension for ZX81
Replies: 2
Views: 1835

Re: Looking for a 16K RAM extension for ZX81

Soldering iron at hand? ;)

ZX81 internal RAM expansion
by RetroTechie
Tue May 23, 2017 1:28 pm
Forum: Hardware
Topic: Resurrecting a ZX81 - Step by step help appreciated.
Replies: 26
Views: 5448

Re: Resurrecting a ZX81 - Step by step help appreciated.

TR2 acts like a buffer / 'enhancer' for the Z80 clock. So at the Z80 (pin 6) the clock signal should have much steeper edges (more like a block wave) than at the ULA output (pin 14). Seems to me that's not the case on several of the scope pics shown earlier. Which suggests that TR2 or surrounding co...
by RetroTechie
Thu May 04, 2017 12:39 am
Forum: Development
Topic: Lode Runner on the ZX81?
Replies: 54
Views: 12705

Re: Lode Runner on the ZX81?

It would be great to have this game on the Zeddy! Looking at Lode Runner levels & thinking about how to take advantage of typical layouts, you could do something like this: 1) Start with background + one or two different types of bricks only. That would encode as a series of (few bits + length in si...
by RetroTechie
Mon Apr 24, 2017 5:46 pm
Forum: ZX Spectrum Lounge
Topic: ZX Spectrum Next
Replies: 33
Views: 13155

Re: ZX Spectrum Next

Funded! :D

Btw pictures show a Xilinx XC6SLX9 (Spartan-6 family). Which is kind of a low-end FPGA. But should provide plenty space for other machine implementations that aren't too complex.
by RetroTechie
Fri Apr 21, 2017 9:44 am
Forum: Hardware
Topic: Putting a ZX81 onto a CPLD
Replies: 59
Views: 11041

Re: Putting a ZX81 onto a CPLD

There is no "one size fits all". For each application, determine: Whether you need 5V tolerance on I/O pins. 5V tolerant devices will need 3.3V power (or less), but I/O's can be hooked up directly. For non-5V tolerant devices, signals from a 5V system will need a voltage shifter (IC), series resisto...
by RetroTechie
Thu Apr 20, 2017 2:15 am
Forum: Sinclair Misc
Topic: Image on CRT's in Fast mode?
Replies: 12
Views: 3531

Re: Image on CRT's in Fast mode?

Thx everyone for your answers! :) So TV screen simply turns blank - sometimes black, gray(ish) or even white. And with the TV losing sync, prompting some TV's to go for a blue screen or display a message. Fwiw: that actually matches what I'm seeing with -my- composite modded ZX81's: a blank, white s...