Search found 363 matches

by RetroTechie
Thu May 04, 2017 12:39 am
Forum: Development
Topic: Lode Runner on the ZX81?
Replies: 54
Views: 6975

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: 31
Views: 7807

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: 6626

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: 1802

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...
by RetroTechie
Wed Apr 19, 2017 5:01 am
Forum: Sinclair Misc
Topic: Image on CRT's in Fast mode?
Replies: 12
Views: 1802

Image on CRT's in Fast mode?

Just a quick question: If you take an unmodified ZX81 (read: video output via VHF/UHF modulator), a good old CRT, and the ZX81 enters Fast mode, what is seen on the screen? I keep 'remembering' :? that in this case the CRT would output 'snow' (random pixels), same as between TV stations when searchi...
by RetroTechie
Fri Apr 14, 2017 12:42 am
Forum: Hardware
Topic: Problems with my ZX81s
Replies: 24
Views: 2506

Re: Problems with my ZX81s

For the edge connector, try using clean paper (no ink, fingerprints or 'glossy' layer etc). This acts as a very fine / very mild sandpaper. With no solvent of any kind. 8-) Regular printer paper works well. At first you'll see the paper catch black dirt, simply continue with another piece of clean p...
by RetroTechie
Wed Apr 12, 2017 7:19 pm
Forum: Hardware
Topic: Z80 CPU compatibility
Replies: 4
Views: 862

Re: Z80 CPU compatibility

Just get a CMOS version (Z84 C 00xx), it'll run cooler. I've even had East-German Z80 clones (UB880 = 2.5 MHz version) working in a ZX81. Which isn't surprising since a 2.5 -> 3.25 MHz overclock is quite moderate by Z80 standards. 8-) Working fine in ZX81 but problems with peripherals attached = pro...
by RetroTechie
Mon Apr 10, 2017 5:43 pm
Forum: Hardware
Topic: ZX81 Chip Pin-outs
Replies: 22
Views: 7288

Re: ZX81 Chip Pin-outs

Just checked the above pdf. For some reason cbmbsw included the pinout of a 2K*8 PSEUDO -static RAM (a dynamic RAM with static RAM like pinout), which is USELESS . The only ZX81's that came from factory with 2K installed were TS1000's, and the RAM chips used there are standard pinout 2K*8 static (no...
by RetroTechie
Mon Apr 10, 2017 5:02 pm
Forum: Hardware
Topic: ZX81 Chip Pin-outs
Replies: 22
Views: 7288

Re: ZX81 Chip Pin-outs

Just go with the ZX81 schematic, and datasheet for the exact RAM IC's that are fitted. These are either 2 pieces 1K*4 bit RAMs, or a single 1K*8 bit RAM (or 2K*8 in the case of a US-sold TS1000, with LK1 wire link in LK2 position). All those RAM chips are static RAMs and have standard pinout. So unl...
by RetroTechie
Wed Mar 08, 2017 12:40 am
Forum: Hardware
Topic: ZX81 / Timex 1000 tape loading
Replies: 29
Views: 3241

Re: ZX81 / Timex 1000 tape loading

Filename is useful when there are multiple programs on a tape. Or a program consisting of several parts (somehow). But... nothing that couldn't be handled using a tape counter. If not using an MP3 player... :)

Outside that, LOAD "" works just as well.