It began in November 1996 when Acorn decided that it was time to take advantage of the dramatic improvements in component and peripheral technology that had taken place since the production iof the original Risc PC. The task ahead therefore meant that the design team had to encompass this technology, build on the strengths of the existing product and eliminate its weaknesses.
The starting point The success of the Risc PC was based on a number of key strengths. For example, the Risc PC was a very expandable design, incorporating a removable processor card which made it extremely easy to upgrade. The machine provided PC compatibility which was a popular addition over earlier Archimedes machines. And the Risc PC offered excellent video and audio performance, along with a much enhanced version of the highly efficient Acorn operating system, RISC OS.
Weaknesses in the product range came to light over time however. Memory architecture, speed and I/O were not up to modern standards in terms of performance, and there were difficulties arising from the fact that expansion was non-industry standard.
The starting point for the development team was to incorporate the strengths of the Risc PC and overcome the weaknesses in the new product.
Their goal was harness the full potential of the StrongARM processor, support multiple processors, provide PCI support and update the I/O. In addition, they needed to retain podule support, provide the best possible graphics performance and enhance RISC OS functionality. All of this would be achieved by taking full advantage of the latest technology and peripheral developments.
In addition, the new machine had to run existing RISC OS applications.
The original idea was also to fit all of this into the existing Risc PC case design, but this proved to be one hurdle which the development team just couldn't clear.
The Case Whilst the new motherboard fitted onto the footprint of the existing Risc PC, the PCI cards proved a real problem. Just fitting them would have been difficult, but with a power requirement of 31W per card coupled with new EU directives on fifth harmonic distortion (calling for extra filtering on the PSU), the decision was finally made to move towards an entirely new case design and power supply.
The new case design was a radical change from that previously used, it being the first ever Acorn tower case. We decided to go one step further and made the front panel yellow, ensuring that the new Risc PC would be as distinctive in visual terms as it would be in performance.
The new striking case design builds on the good points of the existing Risc PC design. It encompasses the removable processor card, enables new peripherals to be added easily and provides internal access without the need for a screwdriver. One of the key improvements is a motherboard that simply slides in and out!
System Architecture In order to meet the design objectives of the project, much work was required. IOMD needed to be completely redesigned in order to give a high speed I/O world and multiple bus mastering.
VIDC20 needed to be improved to give bigger and better screen modes. A PCI bridge was needed to enable industry standard expansion.
As well as these, other improvements included a Codec for better standard audio support, a new IDE interface allowing 4 enhanced IDE drives and still keep the podule interface for backwards compatibility.
In supporting all these new features the main memory was revised to synchronous DRAM, VRAM was improved to EDO VRAM and expanded to 4 Meg. An extra serial port, joysticks, IrDA and MIDI were added to give a fully specified, high performance machine.
ASIC Development At the heart of the whole machine lies the new I/O and memory controller chip, IOMD2. This one device has to perform hundreds of different tasks for the machine to function effectively. To ensure this performance, the development team rigorously modelled and tested the design in a giant FPGA.
Features of IOMD2 include a much enhanced 64 Mhz bus performance, a multiple bus mastering system and message passing for multiple processors. (Production silicon is expected into Acorn in early September when final benchmarking can take place).
To drive the video performance whilst retaining compatibility with existing software, the current VIDC 20 chip geometry has been shrunk to give a 100% performance improvement.
Updating RISC OS The starting point for updating RISC OS was not only identifying the modifications required to support the new hardware, but also identifying improvements that needed to be made.
Lack of support for long file names and large directories had been problems for too long and had to be remedied. !Boot had become too complex and a vastly improved method of configuring the system and applications was required. The general look and feel also needed updating but without throwing away the many excellent existing features.
One of the most visible areas for improvement was the icons. Having tried out various different sets throughout the course of the project, it was agreed that the original Risc OS ones tended to look better. So these were improved and extended.
Why Phoebe? Choosing the right name for the new machine was absolutely crucial. It needed to be something obvious and logical that clearly stated what the product was. And it also needed to be memorable and different, in keeping with both the unusual look of the product as well as Acorn's reputation for individuality.
So we've chosen to go with: Phoebe Risc PC 2.
The Acorn enthusiasts' group, the Clan, were invited to submit their ideas for names earlier this year. One of the most popular was Risc PC 2 which was simply incorporated into the project name, Phoebe, by Acorn's advertising agency who designed the logo for the new machine. consensus..
What next? Slow prototype machines have been previewed at special events around UK and Europe since earlier this year. In an unprecedented act of support from our customers, Acorn has back orders for hundreds of units based on these protoype machines.
Acorn is hoping to have the first, fully functioning units on show at Acorn World '98 in October, with full production units available shortly after the show.
Acorn will spend over £2million on the Phoebe project. We hope you think it was worth it. We do!