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I am attempting to build a simple CPU from only BJT transistors. It will have a bus so I will need some tri-state buffers.

Can I/should I build them, or should I buy a chip? Is the risk of damaging the transistors with static electricity and sorts not worth it?

JRE
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joupy
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    A very warm welcome to the site. Please note that it's a Q&A site, not a discussion forum or free design house. You may be better off on an electronics discussion forum instead. People here will help you take the next step if your question shows you've already done as much as you possibly could - which yours doesn't, I'm afraid. Please edit your question and greatly improve it. In considerable detail, explain why you are doing this, show your own work and findings with any schematic. The better the quality of your question, the better the quality of the answers it will attract. Again, welcome. – TonyM Jan 05 '22 at 11:24
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    If you're going to build it from BJTs, build the whole thing from BJTs. If you're going to wuss out and put some chips in there, then you might as well just build the whole thing from chips, or better still, buy an Arduino. – Neil_UK Jan 05 '22 at 11:54
  • @dim thx, deleted – Neil_UK Jan 05 '22 at 12:22

2 Answers2

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If you are going down to a BJT level to build a CPU, building the buffers wont be much extra work compared to the rest.

11011100
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If you want to build retro computers, then I'd suggest you do some research into how computers were built with transistors in the 50's and 60's. I don't think you'll find tri-state buffers. Why? Very expensive to implement. You'll most likely see open collector (wired or) busses as they are much simpler to implement.

Two examples come to mind - the IBM1401 as there are extensive write ups on how it is implemented and the CDC6600 - one of the designers wrote a book on it which is in the public domain now. https://archive.computerhistory.org/resources/text/CDC/cdc.6600.thornton.design_of_a_computer_the_control_data_6600.1970.102630394.pdf

In short, depending on the actual hardware implementation, different techniques are used to capitalise on the specific advantages. How you design and implement a computer using transistors is quite different to using TTL, an FPGA or a custom design in silicon.

Kartman
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