[HN Gopher] Talking to memory: Inside the Intel 8088 processor's...
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Talking to memory: Inside the Intel 8088 processor's bus interface
state machine
Author : todsacerdoti
Score : 64 points
Date : 2024-04-28 15:47 UTC (7 hours ago)
(HTM) web link (www.righto.com)
(TXT) w3m dump (www.righto.com)
| kens wrote:
| Author here for your 8088 questions...
| thrtythreeforty wrote:
| Not a question but a suggestion. You should also do a similar
| article for the 8061 series processor. This was a special
| processor used at least in the Ford EEC-IV (Fox body Mustangs,
| 1990s F-150s, etc), notable for its very wacky "M-BUS" memory
| bus. They wanted to conserve pins (I guess for more GPIO) so
| they replaced the normal bus with a bidirectional 8-bit bus,
| with a couple registers set in the memory chip which represent
| the data pointer or program counter. At any point the processor
| can request data from either of those two pointers with a
| couple dedicated signals STB, IT, and DI, and the program
| counter pointer is supposed to auto-increment.
|
| The whole thing is a very complex pair of state machines and
| it'd be interesting to go over the protocol. It's been
| documented in a difficult-to-read Ford programmers guide, but
| largely unheard of otherwise.
| NanoCoaster wrote:
| Not a question, just wanted to say I'm a big fan of your blog
| and have been binge-reading it in recent times. I really enjoy
| the way you explain concepts like transistor types, digital
| logic and chip design in a way that even somebody like me,
| who's still pretty new to this low-level look at hardware, can
| understand. I also appreciate that you sometimes use the same
| intro or explanations in multiple blog articles, so readers can
| just pick up whatever they're most interested in and don't have
| to go through everything that came before.
|
| Ah, I do have a question: Any chance of an article about the
| Gameboy CPU someday in the future? :)
|
| I'm writing an emulator for it at the moment and find it to be
| quite an interesting chip from this perspective - such a weird
| crossover between a 8008 and Z80 (if I remember correctly).
| doubloon wrote:
| How did they test and debug this stuff in the 70s
| phire wrote:
| For the 8086 they had a gate level simulator called LOCIS. The
| problem is that intel historically designed everything at the
| transistor level, so the 8086 didn't map onto a gate level
| simulation very well.
|
| The "Coping with the Complexity of Microprocessor Design at
| Intel - A CAD History" paper [1] goes into details of what they
| used in the 80s and onwards, but it does briefly mention what
| they were doing before that.
|
| [1] https://www.researchgate.net/profile/Avinoam-
| Kolodny/publica...
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