website/content/museum/acorn-computer-risc-pc.md

---
title: Acorn Computer Risc PC
categories:
- Computers
types:
- Professional Computer
origins:
- United Kingdom
years:
- '1994'
cpus:
- ARM 610
params:
  name: Risc PC
  image: /media/museum/photos/acorn_riscpc_system_s1.jpg
  company: /companies/acorn-computer
  company_name: Acorn Computer
  specs:
  - label: NAME
    value: Risc PC
  - label: MANUFACTURER
    value: Acorn Computer
  - label: TYPE
    value: Professional Computer
  - label: ORIGIN
    value: United Kingdom
  - label: YEAR
    value: '1994'
  - label: BUILT IN LANGUAGE
    value: BBC Basic
  - label: KEYBOARD
    value: Full 102 Key PS/2 PC style
  - label: CPU
    value: ARM 610
  - label: SPEED
    value: 30 MHz
  - label: CO-PROCESSOR
    value: Choice of IBM-PC CPU’s including 486/586
  - label: RAM
    value: 4 MB (Up to 256 MB)
  - label: ROM
    value: 4 MB containing most of the OS
  - label: GRAPHIC MODES
    value: Numerous - 1280 x 1024 at 256 colours, 800 x 600 16M colours
  - label: COLORS
    value: Full 24bit 16M colours (video memory permiting)
  - label: SOUND
    value: 16bit stereo 8 voice synthesiser (PC sound blaster compatible)
  - label: SIZE / WEIGHT
    value: 35.5 (W) x 38.5 (D) x 12 (H) cm
  - label: I/O PORTS
    value: Parallel, RS232, 2 x PS/2, VGA, 3.5mm sound jack, single width expansion slots (two per ‘slice’)
  - label: BUILT IN MEDIA
    value: 3.5'' floppy disk, 3.5'' IDE hard disk, CD-ROM
  - label: OS
    value: RISC OS 3.5 (mainly in ROM, aditional resources on hard disk)
  - label: POWER SUPPLY
    value: Built-in switching power supply unit
  - label: PRICE
    value: From around £1200
  tabs:
  - photos
  - adverts
  - hardware
  photos:
  - title: LARGE VIEW
    subtitle: ''
    text: The rounded front plastic cover slides inside the machine.
    image: /media/museum/photos/acorn_riscpc_system_s2.jpg
  - title: SIDE VIEW
    subtitle: ''
    text: A nice case design
    image: /media/museum/photos/acorn_riscpc_rightside_s1.jpg
  - title: RISC AND WINDOWS OS'S
    subtitle: ''
    text: The same machine could run alternately RISC OS-3.5 or MS-Dos/Windows OS's thanks to a second Intel processor card.
    image: /media/museum/photos/acorn_riscpc_dualos.jpg
  - title: REAR CONNECTORS
    subtitle: ''
    text: |-
      **(1)** Rsset switch\
      **(2)** Stereo sound output jack\
      **(3)** 15-pin video output plug\
      **(4)** Keyboard mini-Din plug. Any standard PC/AT keyboard can be connected\
      **(5)** Acorn mouse mini-Din plug\
      **(6)** Expansion slots\
      **(7)** Parallel printer DB25 connector\
      **(8)** Serial DB9 connector.
    image: /media/museum/photos/acorn_riscpc_backside_s1.jpg
  - title: 'MAGIC CASE #1'
    subtitle: ''
    text: The base unit and the first 'slice' holding the floppy and CD-ROM drives. Up to eight slices could be stacked to expand the system.
    image: /media/museum/photos/acorn_riscpc_storageunit.jpg
  - title: 'MAGIC CASE #2'
    subtitle: ''
    text: ''
    image: /media/museum/photos/acorn_riscpc_inside_s2.jpg
  - title: 'MAGIC CASE #3'
    subtitle: ''
    text: This working system had 10 slices and an array of gadgets including a working pizza oven and remote controlled sink!!! More detailed information [here](http://www.worldofwibble.com/aboutriscpc.html).
    image: /media/museum/photos/acorn_riscpc_pizza.jpg
  - title: MAIN BOARD
    subtitle: ''
    text: |-
      **(1)** IDE hard disk, here a 1 GB model.\
      **(2)** Floppy disk and hard disk connectors\
      **(3)** IOMD20 - I/O controller and memory manager custom chipset\
      **(4)** Connector of the ARM processor card\
      **(5)** Connector of the Intel/PC processor card\
      **(6)** Floppy disk and hard disk controller chipset\
      **(7)** 256 MB ROM chips holding the RISC OS, here the 3.6 version\
      **(8)** Network card connector\
      **(9)** RAM module connectors\
      **(10)** Video controller custom chipset\
      **(11)** Backplane slot. Early RiscPCs came with the backplane for plugging in Podule cards.
    image: /media/museum/photos/acorn_riscpc_inside.jpg
  - title: PROCESSOR CARDS
    subtitle: ''
    text: The twin processor cards hold the ARM processor and the Intel-PC processor, here an ARM 710 and a Texas Instruments 486DX-4/100.
    image: /media/museum/photos/acorn_riscpc_proccards_s1.jpg
  adverts:
  - title: ADVERTISING PICTURE
    subtitle: ''
    text: ''
    image: /media/museum/pubs/acorn_riscpc_pub_s1.jpg
  hardware:
  - title: ARM 710 PROCESSOR CARD
    subtitle: ''
    text: ''
    image: /media/museum/hardware/acorn_riscpc_arm710card_s1.jpg
  - title: 486 PROCESSOR CARD
    subtitle: ''
    text: ''
    image: /media/museum/hardware/acorn_riscpc_486card_s1.jpg
  comments:
  - author: Douglas Piper
    date: Sunday 29th May 2016
    text: Hi. I use a riscpc600. The canon bjc 2100. Has just died any advice on what I should replace it with. Presumably I can pick something up on ebay
  - author: CLASSIFIED
    date: Friday 20th August 2010
    text: i want one
  - author: Andrew (Glasgow (UK))
    date: Sunday 27th June 2010
    text: |-
      To add my two pence worth and expand on the main article. After the Risc PC 700 released in July 1995 with a 40 Mhz Arm 7 CPU, there was a "Strongarm" Risc PC released in September 1996 with either a 202 or 233 Mhz Digital Strongarm CPU and RISC OS 3.70. Strongarm CPU cards can be fitted in any Risc PC.

      There are also the 233 and 300 Mhz Strongarm-based Kinetic upgrades by Castle Technology which have their own onboard memory augmenting the RAM installd on the motherboard. This goes some way towards reducing the impact of the slow front-side bus.

      Acorn may have long since gone, but the RISC PC appears to be a hardy little beast (or big depending on the number of case slices you have) RISC OS has been developed beyond 3.7, there is now 4.x in ROM which can be softloaded with version 6.20 which is available from Risc OS LTD.

      I have just succeded in getting my RPC on the internet! Of all the retro/old systems I have from its era, the RPC is perhaps the most expandable, and certainly the most versatile.

      Unlike a few years ago there are a few emulators (free and commercial) around for both classic Risc OS and 4.x - current.
  - author: David (Surabaya Indonesia)
    date: Wednesday 8th October 2008
    text: Think about No Emulator? Horewer...
  - author: Tim (UK)
    date: Tuesday 20th June 2006
    text: The notes say "two PS/2" ports. In fact the keyboard was PS/2 but the mouse was a "bus mouse" system in order to keep compatability with the earlier Acorn machines. A Logitech bus-mouse came with the machine.
  - author: Chris (UK)
    date: Monday 24th May 2004
    text: |-
      The first batch of RiscPC 600s did not have 16-bit sound. They required an inexpensive hardware upgrade to support 16-bit sound, and in some cases required a new motherboard because the header (LK14 IIRC) was not present to allow the upgrade.

      In addition, this was not the first Acorn to have a PC card. There are podule cards for the older Acorns, but they were very slow due to the speed of the bus. They also couldn't share memory like the RiscPC one can, so in effect you had to pay for your memory twice.

      The Windows video drivers for the RiscPC even used the ARM to help with rendering the screen. How cool is that?

      It's a huge shame to see the RiscPC turn into a piece of history. Last I checked, there are quite a few going on Ebay. Get yourself a piece of history while you still can!
  oc_id: 1015
  source:
    url: https://web.archive.org/web/20230609185904/http://www.old-computers.com/museum/computer.asp?c=1015
    date: '2023-06-09'
---

In April 1994, Acorn announced the release of the second generation of ARM machines – the Acorn RISC PC 600. Code named the **Medusa** project, this was set to replace the then ailing flagship [A5000](/museum/acorn-computer-archimedes-a5000/) machine.

As the name suggests, one of the main features of this computer was that it could run both Acorn and IBM-PC software side by side. This was achieved by a second CPU slot that could accept a daughter board with a PC CPU, such as a 486 or 586. This second processor then had shared access with the primary CPU to all the system resources. No more CPU intensive software PC emulation required!

As well as the second processor, other major enhancements included an updated video controller with the option for dedicated video RAM. The graphics chip in previous Archimedes range machines had shared the system memory with the rest of the computer which often proved to be a bottle neck without true DMA. Now the video controller could have video memory of it’s own, removing the bottle neck.

The system data bus was doubled in size to 32bits wide, and the MEMU and IOC chips were combined to create the IOMD20. This resulted in much better overall I/O, yet another bottle neck removed from previous machines. The system memory was also upgraded to a maximum of 256MB and the memory bus was designed to use the more widely available EDO SIMM’s.

A unique feature of the RISC PC was its case. This came in the form of the base holding the motherboard and power supply, a mid section for mounting one 3.5" device, one 5.25" device and two single width expansion cards, and then a lid. The magic was that you could add up to 8 slices at any time, giving you a very easily expandable computer, and all held together with clips and springs negating the need for a screwdriver. Very neat.

There were 2 other Acorn RISC PC's. The RISC **PC 700** was released July 1995 and the RISC **PC-2** was much publicised by Acorn and then dramatically cancelled at the last minute.

Thanks to **Paul Hadfield** for his kind help.