Sinclair ZX80 / ZX81 / Z88 Forums

I'm in need of a wee bit of assistance... ;) Have been locked out of my World of Spectrum account for a while. Forgot how it happened, iirc logging in didn't work any more after updating my e-mail address. Since I don't post there often & was busy with other things anyway, went into read-only mode f...

Agree on this one... :( I propose that users who only (or almost exclusively) use their account to post in the Sales section, be treated as spammers. And thus removed / blocked / banned / whatever. Above user would be a good example, just check this user's previous posts to see what I mean. Such use...

what ram would i be enabling ? A 32K*8 SRAM used in a simple internal 16K RAM mod? Say, enabled in 2000-9FFFh range. Or mirrored all over the 64K address space except the lower 8KB occupied by the ROM? (that would also be nice when using a 128K*8 SRAM to fill the entire 2000-FFFFh range with unique...

Great progress Andy! Looking good! :D oh my :geek: the link in the middle is mighty close to touching the case ... the easiest thing would be to fit a right angle header. (might have to bend it up slightly :? ) Personal opinion: put feature jumper(s) on a side end of the board. One pin solders to to...

Hi, anyone stumble across this already? A simple 8 bit micro, with an EPROM and SRAM chip as main memory, but using only TTL chips for the CPU. 8-) :ugeek: (74HCT actually, for those of you playing along at home ;) ). Homepage: https://gigatron.io/ Aussie electronics boffin Dave Jones just did a rev...

Hmm too hot to touch though? It seems to be giving out more then 5V closer to 7 Or measuring wrong - seen often when people (try to) check voltages. For 78xx regulators like the 7805 in the photo, seen from the front (printed) side, pins from left to right are input, GND, output. So you'd put your ...

Much preferable over a RAM pack: https://web.archive.org/web/20150905141235/http://bitcycle.org/retro/zx81/internal_RAM/ Cheap, fairly easy, no RAM pack wobble, edge connector remains free for other add-ons like sound card, flash card storage etc. The original 16K RAM packs were poorly designed & an...

74HC -> 74LS: no problem, unless you're driving many LS inputs at once. In that case check datasheets / calculate load currents etc. 74LS -> 74HC: often works fine. In general, just check properties of IC where a signal comes from (and check datasheet of the HC part where it goes to). Better: add a ...

You must remember for port $FE to work correctly you use open collector drivers only.. DO NOT DRIVE DATA LINES HIGH. So you see the ula can if it's wants drive a data line low , or an external device can drive it low. High is created by the pull-up when nothing drive it low. Commonly known as " wir...

At least for the TS1000, RF (TV) output is on V HF channel 2 or 3. Versus U HF channel 36 on a regular (UK) ZX81. Also note the channel select switch on the bottom, which is not present on a UK ZX81. And the somewhat-conductive silvery paint + metal strip inside the case on US models (for EMI shield...