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A project log for ED-64: A discrete 8-bit computer

ED-64 will be an 8-bit computer built with discrete components, and will feature a ferrite core memory (documented as a separate project).

Andrew Starr 04/12/2017 at 09:016 Comments

An architecture and name change: the T-1 is now the ED-64, and it is no longer a stack machine. The changes were made for several reasons:

  1. I decided I really wanted to be able to load programs into the memory manually from the operator panel, and the Harvard architecture of the T-1 (and 10 bit program word) wouldn't allow that.
  2. For an 8-bit word formatted [Opcode][Address], a 2-bit instruction width means a 64-byte address space. Since I am avoiding multi-byte instructions, that means I only need to complete a single 64-byte core matrix (which I already have).
  3. Only 4 instructions drastically simplifies the control logic and ALU, while still allowing enough complexity to do interesting things.
  4. I got bored with the 'T-1' name!

Discussions

Andrew Starr wrote 04/12/2017 at 09:23 point

Oh well, now you can be fond of the ED-64 instead :) I'm looking forward to manually entering my first program!

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Andrew Starr wrote 04/12/2017 at 09:58 point

That's a neat idea - and would help simplify the operator panel. Got a part number, Yann?

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Yann Guidon / YGDES wrote 04/12/2017 at 10:08 point

No, unfortunately, I bought like a hundred on the electronic Bay from some broker... I don't regret the decision since I use them extensively :-D
I'll let you know if I find something...

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Yann Guidon / YGDES wrote 04/12/2017 at 10:14 point

not to be mistaken with "rotary encoder switch" which is a quadrature-encoded output...

It looks a lot like http://www.ebay.com/itm/1-B01-4-16-Rotary-Switch-5-Pin-or-Encoder-Click-Turn-NOS-USA-SELLER-/321436251671

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Yann Guidon / YGDES wrote 04/12/2017 at 09:19 point

That's sad, no more T-1 :-/ I was fond of it !

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