Amin Shokrollahi

52 Pages·2016·12.46 MB·English

A
 Theory
 of
 Coding
 for
 Chip-­‐
to-­‐Chip
 Communica6on
Amin
 Shokrollahi

and
 the
 engineering
 team
 of
 Kandou
Dagstuhl - August 2016
The
 Problem
Dagstuhl - August 2016
Chip-­‐to-­‐Chip
 Communica6on
1 2

p p
i i
h h
C C
Communica)on

wires
Dagstuhl - August 2016
Abundant….
Dagstuhl - August 2016
Noise
1 2

p p
i i
h h
C C
Noise
 scales
 badly
 with
 frequency
 of
 transmission:

Example:
 -­‐40dB
 at
 frequency
 f,
 -­‐90dB
 at
 2f
Signal
 strength
  Signal
 strength

drops
 to
 ~1%
  drops
 to

 ~0.003%
Dagstuhl - August 2016
Power
Supercomputers Data centers
Internal traffic in Giga-
1E+12 4E+11
bits per second
Power in Mega-Watts 20000 8000
Mul6ply
 by
 4
 in
 every
 genera6on
 (~2
 years)

Very
 par6ally
 offset
 by
 Moore’s
 law
Dagstuhl - August 2016
Point
 in
 Case
“While
 CPU’s
 doubled
 performance
 every
 two
 years,

evolu6on
 from
 1
 GigE
 to
 10GigE
 took
 12
 years,
 and
 WAN

routers
 increased
 throughput
 only
 4-­‐fold
 during
 the
 same

6me
 period.”
 [6]
Andy
 Bechtolsheim,
 2012
Dagstuhl - August 2016
Capacity
) 450 ~20x
s
p
b
400
G
(
350
e
r
i
w
300

r
e
p 250

t
u
200
p
h
g
150
u
o
r
100
h
T
50
2 4 6 8 10 12 14 16 18
Today
Std dev of noise (mV)
Dagstuhl - August 2016
Channel
 is
 NOT
 Similar
 to….
Or
 any
 channel
 with
 a
 lot
 of
 “random”
 noise
Dagstuhl - August 2016
Noise
Deterministic Random
SSO Ref Xtlk EMI CM ISI Thermal
Almost
 all
 noise
 is
 determinis6c

but
 resources
 are
 6ght
Dagstuhl - August 2016