The XLR8 266/177 CPU card contains a IBM or Motorola 266 Mhz PowerPC 750 CPU and 1 MB of backside cache. The card did not appear to have as many circuit layers as some cards I've seen (judging from the thickness of the printed wiring board [pwb]), but reliability was good during testing.

Quality of workmanship was very good, with no cold solder joints seen and no jumper wires or other modifications visible that would indicate a design change after the pwb was manufactured. The heat sink made good contact with the CPU, and there was thermal compound between it and the CPU. The card ran remarkably cool during the tests - even at very high CPU speeds for extended periods of time. The CPU fan in the PowerTower Pro helps I'm sure, but I still feel this is a much cooler running card that many G3's I've tested.

Note: The speeds documented here are for test purposes only and not a recommendation to others to overclock their card. XLR8 is said to honor the warrany regardless of the speeds run but verify that before you attempt settings over the rated CPU speed, Overclocking is risky and can result in loss of data or hardware failures.

Based on my experience running this particular card far beyond it's rated CPU and cache speeds, I feel the card is well designed with more than adequate "headroom". However I do not recommend others overclock the card as it will void the warranty. The issue of cache sensitivity could possibly be a problem for owners of machines with non-removable cache (9500, 9600/200 and 9600/233, UMax S900) but XLR8 says they have no reports of problems from 9500 owners. [Update: The XLR8 G3/266 ran fine in the 9500 motherboard based Genesis machine, at the same speeds as in the PowerTower Pro used for this review] As a general rule, I recommend removing your L2 cache when using any G3 CPU card, based on my experience with most of the models on the market.

As a side note, when I called posing as a befuddled customer I was on hold for less than 2 minutes. My experience with their tech support has always been positive. Based on feedback I've gotten in the last year they stand behind the product should you ever need assistance.

Examination of the card (done to ensure I'm not sent a "ringer") verified that it contained a 266mhz Motorola PowerPC 750 CPU and 1 MB of 5ns IBM Cache (2 chips) (click here for 79k JPG image closeup).

Update: In January 1999, XLR8 released a new V1.2 of their Cache Control software that reportedly solves the compatibility issues with Adaptec SCSI cards and Retrospect backup software. Updates are available at: http://www.xlr8.com/support/files.html.

Since this card is based on the PowerForce design, I expect it also has the same incompatibility with the Adaptec PCI SCSI cards. I've not verified that personally however. I've had success using the PowerForce design with most other PCI SCSI cards on the market such as the ATTO Express PCI, Initio Miles, and HammerStorage JackHammer. For a comparison of all the popular PCI SCSI cards for the Mac, see the SCSI section of the site's reviews/features page.

Other compatility issues: The Matrox Millennium video card drivers, Media 100 capture cards, and Dantz Retrospect backup software are also said to be incompatible with the Powerforce design CPU cards (based on personal tests and reader feedback)

XLR8 lists this card as compatible with the following Mac models:

• Apple PowerMac 7300, 7500, 7600, 8500, 8600, 9500, 9600
• Power Computing-PowerWave, PowerCurve, PowerCenter, PowerCenter Pro, PowerTower, and PowerTower Pro.
• UMAX Supermac S900, J700

The hardware design seemed solid in use, with great adjustability and my sample was capable of reliable operation above the rated speeds (not recommended to others as it will void the warranty). For this reason I rated the hardware features/design a 9.

At first I wished for a remote control for speed settings, but the more I thought about the ribbon cable I decided it may be preferable to have the switches on the card, since they were still accessable when the card is installed. Although unlikely, a ribbon cable has potential for damage, adds clutter and is another thing to block airflow inside the case.

The next page contains a summary and final comments on the product and company.