on FPGAs vs ASICs

Major Variola (ret) mv at cdc.gov
Sat Mar 19 11:11:25 PST 2005


Tyler, Riad, etc:

FPGAs are used in telecom because the volumes do not support an ASIC
run.
Riad doesn't seem to appreciate this.  He does understand that an ASIC
is more
efficient because its gates are used only for 1 computation, rather than
most
(FPGA) gates being used for reconfigurability ---useful if you can't
afford
an ASIC run (a million bucks a mask...) or if algorithms get tweaked
(eg you release before the Spec comes out, or you are shooting for
time-to-market).  Clockwise an FPGA wastes time in extra wire routing
although since an FPGA may be made in state of the art processes,
and your ASIC may not, its a complex tradeoff.  (Albeit some circuit
topologies
work very well on FPGAs)

So for the Cypherpunk wanting hardware (vs cluster) acceleration, FPGAs
are the way to go.  For TLAs, you prototype in FPGAs of course, and
then make some chips in your private fab.  (Same for Broadcom, etc.)

For someone making 10,000 routers, you use FPGAs.

DESCrack was solving a problem for which the x86 is not very efficient
at computing --all the sub-byte bit-diddling-- and hardware is very
efficient
(by design in DES, after all).





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