Hi 1024MAK
It's a plastic OTP ROM (Intel P27256) I think? (Could be a mask ROM I guess).
I've attached a pic.
Cheers again,
KbJ
ZX Spectrum 128k toastrack horizontal bars at power up
Re: ZX Spectrum 128k toastrack horizontal bars at power up
Folks are like binary, one or the other..
- 1024MAK
- Posts: 5118
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: ZX Spectrum 128k toastrack horizontal bars at power up
Yeah, that’s definitely a OTP EPROM. Intel refers to it as a ‘production’ or ‘plastic’ part in their datasheet (attached).
It’s likely it’s starting to suffer from the memory contents degrading.
You could try reprogramming it. But that will only work if you use exactly the same file / data that it was originally programmed with. And it is possible to set your programmer to ignore the fact that it’s not ‘blank’. And your programmer either tries programming each memory location before checking it ‘programmed’ okay rather than reading and then deciding if each memory location needs programming. Or you can force it to program each memory location regardless. In other words, it needs a ‘dumb’ (slow) programming algorithm not a fast, intelligent or smart programming algorithm.
Then if successful. Try it in the machine again.
But obviously only do this if you find this kind of thing fun
Mark
It’s likely it’s starting to suffer from the memory contents degrading.
You could try reprogramming it. But that will only work if you use exactly the same file / data that it was originally programmed with. And it is possible to set your programmer to ignore the fact that it’s not ‘blank’. And your programmer either tries programming each memory location before checking it ‘programmed’ okay rather than reading and then deciding if each memory location needs programming. Or you can force it to program each memory location regardless. In other words, it needs a ‘dumb’ (slow) programming algorithm not a fast, intelligent or smart programming algorithm.
Then if successful. Try it in the machine again.
But obviously only do this if you find this kind of thing fun
Mark
- Attachments
-
- Intel 27256 DSAP0039393.pdf
- Intel 27256 datasheet
- (422.46 KiB) Downloaded 97 times
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.