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| retro8 - a CPU and computer for the 8 bit era http://anycpu.org/forum/viewtopic.php?f=3&t=795 |
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| Author: | BigEd [ Wed Oct 28, 2020 8:47 am ] |
| Post subject: | retro8 - a CPU and computer for the 8 bit era |
. @jecel over on retrocomputing forum has just posted a writeup of his 8 bit CPU design - and associated computer design - which he put together in response to a challenge on G+ back in 2013. It's an 8 bit machine, 12 registers, relatively regular but not CISC, and the kicker is that addresses are 24 bits (and the registers come in sets of 3) See here: Retro8 - what would have been the ultimate 8 bit micro? It's a squeeze, but Jecel has assigned a 40 pin pinout too - and also a 28 pin pinout! |
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| Author: | robfinch [ Wed Oct 28, 2020 12:18 pm ] |
| Post subject: | Re: retro8 - a CPU and computer for the 8 bit era |
That is an interesting machine, but where are the load and store instructions? |
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| Author: | BigEd [ Wed Oct 28, 2020 12:29 pm ] |
| Post subject: | Re: retro8 - a CPU and computer for the 8 bit era |
It's a cunning plan: most opcodes take 4 bits to specify the 'register', which gives 12 codes for the one-byte registers, and 4 codes for indirection through the 4 triple-size clusters. Another format uses 2 bits to specify the 4 triplets. |
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