The supplied printed manual was better than I expected, especially as Bottom Line is new to the CPU card business. The manual even included a compatibility section, listing the known issues with PowerForce design CPU upgrades (Adaptec U/W SCSI cards, Media 100 and Avid Video capture cards), and listed suggested alternatives to these products, a nice touch. The first printing I received consisted of 18 pages including the warranty statement (2 years).

There were photos illustrated guides to installations in the the 73/75/7600, 85/9500 and 86/9600 system. Bottom Line tells me they are working on a volume II that would list Power Computing and Umax systems as well. Installation precautions and a troubleshooting section, and a list of switch/speed settings were also included. I think the documentation was suprisingly good and I detected no errors in the switch setting tables for the speeds I used. I did note that the pages were not numbered, a minor flaw. [Update - on 5/6/99 a reader reports the lastest manuals are not the same as the first printing I had.]

Installation was of course identical to other CPU cards and only took a minute or so. In most cases (especially with Apple macs) - you may have to remove the L2 cache dimm. I've seen some upgrades at seem to work better with it installed _if_ it's a power computing cache (they made very fast cache dimms, unlike most apple models) - but I'd guess 90% of G3 upgrade problems are due to L2 cache dimms

As with all adjustable speed cards, most of the initial effort will be adjusting the speed of the card and finding the maximum reliable speed. If you're not the tweaker type - just set the switches to 250 Mhz rated speed (A=6, B=5) and use the 1.5:1 extension. If you want to get the maximum performance out of the card, then additional testing and trial and error will be required.

Although I rarely follow this advice, it's always best to back up your data before boldly going where no man had gone before. There are no guarantees of success, so exercise common sense and precaution (backup data, start low, verify, move up slowly).

Speed Adjustments:
The CPU speed of the card is set by two small rotary hexadecimal (0-F) switches on the back of the card, mounted at a right angle so that they are accessible when the card is installed in the system. You can leave the card set to its default CPU speed of 250 Mhz or you can try and run faster speeds by adjusting the two switches to the desired speed according to the table in the manual. Of course you adjust the switches with the power off.

Verify Reliability!
When running the card above the rated speed, always verify reliable operation at the new speed by running with CPU intensive applications for many hours. If there are any errors or failures, reduce the speed setting to a lower one as shown in the manual speed table. When errors are seen I like to reduce speeds by at least two clicks backwards to ensure I'm not running the card on the "ragged edge".

Use common sense, always start low and work up, not the other way around, which can be a disaster leading to frustration at best, and corrupted files at worst. It is foolish to have the fastest machine around if it crashes every other hour. Speed without reliability is nothing, but you don't have to sacrifice one for the other if you are careful, use quality components and spend a little time up-front in setup and testing.

To verify that 300/300 was reliable, I ran Newer's RAMometer continuously for 24 straight hours with the cover on, and saw zero errors.

The PowerTower Pro, like most PowerComputing models, does have a fan blowing on the CPU heatsink at all times. That could be a factor but considering how relatively cool the G3 CPU cards generally run I doubt it is much of a factor.

Below is a photo of a G3 CPU card installed in the PowerTower Pro. Although it's a close fit with the PTP CPU bracket/fan assembly, I could still adjust the switches with the card installed.

Speed Adjustment Switches (PowerTower Pro installation shown)

I've gotten feedback from a PowerCenter owner that the plastic fan/cpu bracket touches the switches on all PowerForce (PowerLogix, XLR8, Mactell, Bottom Line) design cards, and that some trimming may be required. I checked for this in my PowerCenter Pro, and did not have this problem, but did note that one of the speed adjustment switches could not be reached with the CPU fan/bracket installed (click here for a photo showing this). CPU speed adjustments would require removing the fan/bracket (just a few seconds) to provide access to the 2nd switch.

Installation was no more difficult than any CPU card, but if you want to explore accelerated speeds, count on spending some time up front to verify that settings you choose are really reliable. With Mactell's preferred list of settings, and the lack of a variable cache speed control you will likely spend less time than other similar cards however.

Documentation was adequate, but owners with no experience inside their Macs may wish for a few photos of the procedure. The manual did have clear explanations of the speed settings, a list of preferred settings and a troubleshooting section.

Overall I rated documentation a 9.

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