The Sinclair ZX Spectrum was extremely widespread within the early ‘80s as a result of it was fairly succesful and extraordinarily inexpensive. In international locations just like the UK, it was answerable for introducing giant swaths of the inhabitants to computing — just like the Commodore 64 in america. And, after all, 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 laptop for the individuals. Redditor MadCatUS used a number of 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 Nineties. They had 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 crucial 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 troublesome to reverse-engineer, many Soviet ZX Spectrum clones omitted it totally and used extra standard 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 out a ULA chip and is subsequently simpler to recreate in the present day.
Working from the unique Soviet Delta-S schematics, MadCatUS fastidiously reproduced the circuitry of the mainboard in KiCAD. Whereas they had been at it, additionally they threw in some upgrades, like a 128k RAM mod and floppy drive integration. As soon as they had been proud of the design, they had been in a position to have a prototype PCB fabricated. They then populated it with the suitable chips — some are NOS (New Previous Inventory) from the Soviet period, whereas others are nonetheless produced and could be purchased new.
The Sinclair ZX Spectrum was notorious for its atrocious keyboard and MadCatUS needed one thing higher, so additionally they designed their very own keyboard with good Cherry MX key switches. Lastly, they modeled a 3D-printable enclosure to carry all the pieces. 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 all the pieces up. However it’s already purposeful and so they may even run ZX Spectrum video games on this fascinating historic recreation.
