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No Moore Left to Give: Enterprise Computing After Moore's Law
1. No Moore Left to Give
Enterprise Computing After Moore’s Law
CTO
bryan@joyent.com
Bryan Cantrill
@bcantrill
2. Moore’s Law?
• Which of these is Moore’s Law?
1. “Transistor speed increases exponentially over time”
2. “Transistors per dollar grows exponentially over time”
3. “Transistor density grows exponentially over time”
4. “The number of transistors in a package grows
exponentially over time”
3. Moore’s Law?
• Which of these is Moore’s Law?
1. “Transistor speed increases exponentially over time”
2. “Transistors per dollar grows exponentially over time”
3. “Transistor density grows exponentially over time”
4. “The number of transistors in a package grows
exponentially over time”
• Answer: All of them — and none of them!
16. So… Moore’s Law?
• In the 1965 paper, there is no Moore’s Law per se — just a
bunch of incredibly astute and prescient observations
• The term “Moore’s Law” would be coined by Carver Mead in
1971 as part of his work on determining ultimate physical limits
• Moore updated the law in 1975 to be a doubling of transistor
density every two years
• Dennard scaling would be outlined in detail in 1974
• But for many years, Moore’s Law could be inferred to be
doublings of transistor density, speed, and economics…
17. Moore’s Law: Good old days?
• The 1980s and 1990s were seemingly great for Moore’s Law…
• But even in those halcyon years, memory was not speeding up
relative to the CPU — we were hitting the memory wall
• Symmetric multiprocessing became the clear path for delivering
single-system throughput on multi-threaded workloads…
• …but SMP didn’t help single-threaded performance, which
needed aggressive speculative execution to achieve low CPI
• SMP and speculative execution were both fraught with peril:
even the good old days of Moore’s Law were still a challenge!
18. Moore’s Law: Beginning of the end
• Dennard scaling ended in ~2006 due to current leakage…
• …but by then chip multiprocessing was clearly the trajectory
• CMP was enhanced by simultaneous multithreading (SMT),
which offered another factor of two on throughput…
• Thanks to experience with SMP, CMP/SMT was less of a
software performance apocalypse than many had feared — but
more of a security apocalypse than anyone anticipated!
• …but “dark silicon” threatened to limit CMP
19. Moore’s Law: Crossing the rubicon
• As feature sizes continued to shrink to 28nm and then 22nm, a
critical rubicon was crossed:
Source: “Why Migration to 20nm bulk CMOS and 16/14nm FinFETs is not best approach for semiconductor industry” (Handel Jones, IBS, 2014)
20. Moore’s Law: Crossing the rubicon
• Moving to 20nm and beyond required solving some nasty and
very expensive problems, necessitating FinFETs
• We were adhering to one definition of Rashomon’s Moore’s Law
(density) but not the more important definition (economics)
• Moore’s Law was not — or should not have been — merely
about density at any cost!
21. Moore’s Law: End of the end?
• In August 2018, GlobalFoundries suddenly stopped 7nm
development, citing economics and lack of demand
• GlobalFoundries departure left TSMC and Samsung on 7nm —
and Intel on 14nm, struggling to get to 10nm
• Intel’s 10nm Cannon Lake is now three years late — and for Ice
Lake/Cascade Lake, Intel will intermix 14nm and 10nm
• Moving to 3nm/5nm will require moving beyond FinFETs to
GAAFETs — and to EUV photolithography
22. Moore’s Law: Really, the end
• Even if narrowly interpreted to be an exponential increase in
transistor density over time at any cost, Moore’s Law is ending
• A silicon atom is 0.2nm wide — 3nm is very close to the end on
that basis alone!
• Whether or not the industry can get to 3nm/5nm or not isn’t the
question — the question is at what cost
• Economically, Moore’s Law is indisputably over
• What does this mean for the enterprise?
23. Beyond Moore’s Law: Quantum computing?
• Quantum computing is an interesting and laudable idea — and
becoming surprisingly real! (viz. IBM’s Q System One)
• But:
• The problem domain is very limited
• The economics are entirely unknown
• The scale is still tiny — and there doesn’t yet appear to be a
Moore’s Law for qubits
• Quantum computing may be relevant one day for the enterprise,
but no time soon
24. Beyond Moore’s Law: Specialized compute?
• Specialized computing is already important in several
commercially relevant problem domains, e.g. GPGPU for ML/DL
• This will continue, though hardware design/verification cycles
will demand the problem domains to be well-specified
• When implemented as ASICs and (especially) FPGAs, use of
older CMOS nodes may inhibit some performance gain
• Transistor limits will apply to specialized compute as well —
specialized compute will quickly hit the accelerator wall
25. Beyond Moore’s Law: 3D?
• 3D (vs. planar) has proven to work well for some components
(e.g., 3D NAND on an older CMOS node)…
• …but using 3D for CPUs may pose heat, yield and potentially
cost problems
• Intel is actively investing in 3D via Foveros
26. Beyond Moore’s Law: 2.5D Chiplets?
• One very promising approach is to make smaller chiplets that
are then integrated into a larger die with a through-silicon via:
Source: “Cost-Effective Design of Scalable High-Performance Systems Using Active and Passive Interposers” (Stow et al.)
• Chiplets allow different functions (e.g. CPU, GPU) and different
processes (e.g. 7nm, 14nm) on the same die
• AMD is using chiplets for EPYC; Intel is investing in EMIB
27. Beyond Moore’s Law: Alternative physics?
• There are tons of alternative physics out there: silicon
photonics, carbon nanotubes, phase change memory, etc.
• All of these are worthy of exploration and productization!
• History indicates that promise is insufficient: they must be able
to compete with the economics of the technologies that they will
displace
• When they break through — e.g., flash memory — they can
change the entire industry
• So watch them and cheer for them — but don’t assume them
28. Beyond Moore’s Law: Wright’s Law?
• In 1936, Theodore Wright studied the costs of aircraft
manufacturing, finding that the cost dropped with experience
• When volume doubled, unit costs dropped by 10-15%
• This has been dubbed the learning curve effect
• In 2013, Jessika Trancik et al. found Wright’s observation held
predictive power for semiconductors
• Could this hold true for the 7nm node or for older nodes like
14nm? Could transistors start getting cheaper again?
29. Beyond Moore’s Law: Compute everywhere?
• Especially if and as highest-density compute becomes cheaper,
we will see many more CPUs — and in many more places
• We are already seeing CPUs on the NIC (SmartNIC), CPUs
next to flash (e.g. open-channel SSD) and on the spindle (e.g.
Western Digital’s SweRV, based on RISC-V)
• These promise to deliver higher-performing abstractions — but
with concomitant increases in overall system complexity!
• Left unchecked, there are potentially terrifying security
ramifications; comprehensive systems design is called for!
30. Beyond Moore’s Law: Durable computing?
• Assuming that we are indeed on 7nm for a protracted period of
time, should we still be replacing host CPUs every 3 years?
• How long can a CPU last, anyway?
• Should we be exploring more durable computers?
• Should we be looking to other axes of improvement with respect
to density or power?
• e.g., Open Compute Project — and specifically the Intel Twin
Lakes (Xeon D-2100) for OCP Yosemite V2
31. Beyond Moore’s Law
• The end of Moore’s Law is a change — but the truth is that we
have always had engineering challenges at every level of the
hardware and software stack
• The future will be no different: the complexion of the problems
may change — and we may focus more on efficiency and
density as raw power — but it remains alive with promise
• For software engineers, there will be new opportunities to
understand and optimize for the hardware beneath us!
• Beyond Moore’s Law, we must increasingly think of the system:
hardware and software designed together!
