Product Reviews

It's human nature never to be satisfied, so a Mac which seemed fast when you bought it now appears to crawl along. Hope, however, has appeared in the form of the PowerEdge, and its latest releases for various CPU-upgradeable machines.

We tested a 200MHz 604e-based card in a standard 100MHz 601-based Power Mac 7500. The high-speed 604e processor used an industrial-strength heat sink almost the size of the whole card, as opposed to the 601's small metal frills. The upgrade we saw was a pre-production model and had a few minor stability problems, but these shouldn't appear in the commercial version.

Installing the board was simple. We pulled the original CPU straight out of its slot, pushed the new card firmly into place, replaced the Mac's lid and switched the power on. We were then faced with a souped-up Mac which ran at a full 200MHz and had all the muscle of a 604 PowerPC processor. As this is a complete CPU swap, there should be no strange compatibility problems, and the original Apple warranty is still valid.

Certain conditions will upset a CPU upgrade such as this; RAM slower than the Mac's recommended rating becomes more of an issue, and can affect the level of acceleration achieved. Some Level 2 caches, including certain types from Apple, can cause stability problems. Acceleration can also be hampered by the inefficient design of some boards. But XLR8

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manufactures an 'acceleration certified' Level 2 board which is supposed to resolve these problems.

We ran a number of benchmarking utilities which report details of the CPU's type and performance, and they all assured us it was indeed a real 200MHz 604 processor. We also used the industry standard Speedometer utility to compare the new performance with a standard 7500/100, and the difference was remarkable. The CPU was rated at around 2.5 times faster, while its raw maths speed was three times better. We used standard VRAM to drive the monitor in the 7500, and video re-draw proved to be almost twice as fast.

Testing a 10Mb Photoshop file involved applying a 10 pixel Gaussian blur. While 10Mb isn't particularly large, it involves a fair amount of processor-intensive calculations, and so is a fair test of the CPU's capabilities.

On a non-accelerated Power Mac 7500 this took an average of 37 seconds, but on the PowerEdge-enhanced 7500 it took just 18 seconds. QuickTime grabbing and processing was similarly enhanced.

It is easy to get used to a high-speed Mac, and what made the difference more real was having to go back to the unaccelerated CPU after the review.

XLR8 manufactures cards at a number of different speeds, from 180MHz up to 275MHz, as well as various dual-processor versions.

The company is undoubtedly working on even faster CPUs, but the speed limitations of Apple's current motherboard design will become a problem.

The 200MHz board should be available now, and costs around £649. This will bring any Mac with a compatible CPU slot up to the cutting edge of processor speeds for around a quarter of the price of a full 200MHz machine.

Apple's 120MHz and 133MHz upgrade cards have, not surprisingly, now been discontinued, and successors aren't yet available. With a reasonable price, excellent speed and no compatibility problems, the XLR8 card appears to be the best CPU upgrade available.