5 Replies Latest reply: Mar 16, 2010 1:19 AM by Roald Hoolwerf
bobritter Level 1 (5 points)
I took delivery of two 27" imacs within a couple of days of each other, one for home and one for the office. One (the office unit) is an i5, the other is an i7. (I had only planned to buy the i7 for home, but we had some uninvited guests go through the office the night before the i7 arrived who took my 4 year old MacPro when they left, so the i5 is a replacement for that machine).

For reasons that I can't figure out, Activity Monitor is acting differently on the 2 machines.

On the i5, when I look at CPU Usage, there is a black window near the bottom of the Activity Monitor window with 4 rows of moving activity monitors in it, one for each CPU core. The dock icon, which is set to display usage, also has 4 columns, one for each CPU core.

On the i7, on the other hand, the black window at the bottom of the main program window shows only one window with what appears to be a single moving graph for the machine as a whole, and the dock icon also shows only one column. There is, however, a separate small grey floating window with 8 "live graphs" in it, independent from the main window. 4 of the graphs appear to reflect the 4 CPU cores, while it is not at all clear what the other 4 graphs represent - they alternate with the 4 that appear to be for the CPU cores, and only show occasional activity.

There was no difference in how the machines were set up - what's the difference here? And what are the other 4 graphs on the i7's little grey window representing?


iMac i7 / iMac i5 / MB Pro 2.8 (17") / MB Pro 2.4 (15") / MB Pro 2.4 (17"), Mac OS X (10.6.2)
  • Carolyn Samit Level 10 (102,820 points)

    No idea why these are different. Try deleting the preference file associated with the Activity Monitor on both Macs.

    I just checked something. On my iMac running 10.6.2 the Activity Monitor version is 10.6 (210)
    On my PowerBookG4 running Tiger 10.4.11 AM version number is 1.5 and look the way you described.

    Bob, the 15 and 17" are both running Snow Leopard?

  • Tom A. N. Level 1 (0 points)
    There must be something wrong with the Activity Monitor, as I got the same problem on my new i7 iMac. The 8 graphs you refer to is the 8 cores the system sees. Intel have been utilizing a technology for some years now called Hyper-Threading, which makes the OS see 2 virtual processors for each core present. See here for details: http://en.wikipedia.org/wiki/Hyper-threading
  • CaptainBG1 Level 1 (25 points)
    Activity Monitor hasn't been updated to work with 8 cores. Since the i7 has 4 physical cores but 8 virtual cores, mac os sees 8 cores and Activity Monitor just doesn't display those graphs correctly. However, 3rd party solutions like iStat do.
  • bobritter Level 1 (5 points)
    Sorry for being gone a while - I had a detached retina and am just now able to see the screen well enough to respond...

    So the hyper-threading of the i7 makes 8 cores, as far as the OS is concerned? Does the i5 not also utilize hyper-threading? Maybe not, I guess, based on a quick online check.

    I'm unaware of any other significant difference between the 2 machines. Both are running 10.6.2, and both report the same build number (212) for Activity Monitor.

    Seems unlikely to say that Activity Monitor hasn't been updated to deal with the i7, however. More likely it is simply that this is the new way of dealing with reporting the activity of the 8 cores as seen by the OS. It isn't a bad solution - having an 8 bar graph in the dock would either take up a lot of room, or be so small as to be useless. The separate window, which I keep down in the bottom left corner of the screen, works just fine. I just couldn't figure out why the 2 machines worked differently in this respect.

  • Roald Hoolwerf Level 1 (40 points)
    The i5 doesn't use HyperThreading, the i7 does. HT means that the machine sees 8 virtual cores indeed. ActivityMonitor doesn't show this properly in the Dock, something like iStat Menu's shows it just fine.

    I have to say, recoding a video and seeing all eight cores going full power is quite an impressive sight!