> 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.
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.
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.
Just publishing on the web wasn't an option at the time. But damn! I remember reading at the back of a C64 manual as a kid. Trying out the various "commands". I had no concept of "programming" or "basic". This was just how the machine worked and I was occasionally in the mood of figuring it out. That time will never come again, for me or anyone else.
I was barely beginning to read when I got the manual. And it wasn't in my primary tongue. Illustrations showing how to connect the pieces and what buttons to press
[L][O][A][D] [RETURN]
Enabled me to start following the instructions without knowing any English. What a brilliant manual it was!
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.
Those must have been some expensive plates. We did a vanity run of a small book and it was 10k copies for about $20k around 2000 or so - and half that was the plates.
The Spectrum manual was good, with the usual programming guide and a breakdown of the memory map and system variables, but the Jupiter Ace manual also included example circuits so you could build your own peripherals...
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.
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.
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.
The cost for the manuals seems high--at least if you're willing to have some flexibility on paper choice. I'd think that one volume print on demand from Amazon would be more like $10 although it's admittedly been a while since I looked at pricing.
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
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.
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.
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.
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).
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.
It uses a Xilinx XC95144 CPLD to emulate the ULA: https://docs.xilinx.com/v/u/en-US/ds067