Way back (circa 1988ish timeframe) I remember a digital logic professor giving a little aside on the 8087 and remarking at the time that it (the 8087) used some three value logic circuits (or maybe four value logic). That instead of it being all binary, some parts used base 3 (or 4) to squeeze more onto the chip.
From your microscopic investigations, have you seen any evidence that any part of the chip uses anything other than base 2 logic?
The ROM in the 8087 was very unusual: It used four transistor sizes so it could store two bits per transistor, so the storage was four-level. Analog comparators converted the output from the ROM back to binary. This was necessary to fit the ROM onto the die. The logic gates on the chip were all binary.
Do you know what other prior systems did for co-processor instructions? The 8086 and 8087 must have been designed together for this approach to work, so presumably there is a reason they didn't choose what other systems did.
It is notable that ARM designed explicit co-processor instructions, allowing for 16 co-processors. They must have taken the 8086/8087 approach into account when doing that.
AMD's Am9511 floating-point chip (1977) acted like an I/O device, so you could use it with any processor. You could put it in the address space, write commands to it, and read back results. (Or you could use DMA with it for more performance.) Intel licensed it as the Intel 8231, targeting it at the 8080 and 8085 processors.
"On-Topic: Anything that good hackers would find interesting. That includes more than hacking and startups. If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity. "
pwg|17 days ago
Way back (circa 1988ish timeframe) I remember a digital logic professor giving a little aside on the 8087 and remarking at the time that it (the 8087) used some three value logic circuits (or maybe four value logic). That instead of it being all binary, some parts used base 3 (or 4) to squeeze more onto the chip.
From your microscopic investigations, have you seen any evidence that any part of the chip uses anything other than base 2 logic?
kens|16 days ago
I wrote about this in detail a few years ago: https://www.righto.com/2018/09/two-bits-per-transistor-high-...
rogerbinns|16 days ago
It is notable that ARM designed explicit co-processor instructions, allowing for 16 co-processors. They must have taken the 8086/8087 approach into account when doing that.
kens|16 days ago
Datasheet: https://www.hartetechnologies.com/manuals/AMD/AMD%209511%20F...
satiated_grue|13 days ago
https://en.wikipedia.org/wiki/Intel_8089
unknown|13 days ago
[deleted]
iberator|13 days ago
I mean: ZILOG probably already did it all in like 1982
andyjohnson0|13 days ago
"On-Topic: Anything that good hackers would find interesting. That includes more than hacking and startups. If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity. "
drob518|13 days ago