The Sinclair ZX Spectrum was extremely in style within the early ‘80s as a result of it was fairly succesful and extraordinarily reasonably priced. In international locations just like the UK, it was liable for introducing giant swaths of the inhabitants to computing — much like the Commodore 64 in america. And, in fact, Sinclair guarded their beneficial mental property and wasn’t eager on sharing it. However the Soviet Union wasn’t identified for respecting mental property and the Soviets reverse-engineered the ZX Spectrum to make a private pc for the folks. Redditor MadCatUS used among the ensuing Soviet schematics to construct their very own ZX Spectrum.
Many ZX Spectrum clones appeared within the Soviet Union all through the Eighties and even into the Nineteen Nineties. They have been spectacular feats of reverse-engineering in their very own proper, as a result of the ZX Spectrum was a mysterious machine. The ULA (Uncommitted Logic Array) chip, particularly, was one thing of a black field, however was essential for performance. To oversimplify issues, it acted as an middleman between the Z80 CPU and the remainder of the {hardware}. As a result of the ULA chip was so tough to reverse-engineer, many Soviet ZX Spectrum clones omitted it fully and used extra typical chips as a substitute.
That’s precisely what helped MadCatUS construct their very own ZX Spectrum. They used the schematics for the Дельта‑С (“Delta-S” in English), which works with no ULA chip and is subsequently simpler to recreate right now.
Working from the unique Soviet Delta-S schematics, MadCatUS rigorously reproduced the circuitry of the mainboard in KiCAD. Whereas they have been at it, in addition they threw in some upgrades, like a 128k RAM mod and floppy drive integration. As soon as they have been proud of the design, they have been in a position to have a prototype PCB fabricated. They then populated it with the suitable chips — some are NOS (New Outdated Inventory) from the Soviet period, whereas others are nonetheless produced and will be purchased new.
The Sinclair ZX Spectrum was notorious for its atrocious keyboard and MadCatUS wished one thing higher, so in addition they designed their very own keyboard with good Cherry MX key switches. Lastly, they modeled a 3D-printable enclosure to carry every part. It isn’t a direct copy of the Delta-S, but it surely has comparable brutalist aesthetics. The massive distinction is an extension on one facet to accommodate the floppy drive.
That is nonetheless a piece in progress and MadCatUS must perform a little bit extra work to shine every part up. However it’s already purposeful and so they may even run ZX Spectrum video games on this fascinating historic recreation.
