Open source processors
An open hardware revolution is on its way and it’s coming to conquer your processors, as Neil Mohr reveals…
An open hardware revolution is on its way and it’s coming to conquer your processors, as Neil Mohr reveals…
Monopolies aren’t all bad. At least, they don’t have to be. But with a single corporation owning the rights to the x86 instruction set, the consumer processor market is hardly abuzz with competition. It’s true enough that AMD’S star is on the ascent, but that’s been helped by a decade of stagnation by Intel, ever since the heights of the original Core 2 releases.
The situation is an indication, though, of what would happen if x86’s only competitor dropped out of the processor market: Intel could stop all development and you’d still have no option but to buy its processors.
It isn’t healthy to overspecialise. “But there’s Arm!” you rightly cry. Arm is a peddler of intellectual property, though. The company licenses its design and manufactures nothing itself. It’s a healthier arrangement than that of Intel and AMD –there’s a range of competition, big and small – but the licence fees are far from trivial.
Of course, this is hardware we’re talking about. People can’t just give it away for free, like software…. or can they? Just as the opensource Linux kernel has ultimately triumphed over all other competitors (in many areas, anyway), it’s now the turn of open hardware to have its day.
So, how is this revolution going to happen? What devices are we going to see powered by open hardware? And when is this change going to occur? To answer these questions in a meaningful way, we’re first going to have to delve into what makes a processor tick, before considering what’s actually needed in this day and age of the Internet of Things…
Ones and zeros. At their heart, processors are pretty simple engines. So simple, in fact, that you can recreate one inside Minecraft (http://lazcraft.info/tagged/cpu). There are registers to store instructions, data and results. There’s a program counter that moves everything along to the beat of the processor clock. A control unit decodes fetched instructions, shifts data and co-ordinates the pipelines that execute individual instructions. Bolt on a cache and memory, and you’re pretty much there. We’ve designed a processor – now, where’s our money?
The element that really defines this architecture is the instruction set: the ISA (instruction set architecture). As you might imagine, this can get complicated. The original design philosophy, if you can call it that, for processor instructions is known as a Complex Instruction Set Computer, or CISC. We’re being dismissive, because when x86 was being devised, instructions were chosen and added as needed, building on top of the 1972 eight-bit 8008, but really starting with the 1978 8086 and onward.
Out of a project at the University of California, Berkeley, the reduced instruction set computer (RISC), philosophy was created between 1980 and 1984. The realisation was that compiled Unix used only a third of the available CISC instructions. The obvious move was to concentrate design efforts on those few instructions, to make them run as fast as possible.
The reduction in complexity was astounding: The RISC II architecture from Berkeley was implemented with 39,000 transistors; the CISC Motorola 68000 produced around the same time, and which powered the Amiga 500, used 68,000, but the RISC II design ran up to 420 per cent faster. The Intel 80286 that was also manufactured around that time used 134,000 transistors, and ran far slower than either.
The interesting part of this period of computing history is that while consumer PCS consolidated around Intel’s x86, the high-performance computing market fell in love with RISC designs. SUN Sparc was the industry leader, but there was DEC Alpha, IBM Power, and MIPS (these last two are still going), to mention just the leaders at the time. So while, in 1992, Intel had its 486DX2 at 66MHZ managing 25MIPS, Alpha had its 150MHZ 21064 pumping out 86MIPS, and the confusingly named MIPS had its 150MHZ R4400 managing 85MIPS.
We should also mention an obscure
UK outfit called Acorn Computers, which at the time (1981–1994) was manufacturing the BBC (as in the