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One measure of a pc’s bit width is the scale of the CPU’s registers. For instance, a number of early 8-bit house computer systems used an “8-bit” 6502 processor. And whereas computer systems later got here with 16-, 32-, 64-, and extra bits, a Japanese electronics maker generally known as naoto64 went the other way with the problem of constructing a 1-bit CPU with logic chips. This laptop could be the head of low-performance computer systems as a result of it’s only able to two directions, leading to a blinking (or regular) LED.
The 1-bit CPU design makes use of 4 7400-series logic built-in circuits (ICs) to implement all the essential CPU blocks on the straightforward printed circuit board (PCB). The PCB additionally comprises 4 dip switches, USB-C (for fundamental energy), 4 LEDs, and a push button.
On the core, a quad-NAND gate types an XOR-based arithmetic unit. In fact, this design means the 1-bit CPU solely has a single math operation: 1-bit ADD! Nevertheless, it additionally has a JMP instruction that enables repeated use of the exclusive-or. 4 dip switches make up the four-bit read-only reminiscence (ROM.) Three attainable packages management the LED packages on, off, or toggling.
Why is that this a single-bit CPU? One component of the twin 7474 flip-flip types a 1-bit information register, and the opposite types a program counter by utilizing the output and its complement. Three gates of a 7414 (Schmitt Set off) inverter with passives create an approximate 1 Hz clock to drive the 1-bit CPU.
The spirit of this venture design reminds us of the MyNOR single-board laptop. Dennis Kuschel constructed a floating level calculator round a CPU fabricated from solely a single NOR gate in that venture.
Whole 1-Bit CPU design (📷: naoto64)
The design is intelligent even when the 1-bit CPU doesn’t construct a sensible laptop. Its schematic is price trying over. One of many extra spectacular features of the design is that it totally makes use of all the weather within the 4 logic ICs!
The Japan-based on-line retailer Change Science sells the 1-bit CPU package for 2500 Yen. You may also obtain the KiCad design information and Gerbers from naoto64’s GitHub repository. All of the documentation is in Japanese, however machine translation companies do a good job translating them.
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