Search found 207 matches

by Brane2
Wed Jul 28, 2021 10:18 pm
Forum: Hardware
Topic: Unreliable microdrives
Replies: 8
Views: 186

Re: Unreliable microdrives

My original QL was a JM and had a faulty drive 2. I had it replaced under warranty with a JS, lucky me. That one served me well for numerous years with no mdv problems at all. Come on. Every tape degrades with use. You had NEVER seen mdv fail on you ? How often and how much had you used those thing...
by Brane2
Wed Jul 28, 2021 8:59 pm
Forum: Hardware
Topic: driving magnetic heads ( floppy, auudio etc)...
Replies: 0
Views: 43

driving magnetic heads ( floppy, auudio etc)...

If one would to attempt to recreate media of the time to see where the theoretical maximum is and what part of that could be actually used: WHere would find info on driving floppy drive head ? How about realistic characteristics of audio head ? Could audio head be used without separate erasing head,...
by Brane2
Wed Jul 28, 2021 8:48 pm
Forum: Hardware
Topic: Unreliable microdrives
Replies: 8
Views: 186

Re: Unreliable microdrives

I've used them exclusively for quite some time.
They were sh*tty even by the standards of the day.

That being said, it would be interesting to reimplement the PCB to see what it could have been, had it be done decently.

AFAIK, they don't use both tracks - both carry the same signal etc.
by Brane2
Wed Jul 28, 2021 5:20 pm
Forum: Hardware
Topic: ULA replacement - could it work in 16-bit mode ?
Replies: 4
Views: 180

Re: ULA replacement - could it work in 16-bit mode ?

[EDIT]: deleted- misquoted doublepost.
by Brane2
Wed Jul 28, 2021 5:00 pm
Forum: Hardware
Topic: ULA replacement - could it work in 16-bit mode ?
Replies: 4
Views: 180

Re: ULA replacement - could it work in 16-bit mode ?

Having looked at the ZX8301 timings a while ago, I was more than a bit perplexed why it did not use interlieve bank access since it actually always has two 64k banks at it's disposal. It also has two CAS lines. Same here. Also, why didn't he simply package two ULAs in something bigger ( like PLCC68...
by Brane2
Wed Jul 28, 2021 3:49 pm
Forum: Hardware
Topic: zx8301 replacement
Replies: 17
Views: 901

Re: zx8301 replacement

And use FPGAs fast ISP configuration FLASH in x4 mode as QL's ROM. These are paged devices so one would need to implement cache or get painfully slow even in x4 mode. It's much easier to shadow the ROM in RAM, and in that case, primitive 1x SPI is more than fast enough. You don't even notice. I hav...
by Brane2
Tue Jul 27, 2021 10:20 pm
Forum: Hardware
Topic: zx8301 replacement
Replies: 17
Views: 901

Re: zx8301 replacement

BTW, if Sinclair was today using FPGAs, im 100.00% sure he would f**k around with reimplementing 35yr old concepts with modern chips. His team would be circling around all players, seeking insider info and doing crazy stuff with THIS tech. If they went with FPGAs, you can be sure they'd be deeply in...
by Brane2
Tue Jul 27, 2021 10:11 pm
Forum: Hardware
Topic: zx8301 replacement
Replies: 17
Views: 901

Re: zx8301 replacement

So it would IMHO make sense to do something that would also serve as pure ULA replacement and keep the rest of the machine physically close to "real deal". Sure, but it costs a lot more time than re-using the existing FPGA logic. Far beyond what I would consider. And with the disadvantage...
by Brane2
Tue Jul 27, 2021 12:03 am
Forum: Hardware
Topic: ULA replacement - could it work in 16-bit mode ?
Replies: 4
Views: 180

ULA replacement - could it work in 16-bit mode ?

I've just took a peek at old 41256 dram datasheet. Setup times are narrow enough to enable intelieveing 2 8-bit banks, even on word level. Which means that one could use existing circuitry on PCB to transfer data between CPU socket VIDEO DRAM and ULA1 socket 16-bits at the time, provided that they a...
by Brane2
Mon Jul 26, 2021 6:09 pm
Forum: Hardware
Topic: zx8301 replacement
Replies: 17
Views: 901

Re: zx8301 replacement

Agree 8301 replacements are becoming increasingly rare, and in the long run, it could make sense to think about replacements. The 8301 is, however, much less well (rather not at all) documented as the Spectrum chips. Documentation is only an issue, if the exact timings have to be replicated. The qu...