mark@mips.COM (Mark G. Johnson) (07/20/88)
In article <12005@ames.arc.nasa.gov>, lamaster@ames.arc.nasa.gov
(Hugh LaMaster) writes
$ Finally, I understand that handling the IEEE gradual underflow
$ behavior can add an extra cycle of latency. I also have
$ observed that the MIPS R2010 FPA (and maybe the new R3010 also)
$ can do a floating add in 2 (!) clock cycles. How did they do
$ that?
Yes, the R3010 also does IEEE 64-bit FP adds in 2 cycles. Architecture,
logic design, and circuit design of the R3010 are covered in a recent
article in IEEE Micro:
C. Rowen et al., "The MIPS R3010 Floating-Point Coprocessor",
_IEEE Micro_, Vol. 8 No. 3, June 1988, pp. 53-62.
The R3010's FP add unit's speed comes from 3 areas: (i) a hardware
"add algorithm" that's optimized toward implementation in full-custom
CMOS; (ii) an innovative logic partitioning / design that implements
the algorithm; (iii) highly polished CMOS layout and circuit
design. See the acknowledgments at the end of the paper if you're
interested in knowing who was responsible for each of these areas.
--
-- Mark Johnson
MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086
...!decwrl!mips!mark (408) 991-0208lindsay@k.gp.cs.cmu.edu (Donald Lindsay) (07/22/88)
In article <2626@quacky.mips.COM> mark@mips.COM (Mark G. Johnson) writes: >Yes, the R3010 also does IEEE 64-bit FP adds in 2 cycles. Architecture, >logic design, and circuit design of the R3010 are covered in a recent >article in IEEE Micro: > C. Rowen et al., "The MIPS R3010 Floating-Point Coprocessor", > _IEEE Micro_, Vol. 8 No. 3, June 1988, pp. 53-62. The article says "we chose a labor-intensive, hand-optimized design methodology". It goes on to mention 25 man-years across 16 months, and credits about 20 people. Only two of those people were credited for tooling - verification tools at that. Five people were credited with drawing. Wouldn't a bigger tooling effort have been worth it? -- Don lindsay@k.gp.cs.cmu.edu CMU Computer Science "Imitation is not the sincerest form of flattery. Payments are." - a British artist who died penniless before copyright law.