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74xx

SPAM-1 Is A Well-Documented Discrete CPU With An Impressive Software Library

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Right Here at Hackaday we enjoy tasks that are so well-documented that you can invest days researching what the developer has actually accomplished. [John Lonergan] really did not dissatisfy when he made the SPAM-1, an 8-bit CPU constructed from distinct reasoning entrances. His thorough log consists of a riches of info on such points as developing opcodes, enhancing program counter reasoning, running an electronic simulation, in addition to his ideas on microcode style. The large quantity of it might be a little bit repulsive to novices, so it could be best to begin with the video series that explains the design and also explains on a number of sub-blocks.

The style has actually altered a little bit considering that [John] initially began on the job, as he made a decision to include increasingly more functions, yet the result is a well-thought out design that maintains the simpleness required for distinct equipment yet still has adequate functions to maintain it fascinating for experienced CPU enthusiasts. The guideline dimension is instead huge (48 little bits) to streamline the guideline decoding at the expenditure of bigger code dimension. Conditional dive guidelines are absent; rather, all guidelines have an optional control flag to make them conditional, an attribute influenced by the ARM guideline collection.

Once the style was fully grown sufficient, [John] designed the whole point in Verilog and also substitute his style to confirm proper procedure and also to inspect the timings, approximating it to be practical approximately 5 MHz or two. A huge pile of breadboards and also DIP chips from the 74xx collection after that brought the style to life.

Not material with merely developing, imitating and also applying a personalized CPU in equipment, [John] likewise invested considerable initiative on the software application side of points, creating an assembler and also also a C-like compiler for the SPAM-1 system. As well as if that had not been sufficient, he likewise included an emulator for the traditional CHIP-8 language, which permits it to run existing programs like Pong and also Tetris. Input and also outcome for all this software application is mainly with a UART link to a COMPUTER. A VGA user interface is still on [John]’s order of business, yet he did develop an adapter to connect a classic NES controller to the system.

The SPAM-1 is a deserving enhancement to the lengthy checklist of discrete-logic CPUs we have actually seen right here, such as this breadboard computer system running a UNIX-like OS or this minimalistic one. If you wish to see one that executes an existing guideline collection, attempt this homebrew RISC-V computer system.

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1 MHz

Homebrew 16 Bit Computer Reinvents All The Wheels

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Structure your very own computer system has several feasible courses. One can produce their very own Z80 or MOS 6502 computer systems and after that run a duration appropriate OS. Or an individual can go back to square one as [James Stanely] did. [James] has actually developeda completely unique computer and CPU he calls SCAMP Cheat runs a custom-made OS called SCAMP/os which you can look into in the video clip listed below the break.

[James] explains the CPU and also computer system as actively primitive. Constructed out of distinct 74xx collection reasoning chips, it goes for a fast-enough-for-homebrew 1 MHz. And also, it has a great deal of strobe lights that can not assist yet advise us of the initial Imsai 8080. However as opposed to a panel of buttons for programs, the SCAMP/os boots to a covering, which exists via a serial terminal. Programs are created in a custom language with its very own compiler. The OS is called a having a Unix-like feeling with CP/M-like performance. That’s rather a mix!

What we enjoy most regarding the construct, besides its tidy appearances and also blinkenlights, is the quantity of job that [James] has actually taken into recording the construct both on his blog and also onGithub, where the source code and design is available There’s additionally an open invite for factors to assist progress the job. We make sure he’ll arrive, one little bit at once.

While [James] is utilizing a Compact Flash card for storage space presently we can not assist yet question if a Cassette Tape storage space system could be a beneficial future upgrade.

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