kens

70 ms·

871.
by kens 3y ago
> It makes a great solvent, so let's put in anesthesia? Literally, yes. The potency of an inhalation anesthetic is usually directly proportional to its lipid solubility. (Known as the Meyer-Overton correlation.) This is why solvents
872.
by kens 3y ago
I think CALL/RET are mostly arbitrary, where there were free opcodes. But RET iw and RETF iw share the microcode, using bit 3 of the instruction to distinguish them. So they need to have opcodes differing only in bit 3.
873.
by kens 3y ago
I don't think there's any practical reason to do that unless you want to get into the retrocomputing community.
874.
by kens 3y ago
Thanks! I've been doing too much IBM System/360 stuff and I can't remember which way to count bits :-)
875.
by kens 3y ago
Author here if anyone has 8086 questions...
876.
by kens 3y ago
Nowadays, people think of just vacuum tubes and then transistors, but in the 1960s there were a lot of different technologies being used. For example, superconducting cryotrons, magnetic core logic, parametric-phase-locked-oscillator logic,
877.
by kens 4y ago
Knuth's comments on optimization are very nuanced. I beg people to not use the phrase "premature optimization" without reading what he actually said. See page 8 of https://pic.plover.com/knuth-GOTO.pdf
878.
by kens 4y ago
No, the iAPX 432's successor was the Intel i960, which confusingly is completely unrelated to the i860. By the way, it's interesting to read the iAPX 432 architecture paper along with the Case for RISC paper, since the 432 paper a
879.
by kens 4y ago
The 97,000 transistor count number is from Wikipedia. The number appears to be fictional and doesn't match other sources so I marked it as [citation needed].
880.
by kens 4y ago
Thank you for this very helpful suggestion! I got in touch with Tom and he does have some 432 chips.
881.
by kens 4y ago
Was your roommate working on the 432 performance paper? (Paul M. Hansen, Mark A Lirdon, Robert N. Mayo, Marguerite Murphy, and David A Patterson)
882.
by kens 4y ago
The ironic thing is that the performance analysis paper [*] found that the weird bit-aligned instructions iAPX 432 didn't actually help code size. "Although the 432 has bit-variable length instructions, it requires more space than
883.
by kens 4y ago
Yes, those papers were very informative. Also the iAPX 432 patents have a lot of detail: https://patents.google.com/patent/US4325120A https://patents.google.com/patent/US4367524 https:/&#x2F
884.
by kens 4y ago
Author here if there are any questions. Also, if anyone happens to have other iAPX 432 chips sitting around, I'd be happy to take high-resolution die photos. There aren't good 432 die photos around, so I was happy to get access to
885.
by kens 4y ago
I'm curious about why exactly this is so anxiety-inducing. I have multiple hypotheses: a) the way the numbers only come together for a moment means you need to concentrate. b) the feeling of objects being flung towards you. c) the colo
886.
by kens 4y ago
Fujitsu decided to stop manufacturing semiconductors around 2014. This was part of a "series of realignments"; Fujitsu decided to focus on information technology and cloud computing due to foreign competition. Ref: https:/&#
887.
by kens 4y ago
Yes, computers can handle base 20. The IBM 1401 business computer (1959) could optionally support pounds/shillings/pence in hardware, where there were 20 shillings in a pound and 12 pence in a shilling. (Britain switched to decima
888.
by kens 4y ago
The article mentions a couple of formulas for the ranking algorithm. I'd like to point out my data-driven reverse-engineering of the HN ranking algorithm from 2013. The basic ranking formula uses votes and age with various exponents. B
889.
by kens 4y ago
Yes, REP IDIV will negate the quotient. Andrew Jenner discusses that: https://www.reenigne.org/blog/8086-microcode-disassembled/
890.
by kens 4y ago
Andrew Jenner pointed out that the microcode for the string (block move) operations doesn't exactly match the flowchart in the documentation, and the micro-instructions are kind of scattered around. So it's likely that the string
891.
by kens 4y ago
The 8086/8088 look pretty well-optimized in many ways: the design of the instruction set, the architecture, the microcode, and the silicon layout. Studying it closely, I've seen multiple things that are more clever than I expected
892.
by kens 4y ago
Author here. Hopefully you're not all tired of the 8086 by now :-)
893.
by kens 4y ago
It's strange that computer programmers think of themselves as being on the cutting edge of technology, but then we use a language that is over 50 years old. Of course there are going to be lots of problems with C strings since they wer
894.
by kens 4y ago
I like challenging books but found Gravity's Rainbow annoying and tedious, although I made it to the end. I got halfway through Mason & Dixon before giving up. I figured Bleeding Edge would be better because it's about compute
895.
by kens 4y ago
I didn't think about a solution too deeply, but I was thinking of something like "shadow" prefix registers: when the chip takes an interrupt, copy the prefix latches to the shadow register, and then when you return from the i
896.
by kens 4y ago
The original segment registers were RC (code base), RD (data base), RS (stack base), and RA (alternate). I think the "R" is for "relocation register". But in the microcode, DA used the alternate segment, DD used the data
897.
by kens 4y ago
I think the argument for low pin counts was that Intel had a lot of investment in manufacturing and testing to support 16 pin packages, so it would cost money to upgrade to larger packages. But from what I read, it seems like one of those t
898.
by kens 4y ago
It seems obvious to access DRAM that way, but multiplexing the address pins was a big innovation from Mostek for the 4K RAM chips, and they "bet the company" on this idea. Earlier DRAMs weren't multiplexed; Intel just kept ad
899.
by kens 4y ago
Not a typo, but something I should clean up. The move instruction moves from DS:SI to ES:DI. The 8086 registers originally had different names (which is why AX, BX, CX, DX aren't in order) and the "Extra Segment" was the &quo
900.
by kens 4y ago
I think the motivation is that the address adder already has the capability to increment/decrement registers by various constants: incrementing the PC, incrementing the address for an unaligned word access, correcting the PC from the q

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