I have a 2009 iMac that has been working fine (but slowly) until now. I decided to upgrade the hard drive to a 500 GB Intel SSD (MZ-7TD500BW) and put in 16 GB of RAM (PNY Optima PC3-8500). I've performed a fresh installation of Mountain Lion and run memtest on the RAM. Everything passed great. I also repaired the file system permissions with Disk Utility.

But every once in a while the screen stops updating. When this happens, the mouse cursor still moves and everything seems to be functioning normally. For example, if a youtube video was playing, it continues to do so. But the screen freezes.

Has anyone seen this before, and if so, do you know a solution? So far we've been having to do a hard restart.

  • what graphics chip do you have?
    – Ruskes
    Apr 21, 2013 at 13:36
  • This is most likely your SSD being slightly incompatible with OS X. The freezes are when the SSD do not do exactly as OS X expects so a timeout need to occure "somewhere". Is the drive specified to be compatible with OS X? Apr 21, 2013 at 13:46
  • I'm not sure if it is or not, but I figured a popular brand like Intel would not be a problem. I also figured that they are both supposed to follow the SATA spec. Do you know of a list anywhere that shows which SSDs are compatible with OSX?
    – cayblood
    Apr 22, 2013 at 16:25
  • Buscar, the graphics card is an ATI Radeon HD 4850 with 512 MB, ROM revision 113-B9110C-425, 01.00.383.
    – cayblood
    Apr 22, 2013 at 16:44
  • Thorbjørn, the thing that's weird about your hypothesis is that the computer is not really locked. It's still working. The only thing that has happened is that the display is no longer being updated.
    – cayblood
    Apr 22, 2013 at 16:45


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