Live data from Hacker News

Die analysis of the 8087 math coprocessor's fast bit shifter (2020)

righto.com

21–22 of 22 posts

Re: Die analysis of the 8087 math coprocessor's fast bit shifter (2020)

#21
post #11

Earlier quoted context omitted.

That's a very interesting board! It came out in 1976 (four years before the 8087) and cost $499 assembled, equivalent to $2900 in current dollars, so it was expensive. It was really a decimal processor built from simple TTL parts, and had four microcoded instructions: add, subtract, multiply, and divide. Arithmetic used the 74LS181, the very popular ALU chip. (It did multiplication with repeated addition; there's no…

My mistake -- what I wrote was from memory so I got the bit wrong about the multiplier ROM. I must have confused that detail with the design of the Wang 2200 computer, which had double precision BCD float math and did in fact have a 4b x 4b multiplier ROM. https://www.wang2200.org/ (I'm the guy behind the wang2200.org domain)

Lovely page, I enjoyed it lots. Especially this: “The first time I programmed a computer was in the fall of 1978 at LTHS, Lyons Township High School, in La Grange, IL. It changed my life. For a long time I couldn't think of anything else but programming computers, and it hasn't yet completely worn off.” Calms me down and gives hope. I started feeling like losing the programming spark is just behind the corner more and more during the past decade (working for money), yet decade and some before that was so exhilarating. But now I think, you've started 20 years before I was born!

Re: Die analysis of the 8087 math coprocessor's fast bit shifter (2020)

#22
Always amazed how spoiled we are with modern hardware! The 8087 was $500 in today's dollars, and delivered around 50 kFLOPS of performance (0.00005 GFLOPS).

A cheap mobile phone CPU+GPU costs the manufacturer maybe $20, and typically does 50 GFLOPS on the CPU and 500+ on the GPU. So 10 million times the performance for 1/25th the cost.

Humbling too how "worthless" all the incredible ingenuity of the 8087 circuits and die designs now is, although I'm sure many of those innovations live on in modern chips.

Post reply on HN