Power On Self-Test Failure, External Cache Failed

If you still have a month left on your AppleCare, get going and get the PowerBook repaired ASAP!! It sounds like your logic board is failing which will be extremely expensive to fix (around $800 through an Apple Authorised Service Centre).

jp

PowerBook G4 12" Aluminium Mac OS X (10.3)

I just noticed the same thing with my 1GHz G4 17-inch Powerbook. I haven't necessarily noticed any decrease in performance, but I recently noticed that System Profiler: Hardware: Diagnostics says Power On Self-Test Failed, Failure type: External Cache. So we ran the full range of Apple Service Diagnostics, and everything passed, but the hardware profile says L3 Cache is zero. I would have thought a bad cache would render my machine inoperable, but it's running without apparent problems. I bought the machine used about 6 months ago, and it's very possible it had this condition when I bought it. Am I getting degraded performance as a result? Is my machine (and data) in danger of failing? The spec sheet says my machine is supposed to have 1MB of L3, but my machine seems to have none. What's the deal? "About This Mac" doesn't make any mention of an L3, but I don't know that it ever did.

G4 17-inch PowerBook Mac OS X (10.4.4) 1GHz/1GB

Hi, justinulysses. Yes, you are getting degraded performance, since the OS isn't able to make use of the failed cache. But if you aren't actually suffering any annoying delays or other malfunctions, you can choose to ignore the problem unless or until you do. I would, in your shoes. A new logic board is the only remedy, and that's quite expensive.