RISC, Tagged Memory, and Minion Cores

Buy a computing device nowadays, and you’re probably getting something that knows x86 or an ARM. There’s more than one architecture out there for general purpose computing with dual-core MIPS boards available and some very strange silicon that’s making its way into dev boards. lowRISC is the latest endeavour from a few notable silicon designers, able to run Linux ‘well’ and adding a few novel security features that haven’t yet been put together this way before.

There are two interesting features that make the lowRISC notable. The first is tagged memory. This has been used before in older, weirder computers as a sort of metadata for memory. Basically, a few bits of each memory address tag each memory address as executable/non-executable, serve as memory watchpoints, garbage collection, and a lock on every word. New instructions are added to the ISA, allowing these tags to be manipulated, watched, and monitored to prevent the most common single security problem: buffer overflows. It’s an extremely interesting application of tagged memory, and something that isn’t really found in a modern architecture.

The second neat feature of the lowRISC are the minions. These are programmable devices tied to the processor’s I/O that work a lot like a Zynq SOC or the PRU inside the BeagleBone. Basically, they’re used for programmable I/O, implementing SPI/I2C/I2S/SDIO in software, offloading work from the main core, and devices that require very precise timing.

The current goal of the lowRISC team is to develop the hardware on an FPGA, releasing some beta silicon in a year’s time. The first complete chip will be an embedded SOC, hopefully release sometime around late 2016 or early 2017. The ultimate goal is an SOC with a GPU that would be used in mobile phones, set-top boxes, and Raspi and BeagleBone-like dev boards. There are enough people on the team, including [Robert Mullins] and [Alex Bradbury] of the University of Cambridge and the Raspberry Pi, researchers at UC Berkeley, and [Bunnie Huang].

It’s a project still in its infancy, but the features these people are going after are very interesting, and something that just isn’t being done with other platforms.

[Alex Bardbury] gave a talk on lowRISC at ORConf last October. You can check out the presentation here.

Raspberry Pi gets RISC OS, can now play Elite

The processor in the Raspberry Pi – an ARM11 built by Broadcom – actually has a long and storied history. Much as how the Intel i7 in a top-of-the-line desktop can still run code written for the original IBM PC, the ARM chip in the Raspberry Pi is also based on decades-old technology.

The first ARM-based computer was the Acorn Archimedes, a mid-80s computer with 512kB of RAM and no hard drive. The Archimedes ran RISC OS, a very nice graphical operating system written explicitly for the ARM architecture. RISC OS is now available for the Raspberry Pi, finally bridging the gap between educational computers from 1987 and 2012.

Of course, a very much updated version of 25-year-old operating system running on a Raspberry Pi doesn’t mean much without a ‘killer app,’ does it? For the original Acorn Archimedes the killer app – and one of the best video games of the 80s – was Elite, a space trading and combat game that featured vector-style ships. [Pete Taylor] downloaded the Raspi RISC OS image and got Elite running using an Archimedes emulator and, of course, the Archimedes port of Elite.

It’s a pretty neat development if you’re in to alternative OSes and one of the best space-based games ever made. Well worth a download, at the very least.

Retrotechtacular: Introducing the brand new Acorn Risc Machine

Get ready to be swept off your feet by this Acorn Risc Machine promotional video from the Mid-1980’s (also embedded after the jump). We’re sure most have put it together by now, but for those slower readers, this is the introduction of ARM processors.

The video has a bit of everything. There’s a deadpan narration with just a bit of British accent around the edges. But that’s spiced up considerably by the up-beat synthesizer track playing in the background. You’ll see plenty of programmers in short-sleeve dress shirts, and we challenge you to count the number of mustaches that make it on camera. But jest aside, it’s fun to think of how the advent of this chip affected the world.

This post is just the second installment of our Retrotechtacular series (here’s the inaugural post). We haven’t seen any old movies come in from readers yet. What are you waiting for? Digitize that footage because we want to see it! Of course it doesn’t have to be your own movies, so anything you come across that covers decades-old tech is fair game.

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