XShell and XGS – a minimalist computer

September 24, 2009

I’ve been following Xmos and their great multi core microprocessors for over a year now and a recently listed project recently listed on XMOS community site caught my attention. The XShell (and XGS) project is a minimalist computer with 32M bytes of SDRAM and complete with VGA, keyboard and SD card interfaces. On the software side it offers a simple shell, editor and interpreter making a basic computer system.

Nothing spectacular there you might say, it sounds like a basic DOS PC from the very early 90’s but what is awesome apart from the RAM the entire computer is executed in software on a single microprocessor chip with no dedicate interfaces!

That’s right, only software is used to generate the VGA screen as well as all the other interfaces: keyboard, 1-bit audio, SD card interface and joystick.

  • XShell / XGS Specification

    * Processor: Xmos XS1-L1-128, Single Core, 400 MIPS
    * Memory: SDRAM – 256Mbit, 32M x 8; Serial FLASH – 4Mbit, 512K x 8
    * Display: VGA 640×480 with 256 colours; Text Only
    * Storage: SD Card using FAT16
    * Interfaces: PS2 for keyboard/mouse, Joystick, 1-bit speaker/audio
    * Software: Shell, Text Editor, Simple Language Interpreter

  • One the first things that struck me about this was it would be a great canidate for the $10 computer for developing countries.

    xcores.org goes NTSC

    September 14, 2009

    Yvo of xcores.org has been busy again. His website is showing his progress on a NTSC TV driver with 512 colours.

    NTSC TV Driver

    Heres hoping he can be persuaded to do a PAL TV driver once the NTSC driver is put to bed.

    Xmos XK-1 Development Board

    September 14, 2009

    A new minimal Xmos development board has been found on Letsmakerobots.com


    Its uses the more hand soldering friendly 64-pin XS1-L from Xmos. The XK-1 Board Features:

    * Single XS1-L1 device
    * 400 MIPS
    * Just 50mm x 50mm in size (board)
    * Eight threads
    * 64Kbytes RAM
    * 8Kbytes OTP memory
    * 128Kb SPI FLASH
    * Four user-configurable LEDs and two push-button switches
    * Two 20-way XSYS connectors for XTAG-2 debug adapter and additional XK-1s
    * Two 16-way IDC headers for connecting additional components
    o 24 I/O user expansion
    * Powered direclty from XTAG-2 adapter or external 5V power supply

    and includes a USB based XTAG-2 Debug Adapater.

    Its not yet listed onXmos’s website but I’m sure it’ll be there soon.

    Pocket DSO

    September 7, 2009

    Seeedstudio have been teasing users on the Ardunio forum with advance product news of a really cool pocket DSO.


    The DSO mobile is a pocket size digital storage oscilloscope base on ARM Cortex™-M3 compatible 32 bit platform, equipped with a 320*240 color display, SD card interface, USB connection, chargeable batteries and weighs only 60g!

    If it’s spec is half as good as it looks I know what I want for Christmas.

    September 3, 2009

    Yvo of xcores.org has released his preliminary VDP source code for the Xmos XS1 processor.

    The specs are pretty impressive:

  • 256×192 resolution ( scan doubled in both X and Y )
  • 2 independantly scrollable backgrounds
  • 32 sprites ranging from 8×8 to 64×64 pixels
  • Horizontal- and vertical flipping
  • 16 palettes of 16 colors each, for a total of 256 onscreen out of 32768 colors ( 5:5:5 )
  • 32K VRAM
  • Uses only 2 threads ( VGA and Render )

  • Super Mario vs Xmos

    September 2, 2009

    Yvo Zoer of www.xcores.org has been making the Xmos XS1-G4 multi-core multi-threaded processor do some cool looking things …

    All this on a single chip with no dedicated video graphics controller in sight.

    I hope Yvo releases the source code and hardware details soon, so I can have a fire up my Xmos development board and have some fun.

    Who knows it could snowball into another Uzebox or Xgamestation like community collaboration. Lets hope so.


    September 2, 2009

    The guys (and girls) at Liquidware (of Illuminato Arduino fame) have announced the Illuminato X Machina a small ARM based Arduino like platform that can be interconnected to other X-Machinade to form a cool networked computing cluster.


    Each small square board has its own ARM Cortex M3 microcontroller giving each board its own processor, program memory, data memory and I/O. Each board can also interconnected to other Illuminato+X+Machina boards on one or more of its four sides.

    This idea of parallelism and closely coupled processor interconnection reminds me of the Transputer from the eighties. The concept of the Transputer lives on in the recently founded (in 2005) Xmos and their multi-threaded multi-core processor with integrated interconnection switches.