Quad-core MacBook Air?

[ericmurphy]

I have a mid-2011 13" MacBook Air that I always thought was a dual-core machine (it's a 1.7 GHZ Core i5). In fact, Apple's "Tech Specs" page lists it as a dual-core CPU with 3 MB shared L3 cache.

But Activity Monitor seems to think it's a quad-core part. The "CPU" tab shows four cores, as does the CPU usage window. What gives?

My dual-quad Mac Pro shows as a 16-core machine in Activity Monitor, but that machine has Xeon processors with Hyperthreading enabled. But I don't think Core i5s have Hyperthreading, or if they do, I don't think it's turned on in MacBook Pros.

Anyone have any ideas as to what's going on here?

[ElDiabloConCaca]

The Core i5 does, indeed, support Hyperthreading, which probably explains the number of cores you're seeing in Activity Monitor.

[ericmurphy]

Interesting. My iMac at work has a Core i5 quad-core, but it only shows the four processors in Activity monitor. Maybe Hyperthreading is turned off in the iMacs?

[ElDiabloConCaca]

Strange and interesting -- both computers use mobile variants of the i5 -- perhaps you're correct.

Are both the iMac and the Air running the same version of OS X?

[ericmurphy]

Yep, they're both running 10.7.4. The MBA is a year newer than the iMac, though; they might have slightly different varieties of the Core i5 (plus they're obviously running at different clock rates).