This month,
SiFive will launch an Arduino version of its open-source RISC-V processor on Crowd
Supply. In doing so, it spotlights the question of just how practical it is to
launch a new processor architecture when so many efforts to do so have failed,
especially when there are two perfectly good architectures available and there
are so many other ways to innovate — on top of the hardware.

The argument
for RISC-V goes something like this: It’s an inherently better architecture
than the x86 (complex instruction set computer, or CISC) or ARM (reduced
instruction set computer, or RISC); free is good; and being open and extensible
at the instruction-set level allows for unprecedented levels of innovation and
flexibility from “the community.”

Given the cost
of custom silicon, the need for ultra-low power, the dependence upon the x86,
and the uncertainty surrounding ARM with its buyout by Softbank, RISC-V’s star
is rising rapidly. It was hailed as “the Linux of microprocessor architectures”
by none other than Linley Gwennap’s Microprocessor Report, which signed off on
it as the best technology of 2016.

Of course, over
the years, we have seen many great technologies come and go: the famous
transputer, then Transmeta, and during the 1990s and early 2000s, there were a
host of wonderful signal-processing architectures to tackle wireless and wired
communications. But they’re gone. Why?

Putting
marketing and timing aside for now, it’s just plain hard to launch a new architecture:
Infrastructure support, software support, manufacturing, and related IP support
are just a few of the issues. Then there’s fear of the unknown: There needs to
be a really clear return on risk (RoR) for a designer to even think about
putting their company’s fortune on the line by selecting a new architecture, especially
when there are at least three perfectly good architectures available: x86, ARM,
and MIPS (also RISC).

The x86 and ARM
architectures are also well supported and have solid roadmaps. While there are
fees associated with using them, those fees are a small portion of any given
design, and with them come assurances of continuity and ecosystem support. This
support is critical for even ultra-low-cost MCUs in which a “free” RISC-V architecture
might start to look attractive, especially if it can follow through on
processing efficiency.

EP_Viewpoint_RISC-V_custom-ICs

With the RISC-V ISA, SiFive is working to make custom ICs
viable.

 

Still, the 50
paying members of the RISC-V Foundation aren’t newbies to the processing game,
including Google, Hewlett Packard Enterprise, IBM, Nvidia, AMD, and Qualcomm.
They are encouraging the groundswell of support for the RISC-V, particularly
from academia. In fact, the group’s latest workshop was held on the Google campus
in December to packed rooms.

For many, this
groundswell of support is almost like the early days of Linux, and that’s where
RISC-V starts to get interesting: it’s almost got a cult feel to it. At the
head of the cult is David Patterson, who coined the term RISC and set the RISC-V
movement on fire with a 2014 paper on the topic, “Instruction Sets Should Be
Free: The Case For RISC-V” (EECS, August 6, 2014). In the paper, Patterson laid
out the case, including the patent minefield that current architectures
represent, performance compromises, and the comment that even long-standing
companies that may support current ISA architectures do go away in time, giving
DEC as an example.

Of particular
interest, given what’s happening in today’s highly charged security
environment, is the note that a shared open core design would mean,
“…transparency that would make it hard, for example, for government agencies to
add secret trap doors.” That in itself might be enough to fan the flames of the
RISC-V movement.

Still, there’s
another factor: The interest of Google can always be dismissed as yet another
fire into which Google would like to stick a poker — just to see what happens.
But there’s more to it than that. While open-source hardware is a whole lot
more complex than open-source software (à la Linux) — and we know how hard that was
to get off the ground — there is the same level of engineering community
interest in making it happen.

Why? Because
it’s a challenge and a chance to up-end the status quo. Engineers are happy to
devote time, free of charge, just for the chance to be a part of that. With
someone like (now-retired) David Patterson at the helm, that has staying power
— much more than a venture-capital-funded startup with its own closed,
proprietary architecture. It’s going to be an interesting couple of years
ahead.

Reference:https://people.eecs.berkeley.edu/~krste/papers/EECS-2014-146.pdf