9 ms·

Building a new ZX Spectrum from all new parts

198 points by mariuz 3y ago

tyingq 3y ago
Apparently the hardest part used to be the ULA chip, but now there are CPLD based replacements. This project used this one from Charlie Ingley: https://www.tindie.com/products/charlieingley/vla82-spectrum-48k-ula-replacement/ https://www.tindie.com/products/charlieingley/vla82-spectrum... It uses a Xilinx XC95144 CPLD to emulate the ULA: https://docs.xilinx.com/v/u/en-US/ds067 https://docs.xilinx.com/v/u/en-US/ds067
- nickt 3y ago
  That’s pretty neat, the ULA is just a gate array after all. [Edit] I forgot to mention I have speccy and ZX81 ULAs from Charlie and they are top notch and have been working flawlessly, and especially in the case of the ZX81, better than the original. Chris Smiths’ book, “The ZX Spectrum ULA: How to design a microcomputer”, is an excellent read if you like to imagine yourself as a hardware guy back in the 80’s. http://www.zxdesign.info/book/ http://www.zxdesign.info/book/
- Pixelbrick 3y ago
  There's also the superfo harlequin that disintegrates the ULA into 74 series logic: https://www.bytedelight.com/?product_cat=harlequin128 https://www.bytedelight.com/?product_cat=harlequin128 I'm currently building the 48k version
- wlesieutre 3y ago
  For anyone else who's unfamiliar, that's a "Complex programmable logic device" https://en.wikipedia.org/wiki/Complex_programmable_logic_device https://en.wikipedia.org/wiki/Complex_programmable_logic_dev... > A complex programmable logic device (CPLD) is a programmable logic device with complexity between that of PALs and FPGAs, and architectural features of both. The main building block of the CPLD is a macrocell, which contains logic implementing disjunctive normal form expressions and more specialized logic operations.
pthreads 3y ago
Loved it! I couldn't find any info on the case and keyboard though. Did he just reuse an old one? They did look to be in mint condition. No mention of those in the video either (or maybe I just missed it as I was skipping over some sections).
- rzzzt 3y ago
  Replacements do exist both for the membrane as well as the rubber keys on top. The author lists it in the parts page under "Misc": https://www.lostretrotapes.com/zx-spectrum-issue-3b-parts-list/ https://www.lostretrotapes.com/zx-spectrum-issue-3b-parts-li...
  - pthreads 3y ago
    Thank you. I must have scrolled past it the first time around.
deleted 3y ago
[deleted]
glimshe 3y ago
It's somewhat humorous that the most expensive part is the manual! And no wonder electronics nowadays stopped including comprehensive manuals like the Spectrum's in their aggressive cost cutting.
- mchannon 3y ago
  Making a second, third, or fourth set of manuals would have obtained substantial economies of scale whether in the 20th or 21st centuries. There was a time where PDF didn’t exist, there were no tools to create, let alone view or print manuals. Even when these became widespread, a number of troglodytes would get bent out of shape if their new appliance didn’t come with a (preferably bound!) paper manual. Most of these folks have either passed on or begrudgingly assimilated.
  - SoftTalker 3y ago
    I'm kind of in that camp with cars. The last car I bought didn't come with an owner's manual. I've "begrudgingly" accepted that a PDF copy on my phone is for most practical purposes just as good, but I still prefer the paper. It's just easier to read, thumb through, or check the index and find what I'm looking for than doing the same on a small touch screen.
    - jaredhallen 3y ago
      Agreed. I buy real factory service manuals for any car I plan to keep for any length of time. They go for about $100 on eBay and are worth every penny.
- mananaysiempre 3y ago
  For small-run offset printing (as opposed to laser-printer-quality stuff you get from print-on-demand shops, including PoD reissues of old titles the big academic publishers sell under the guise of new copies), the books themselves are basically free compared to the plates. A bookshop owner who also worked in printing once told me it was in the order of $1M for the plates for a 300-page book, and then negligible costs for the actual books until you get past at least tens of thousands of copies. So printing one manual or a hundred of them is a very different proposition from a normal-sized run of like 50k of them.
TillE 3y ago
I love projects like this. It's even simpler to just homebrew your own 8-bit computer / game console from widely available parts, and a great way to learn about and really understand how computers work. Computers have become far more complex, but the broad fundamentals are basically unchanged since the 1970s.
- wkjagt 3y ago
  I did Ben Eater's 6502 kit and expanded on it a lot. You're right, it really gets you to appreciate how computers really work, in a much simplified way of course, compared even to for example the first IBM computer. Implementing something like a FAT file system for example also really makes you appreciate the deeper concepts of how an OS works. I only did a very simple FAT implementation, without subdirectories, but even with that, terms like FAT and sector became very concrete things instead of vague concepts.
  - eek2121 3y ago
    Ben Eater is awesome. I knew most of the stuff for x86, but revisiting all the things on a breadboard for 6502 and peripherals? AWESOME.Note of the snobbish: you can even build your own graphics card.
urbandw311er 3y ago
I loved this. Did he shrink wrap it only to then immediately rip it open?
vsviridov 3y ago
So, a 100 pounds in the 80s is almost 500 pounds today, according to the UK inflation calculator. So his build total cost is below that... Arguably 100£ was the retail price, not costs, but still
- xyzzy3000 3y ago
  For those wanting a link: https://www.bankofengland.co.uk/monetary-policy/inflation/inflation-calculator https://www.bankofengland.co.uk/monetary-policy/inflation/in...
azurefan 3y ago
Pretty cool post. I’ve been playing spectrum games recently http://torinak.com/qaop/games http://torinak.com/qaop/games
ConanRus 3y ago
Back in the end of 80s - 90s in the USSR/Russia were were lots of ZX Spectrum variants, and none of them had the ULA. They all were engineered to use the most popular and easy to obtain components. So i believe you still can build one for cheap. This one was one of the most popular variants https://en.wikipedia.org/wiki/Pentagon_(computer) https://en.wikipedia.org/wiki/Pentagon_(computer)
lovegrenoble 3y ago
You brought back my childhood memories, thank you!
Wajeez 3y ago
If we were to upgrade that hardware design to say Speccy 4 or 2023 for that matter... What CPU, GPU, and OS would we use?

198 points by mariuz 3y ago

Apparently the hardest part used to be the ULA chip, but now there are CPLD based replacements. This project used this one from Charlie Ingley: https://www.tindie.com/products/charlieingley/vla82-spectrum-48k-ula-replacement/ https://www.tindie.com/products/charlieingley/vla82-spectrum... It uses a Xilinx XC95144 CPLD to emulate the ULA: https://docs.xilinx.com/v/u/en-US/ds067 https://docs.xilinx.com/v/u/en-US/ds067

nickt 3y ago
That’s pretty neat, the ULA is just a gate array after all. [Edit] I forgot to mention I have speccy and ZX81 ULAs from Charlie and they are top notch and have been working flawlessly, and especially in the case of the ZX81, better than the original. Chris Smiths’ book, “The ZX Spectrum ULA: How to design a microcomputer”, is an excellent read if you like to imagine yourself as a hardware guy back in the 80’s. http://www.zxdesign.info/book/ http://www.zxdesign.info/book/
Pixelbrick 3y ago
There's also the superfo harlequin that disintegrates the ULA into 74 series logic: https://www.bytedelight.com/?product_cat=harlequin128 https://www.bytedelight.com/?product_cat=harlequin128 I'm currently building the 48k version
wlesieutre 3y ago
For anyone else who's unfamiliar, that's a "Complex programmable logic device" https://en.wikipedia.org/wiki/Complex_programmable_logic_device https://en.wikipedia.org/wiki/Complex_programmable_logic_dev... > A complex programmable logic device (CPLD) is a programmable logic device with complexity between that of PALs and FPGAs, and architectural features of both. The main building block of the CPLD is a macrocell, which contains logic implementing disjunctive normal form expressions and more specialized logic operations.

pthreads 3y ago

Loved it! I couldn't find any info on the case and keyboard though. Did he just reuse an old one? They did look to be in mint condition. No mention of those in the video either (or maybe I just missed it as I was skipping over some sections).

rzzzt 3y ago
Replacements do exist both for the membrane as well as the rubber keys on top. The author lists it in the parts page under "Misc": https://www.lostretrotapes.com/zx-spectrum-issue-3b-parts-list/ https://www.lostretrotapes.com/zx-spectrum-issue-3b-parts-li...
- pthreads 3y ago
  Thank you. I must have scrolled past it the first time around.

deleted 3y ago

[deleted]

glimshe 3y ago

It's somewhat humorous that the most expensive part is the manual! And no wonder electronics nowadays stopped including comprehensive manuals like the Spectrum's in their aggressive cost cutting.

mchannon 3y ago
Making a second, third, or fourth set of manuals would have obtained substantial economies of scale whether in the 20th or 21st centuries. There was a time where PDF didn’t exist, there were no tools to create, let alone view or print manuals. Even when these became widespread, a number of troglodytes would get bent out of shape if their new appliance didn’t come with a (preferably bound!) paper manual. Most of these folks have either passed on or begrudgingly assimilated.
- SoftTalker 3y ago
  I'm kind of in that camp with cars. The last car I bought didn't come with an owner's manual. I've "begrudgingly" accepted that a PDF copy on my phone is for most practical purposes just as good, but I still prefer the paper. It's just easier to read, thumb through, or check the index and find what I'm looking for than doing the same on a small touch screen.
  - jaredhallen 3y ago
    Agreed. I buy real factory service manuals for any car I plan to keep for any length of time. They go for about $100 on eBay and are worth every penny.
mananaysiempre 3y ago
For small-run offset printing (as opposed to laser-printer-quality stuff you get from print-on-demand shops, including PoD reissues of old titles the big academic publishers sell under the guise of new copies), the books themselves are basically free compared to the plates. A bookshop owner who also worked in printing once told me it was in the order of $1M for the plates for a 300-page book, and then negligible costs for the actual books until you get past at least tens of thousands of copies. So printing one manual or a hundred of them is a very different proposition from a normal-sized run of like 50k of them.

TillE 3y ago

I love projects like this. It's even simpler to just homebrew your own 8-bit computer / game console from widely available parts, and a great way to learn about and really understand how computers work. Computers have become far more complex, but the broad fundamentals are basically unchanged since the 1970s.

wkjagt 3y ago
I did Ben Eater's 6502 kit and expanded on it a lot. You're right, it really gets you to appreciate how computers really work, in a much simplified way of course, compared even to for example the first IBM computer. Implementing something like a FAT file system for example also really makes you appreciate the deeper concepts of how an OS works. I only did a very simple FAT implementation, without subdirectories, but even with that, terms like FAT and sector became very concrete things instead of vague concepts.
- eek2121 3y ago
  Ben Eater is awesome. I knew most of the stuff for x86, but revisiting all the things on a breadboard for 6502 and peripherals? AWESOME.Note of the snobbish: you can even build your own graphics card.

urbandw311er 3y ago

I loved this. Did he shrink wrap it only to then immediately rip it open?

vsviridov 3y ago

So, a 100 pounds in the 80s is almost 500 pounds today, according to the UK inflation calculator. So his build total cost is below that... Arguably 100£ was the retail price, not costs, but still

xyzzy3000 3y ago
For those wanting a link: https://www.bankofengland.co.uk/monetary-policy/inflation/inflation-calculator https://www.bankofengland.co.uk/monetary-policy/inflation/in...

azurefan 3y ago

Pretty cool post. I’ve been playing spectrum games recently http://torinak.com/qaop/games http://torinak.com/qaop/games

ConanRus 3y ago

Back in the end of 80s - 90s in the USSR/Russia were were lots of ZX Spectrum variants, and none of them had the ULA. They all were engineered to use the most popular and easy to obtain components. So i believe you still can build one for cheap. This one was one of the most popular variants https://en.wikipedia.org/wiki/Pentagon_(computer) https://en.wikipedia.org/wiki/Pentagon_(computer)

lovegrenoble 3y ago

You brought back my childhood memories, thank you!

Wajeez 3y ago

If we were to upgrade that hardware design to say Speccy 4 or 2023 for that matter... What CPU, GPU, and OS would we use?