The Core Shutdown Feature/Flaw
The Santa Rosa platform comes with dynamic acceleration technology. It allows single threaded applications to execute faster. When a single threaded application is running the CPU can turn off one of the CPU cores and overclock the active core. In this way the CPU maintains the same Thermal Profile as it would when both cores are active.
So, by design, the Santa Rosa platform will throttle itself to keep the heat down.
I kicked myself for missing this while researching the problem. I should have looked at the CPU specs once I knew the core shutdown was responsible for the performance degradation, but I didn’t. Mea culpa. I was thinking as a consumer, not as an IT professional.
Please note: I do not think this excuses the problem. The UI freezes, stuttering, and slowdowns remain unacceptable. The CPU ruins the user experience, which is a bug. A feature that acts like a bug is a bug.
But it does explain it, and therefore allows us — consumers and Apple alike — to address it.
If the Santa Rosa platform is the problem, which I now believe it is, there are very few options available for MacBook Air owners. Either you live with the performance hits, and hope that it is fixed at a later date, or you don’t.
It boggles the mind when you consider the anecdotal return rate that units who don’t exhibit this problem may actually be defective! There are plenty of MBA users who are gambling that they’ll get one of those in the replacement cycle. But not me.
If anything, finding out that this problem is a design feature/flaw strengthened my decision to get off the Air platform (and increased my nostalgia for the PowerPC chipset, but that’s another story.) I am frustrated that it took so long to identify the root cause, but relieved to know that gambling on another unit isn’t worth it.
Since my case dragged on for several weeks at AppleCare, and therefore attracted a bit of attention from management, I used the opportunity to make a few suggestions to them.
- Educate Support: Product specialists need to know about this behavior and be able to explain why it happens, and what benefits it brings (if any). First-tier troubleshooting should be revised to better diagnose real mobo problems.
- Educate Consumers: Apple needs to address this issue publicly with a technote to stem the tide of replacements.
- Fix it in the OS: You can’t change the chipset, but serious efforts can and should be made to reduce the effects of the core shutdown within the OS and better manage single core mode invocation.
The first two suggestions can reduce agent support costs and reverse logistics expenses, as well as improve customer loyalty. I’ve run customer service organizations before, and I know the band-aids you can apply to make support more effective.
The solution lies in #3, though: fix the damn problem.
Sadly, that’s beyond AppleCare’s ken.
Special thanks to Artifex and Mike Rose for publicizing this problem, Josh Kagan for his insight into the Santa Rosa platform, and everyone on Twitter who’s listened to me gripe about this for the past three weeks.
This is: brett's logjam → The Core Shutdown Feature/Flaw.