PowerLogix Downclocking Upgrade Cards?


Using a magnifying glass, and presumably some tweezers, MacBidouille may have established that some PowerLogix upgrade cards are using downclocked processors.

Looking at a PowerLogix DP 800 card, the CPU is labelled XPC7455RX867PC, and as designated, it's built to run at 867MHz. As it turns out this is not unusual and there's nothing inherently wrong with this; CPUs have 'safe' operating speeds; depending on the CPU and bus speed, meaning some can run much faster than the clock with which they are labelled. It's not unusual, for instance, for a bunch of IBM PowerPC G3 processors, rated at, say, 300MHz, to be run at 400MHz. 300 may simply be the label for the machines they were slated for.

Apple has also done this with its current range of Power Mac towers; hardware hackers have successfully overclocked 867MHz machines to 1GHz, and 1GHz to...more than that. Some have even claimed to have the 1.25GHz DP Power Macs running (unstably( at 1.5GHz.

[Update]

Powerlogix has stated to IGM that the reasoning for this is to accommodate a Mac with a 100 MHz system, presumably what MacBidouille was using for their tests. Powerlogix stated that the processor could only run at 8:1 or 9:1 bus ratios, or 800 MHz or 900 MHz. Not designed to run past 867 MHz, the CPU was was clocked down to 800 MHz.

Also, Powerlogix notes that if one were tempted to try overclocking the upgrade to 900 MHz, it would require soldering on the card and would void the warranty.