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Comparing difference between 8080 and PDP-8.

  • 8080 supports instructions of variable length, but does PDP-8?
  • Does PDP-8 support instructions of variable length?
Peter Cordes
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Rachel
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    Have a look at http://www.faqs.org/faqs/dec-faq/pdp8/section-3.html and eat you heart out, with all you've wanted to know about the PDP-8 instruction set. Most instructions are only 1 word long, some instructions are 2 words long. – Michaël Roy Apr 27 '20 at 17:46

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No, all basic PDP-8 instructions were 12 bits long.

If you added the EAE option (Extended Arithmetic Element) to add hardware multiply/divide, the address following a MUY or DVI held an address, and the address following a SHL, ASR, or LSR held a shift count, but those were such an exception that they were not considered multi-word instructions.

CJames
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