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Q:  I'm having errors or freezes with a PL BlueChip PB G3 CPU Upgrade:

A:  In my January 2001 review of the PowerLogix BlueChip G3/500 CPU Upgrade I noted the (used) review loaner sample had problems running at the default 250Mhz cache speed. I used Powerlogix's Cache Profiler to set the cache speed to 200MHz (5/2 ratio) which solved these problems. The upgrade was 100% reliable in a week of constant testing after lowering the cache speed, where before it would error out in many extended tests at the 250Mhz cache speed.

Shortly after the review several other owners of the upgrade noted that reducing the cache speed also helped for them. However 3 owners also noted that one other thing also helped - even at the 250Mhz cache speed - and that was disabling Speculative Access using the same PL Cache Profiler utility. (Speculative Access is basically code branch prediction, which is enabled by default on all G3 and later Mac systems.)

I can only guess that disabling Speculative Access reduces cache activity (from loading/purging prefetched data) which might help mask the problem. One reader did some tests and noted that disabling Speculative Access seemed slighty better for apps performance than lowering the cache speed - although both have a minor effect usually on real world performance.

Notes on >192MB installed RAM: (from the 7/3/2001 www.xlr8yourmac.com news page)
There have been some mixed reports on problems from PowerBook G3 (Wallstreet) owners using the Powerlogix Bluechip G3 CPU upgrades. (The sample Bluechip G3/500 I reviewed back in January had problems running the cache at the default 250Mhz as noted in that review.)

" I've just had a many email exchange with the very nice head of Powerlogix Support, John Landis. The upshot of it is that Powerlogix does not guarantee that the Blue Chip will operate with more than 192Mb of RAM, which was Apple's original spec. when the Wallstreet machines came out.

I have a Wallstreet with 512Mb of RAM that is a wonderfully stable machine. I went nuts trying to make the BlueChip work reliably in my machine, following all suggestions given to me. It was only at the end of the process that Mr. Landis nicely confessed that they could not support my situation. It took so long that my dealer's 30 day money back guarantee ran out, and now I have to take a store credit.

Look into this if you like, and please indicate to the readers who trust you that this issue exists. Anyone we can save from what I just went through will be forever grateful to you.
Thanks,
Stanley K. "

I had returned the two 256MB low-profile modules to Transintl that I used for the Newer Tech PB G3/466 upgrade review and only had 192MB of ram installed for the Bluechip review, however some of the owner reports in the CPU upgrade ratings database may have been from users with more than 192MB of ram. (Check the comments in the entries there.) More RAM may increase heat (especially if using full size SODIMMs) which could be a factor perhaps. (Since the RAM size has not normally been an issue. Apple's specs were from the days before there were higher capacity modules available and as Stanley noted, it was not an issue with the original CPU.

Related Links:

• Bluechip G3/500 Review (done before OS X was released, but includes install guide page)
• The Rate Your CPU Upgrade Database has many Bluechip owner reports from Wallstreet owners (both early models and the 2nd revision wallstreet model)
• OS X on PB Wallstreet includes some Bluechip owner comments
• Newer Tech G3/466 PB CPU upgrade (tested w/512MB of ram, but before OS X was released)
• Comments on Bluechip Installs and Hard Drives from last week's news page