RISC World

The MicroDigital Omega

Dave Holden tells us what he has been doing on his holidays

I had to drive all the way from London to York to collect a van load of RiscPCs and monitors from yet another school that was going PC. This was the Monday of 'Wakefield Week' and I had ordered some IDE interfaces from Baildon Electronics who manufacture the APDL ARCIN and Blitz interfaces and who share premises with and are closely associated with MicroDigital. Now knowing how very busy everyone was working on the Omega I was a bit worried that my stuff might get forgotten, so I phoned a few days before to say I was coming up to York and would pop over to Saltaire and collect them on the way back if I had time (not a huge detour after a 250 mile trip).

At about 11 o'clcock I arrived at the MicroDigital workshops. David Atkins opened the door and was somewhat surprised to see me. Unfortunately it seemed that Dave Prosser, the MicroDigital technical director, had been so busy working on the Omega he had completely forgotten I was coming and so hadn't got my IDE interfaces ready (they were eventually delivered to the show venue, Thorpe Park Stadium in Wakefield, just before the show). Anyway, I was invited in and offered a cup of coffee, and the talk naturally turned to the Omega.

'We've got it running upstairs' he said, 'come and have a look if you've got time'.

The long drive back down the M1 was rapidly losing its attraction.

What I saw was obviously not a pretty box, although the case pictured on the MicroDigital web site was there - and extremely neat it looked, too. It was, as you would expect, a bare PCB sitting on the bench with hard drive, power supply, monitor and keyboard and mouse plugged in, plus a few connections to test instruments. The first thing that struck me was how small and bare it looked. The PCB is a small ATX format, even smaller than the Mico motherboard, and there are surprisingly few 'bits' on it.

Now if there's anyone silly enough to believe that a PCB with assorted parts dangling off it isn't a 'computer' then all I can say is that, because it's a standard ATX form PCB, in about ten minutes I could have had it all fitted into a PC case and looking fit for anything with the aid of nothing more sophisticated than a screwdriver.

David Atkins had disappeared for a while, and when he returned it was with a hard drive containing a copy of the latest version of Cerilica's Vantage. Now this is a fairly complex program, one which taxes current hardware, so it was obviously going to be a good test of the Omega. Vantage was copied onto the Omega's hard drive and worked straight away - no problems.

Vantage on the Omega (note the Task Manager display)

While I was there we tried a number of other programs, and the only one which gave any trouble was Artworks. However, this wasn't really surprising as it was an old version, copied from David Atkins' backup hard drive, and the Omega had 768 megabytes of RAM. As most people will be aware Artworks gets a bit upset on systems with more than 64 Mb, so this much RAM must have come as something of a shock to it. I gather that Martin Weurther's patch for this problem has now been applied and Artworks is working OK.

Since it was revealed that I'd actually seen an Omega the main question I've been asked is 'how fast is it?'. The fact is, I hardly noticed the speed. What I found impressive was the small size of the PCB and the fact that I was actually seeing a working Omega at last. That doesn't mean that it wasn't impressively quick, it was certainly noticeably faster than my own 300 Mhz RiscPC. Dragging a window over a Draw window containing a large 24 bpp JPEG produced almost no delay in redrawing, which is not the case with my own machine, and Vantage certainly seemed to be flying.

However, to be perfectly honest it seemed to me at the time (and still does) that speed at this stage is the least important thing. What is really important is that this completely new design was working, and for the first time there is a RISC OS computer that has absolutely no dependency on Acorn technology. Not only that, but it's going to get even better, and it's this aspect of the design that interests me.

Although quite a bit of information about the Omega has been published a lot of people still haven't fully grasped the implications of the technology used.

Conventional computers use a series of circuit 'building blocks' as well as the CPU, input/output chips, etc. With RISC OS machines this has had to be the proprietary Acorn IOMD, VIDC and MEMC chips, because they are all that current versions of RISC OS can understand and work with. It is partly the limitations of these which restricts the performance of present machines, especially the 7500FE powered models because in these the functionality of the proprietary chips is built into the CPU, and it is the requirement for these devices which makes porting RISC OS to 'foreign' hardware so difficult.

The base model Omega uses a 300 Mhz Intel Strong ARM processor and the normal Southbridge 'Super Combo' chip. The Acorn MEMC and VIDC are replaced by the MicroDigital Lightning© chipset and the standard Northbridge chip is replaced by a special MicroDigital designed version on an FPGA. Similarly the System chip is a CPLG device. As you can see, the main feature of this design is that instead of the usual interfacing logic most of the work is done by Complex programmable Logic Devices (CPLG) or Field Programmable Gate Arrays (FPGA) CPLDs and FPGAs can be considered as a sort of 'raw' circuit block. They may contains hundreds of thousands of semiconductor devices, but these are not naturally connected up to form electronic circuitry but can be 'programmed'. What we have here is therefore a reprogrammable computer or what MicroDigital refer to as a soft computer. Now I know all computers can be reprogrammed, and even ROM based OS's like RISC OS can be put in flash ROM, but this is not software programming but programming the hardware. Instead of just writing programs and operating systems it is now possible to 'write' hardware.

The Omega motherboard

A major advantage of using a CPLDs and FPGAs is that you are not restricted to 'off the shelf' components but can design your own without the need to commit to purchasing tens of thousands of units. Not only this, but because it is a Field Programmable device it can be reprogrammed in situ so the design can continue to develop and upgrades can be supplied to users without the need to make yet more expensive chips and replace the old ones. So the cost of a 'hardware upgrade' is very much reduced.

The machine I saw was a perfectly stable RISC OS computer running RISC OS 4.03 'out of the box', exactly as used in the Mico. It can do this because the Lightning chipset is programmed so, to the OS, it has the 'look and feel' of Acorn hardware although in fact it is very different. It was at least as quick as the fastest machine currently available, and that's being very conservative because I didn't run any speed tests at the time and don't want to run the risk of saying 'twice as fast' or 'four times as fast' without figures to back it up.

Obviously things like video and hard drive performance are vastly superior to a normal RiscPC, with screen displays of up to 1200 x 1600 in 24 bit colour, and almost certainly more to come. I don't have any statistics for hard drive performance because even the fastest hard drive Microdigital had available wasn't quick enough to test the system to its limits, but as soon as they fit a faster model they'll run some tests. Furthermore I discovered later that the machine I had been using was running a test version of the Northbridge chip while various modifications were made, and that this was considerably slower than the later version, so I wasn't seeing it at its best! Possibly by the time this article appears there will be some figures available on the MicroDigital web site.

Running 1600x1200 in 24 bit colour

The X-Scale processor is fitted directly to the motherboard on the prototypes, but production machines will have a socket to take a small 'daughter board'. At present the intention is that this will be able to carry either the X-Scale processor, a floating point unit, or both. Obviously if even faster and more powerful ARM processors become available then there is the possibility of these being offered as well.

I did ask David Prosser to explain exactly about the ArmTwister© technology is and how it is used to switch between the SA110 and X-Scale processors. This is an extremely complex system, and with the benefit of hindsight I should have made notes and taken a little more trouble to understand the details. Since I didn't I shall not go into it for fear of getting it wrong, but hopefully David will be able to write about it himself sometime soon.

"How does ArmTwister work then?"

MicroDigital will very shortly decide that the machine is advanced enough for them to produce the first production batch. But development won't end at that point. There are still lots of developments that can be incorporated, and thanks to the technology used these improvements will be available to anyone without the need for costly conventional hardware upgrades. Instead of having to pay for hardware it will be possible to download an upgrade from their web site and reprogram your computer's hardware to give improved performance and facilities.

This means that the Omega is not a fixed design. Rather as the RiscPC has evolved so will the Omega evolve. The current Omega is in the same position in its development cycle as the first RiscPC. Think how far that has come from the first model with its 610 processor and 1Mb VRAM to a 300 Mhz Kinetic with Viewfinder graphics card and consider how much potential the Omega could have since it has the ability to produce a similar performance increase, especially when the X-Scale processor is fitted.

Furthermore there is great potential for variations on this design. The Omega is not 'just another computer', it's not even really a RISC OS computer, it's a new type of computer. The fact that the first incarnation to see the light of day will be a RISC OS desktop machine is a huge bonus for all enthusiasts, but the technology can be applied to many different purposes. From the point of view of RISC OS enthusiasts this should mean that, as MicroDigital's expertise in working with this technology grows, we will reap some of the benefits, and these will hopefully come in the form of performance enhancing upgrades to the hardware at little or no cost.

Unlike the RiscPC or Phoebe the Omega is not the end product of a development process, it's just the first step on a rather tall ladder.

Dave Holden