The next generation - the RISC PC 600 (1994).

After selling over 300,000 first generation ARM machines Acorn announced the second generation machine in time for the May 1994 edition of Acorn User (actually on the 16th of April). The new machine was pitched as a competitor for 486 DX2-based PC's and the recently launched Apple PowerMac machines. It effectively replaced the aging A5000 and was called the Risc PC 600. The development of what eventually became the Risc PC 600 began in May 1992, as the Medusa Project, with 20 full time members of staff.

The Risc PC 600 was powered by a 30 MHz ARM 610 processor. Like the A540, the processor was mounted on a daughter board that plugged in to the motherboard. A unique feature of the Risc PC range was the addition of a second processor slot that was capable of accepting a daughter board holding an "alien" (PC) processor, such as a 486 or 586 chip. The machine could then execute PC programs. This system was referred to as the Open Bus. The two processors shared all system resources. Acorn also redesigned the internal bus and expansion system. The new system, DEBI (for DMA Extended Bus Interface), allowed existing Archimedes/A5000 cards to be used while permiting new cards to use a 32 bit wide data bus (previously the bus width was 16 bits wide) and DMA. The system data bus width was also increased to 32 bits and the processor address space was increased from 4 Kb to 16 Mb, accessed in 4 Kb blocks.

There were numerous other hardware changes. The VIDC was updated, to the VIDC20 and the MEMC and IOC chips were combined, to form the IOMD20. The maximum memory capacity was increased to 256 Mb and two DRAM SIMM slots were provided. The system was able to take up to 2 Mb of VRAM, allowing a display resolution of 1280 by 1024 pixels with 256 colours or 800 by 600 pixels with 16 million colours. Like the A5000 the Risc PC 600 used IDE interfaces, but the drive size were much larger than before, 210 Mb or 420 Mb. An AT keyboard was supplied (earlier Acorn machines featured a slight variant). The usual selection of interfaces were supplied - parallel port, 9-pin serial port, PS/2 mouse, PS/2 keyboard, monitor, headphones and a blank space for a network card expansion that plugged straight in to the motherboard.

The most revolutionary hardware feature, however, was the case. The basic (unexpanded) machine featured three components. The first was the base, which held the motherboard, power supply and interfaces. The second was referred to as a "slice". Each slice was capable to taking one 3.5" drive (floppy drive or hard drive) and one 5.25" drive (floppy drive or CD-ROM drive), along with up to two single-width expansion cards. The third component was the lid of the box, which was positioned on top of the top slice. A maximum of eight slices could be fitted, with up to 4 3.5" drives and 4 5.25" drives. Backplanes could be bought, to allow the use of up to eight single-width cards. The case could be laid flat on the desk or, using four supplied rubber feet, could be stood on its side. The most impressive part was that a screw-less policy was used throughout - the lid and slices were held on with four glass-filled nylon pins and the drives and PCB were held in place with spring clips. The only screws in the case were used to hold on the PSU in place. Padlock slots were provided. The case was designed by the same company who designed the original BBC Micro case.

Possibly the most famous Risc PC was known as "Peter Bondar's Rocketship". This was an eight slice Risc PC, which featured such things as a sink located in the top slice, and a working grill that was used for cooking pizza. (If anyone happens to have a photo of this machine, could they send me a copy?)

The Risc PC innovations did not end with the hardware. The Risc PC was provided with a new version of RISC OS, version 3.5. This came with the 3D Newlook desktop extension, allowing the use of outline fonts on the desktop. The old Palette application was replaced with the Display Manager, which allowed direct setting of the screen resolution and colour depth. The Apps directory, stored in ROM under earlier versions, was instead stored on the hard drive. The memory allocation system was enhanced, the serial and parallel drivers updated and other changes made to support the 32 bit data paths. Acorn Universal Networking software was also included.

The Risc PC was launched in three different formats, and with two different monitor choices. The first model featured one slice, 2 Mb of main memory, no VRAM and a 210 Mb hard drive and cost £1249 with a 14 inch monitor and £1649 with a 17 inch monitor. The second model featured one slice, 4 Mb of main memory, 1 Mb of VRAM and a 210 Mb hard drive and cost £1399 with a 14 inch monitor and £1799 with a 17 inch monitor. The third system featured two slices, 8 Mb of main memory, 1 Mb of VRAM and a 420 Mb hard drive and cost £1699 with a 14 inch monitor and £2099 with a 17 inch monitor. (Prices exclude VAT.)

Next: Enhancements and diversification - Online Media, Risc PC updates and handhelds (1994 to 1996).

Click here to return home or here to return to the Technical History of Acorn.

Robert McMordie

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