Further UNIX developments - The R260 and R226 workstations (1990).

In mid 1990, Acorn expanded the range of machines running RISC iX. The existing R140 was supplemented with the R260 and R225 machines.

Both the new machines were functionally identical to the later A540 model. The R260 was fitted with 8 Mb of RAM and a 100 Mb SCSI hard disc drive as standard, while the R225 came with 4 Mb of RAM and no hard drive, and was intended as a cheap networked UNIX station. Both machines were supplied with new ARM3 chips and built-in Ethernet interfaces.

I have been unable to find out much about the R260 and R225. If anyone can tell me anything about these machines, please e-mail me using the link at the bottom of the page.

Following on from the R260 and R225 UNIX machines, Acorn released a new high end RISC OS based machine towards the end of 1990. This machine was called the A540.

Externally the A540 was virtually identical to the A4xx/1 range, the only differences being that the keyboard had no function key strip, and there were a number of extra connections on the back of the machine. The main differences were internal. First the A540 was supplied with an ARM3 chip, clocked at 33 MHz. Second, the memory was clocked at 12 MHz, rather than the 8 MHz of earlier machines. Although there were faster ARM3 upgrades available, the A540 was faster than an upgraded A3000 or A4xx/1 because faster memory clock.

Inside the case, the A540 was substantially different to the A4xx/1 range. The motherboard was fitted with the MEMC, IOC and VIDC chips, along with 4 Mb of memory and a series of four sockets. One of these was designed to take a daughter board holding an ARM processor, while the other three were capable of holding memory expansion boards, each containing up to 4 Mb of memory and an additional MEMC chip to allow the A540 to access it. The machine was fitted with an Acorn SCSI card and a 100 Mb SCSI hard drive, making the A540 the only RISC OS machine to be provided with SCSI by default rather than ST506 or IDE. The video display hardware was also updated, to support both standard VGA and super VGA monitors (with resolutions of up to 800 by 600 pixels). Finally, there were a number of minor updates to RISC OS to allow it to cope with up to 16 Mb of memory.

The A540 was intended to be the high-end Acorn model, and, as such, had a high-end price - the base model, without a monitor, cost £3500, while a model with a monitor, typically a Taxan multisync, cost nearly £4000. It was the undisputed top of the range Archimedes until September 1991, when the next Acorn computer was launched - the A5000.

Next: The next revolution - The A5000 (1991).

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Robert McMordie

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