Archive for February, 2011

Solving Snow Leopard Crashes on a 24″ iMac

February 3, 2011

My 24″ iMac (early 2008, Core2 Duo 2.8GHz) came with MacOS 10.5 Leopard and worked great with it. When 10.6 Snow Leopard came out, I upgraded to it, and thereafter the iMac started crashing 1-3 times a week. The screen would turn black, or gray, or striped. It wasn’t totally dead, which would suggest a power supply failure. It wasn’t a kernel panic (with the multi-lingual “You need to restart your computer” message), which would suggest bad RAM. But it was hung and couldn’t be reached over the network. To recover, I had to hold down the power switch to force a shutdown, then turn it back on.

It happened sometimes while the machine was idling, other times while I was in the middle of doing something. This persisted through the 10.6.4 update, at which point I decided MacOS updates weren’t going to fix it.

I tried a clean install of Snow Leopard, but that didn’t fix it. I replaced the RAM with a different brand, but that didn’t fix it. I had the main logic board replaced under AppleCare, but that didn’t fix it. After some searching of the web, I found the solution. It confirmed my hunch that the video chip was overheating. The video chip (GPU) in mine is an ATI Radeon HD 2600 Pro. Apparently Snow Leopard drives the GPU harder than Leopard does, but runs the iMac’s fans at the same barely-audible speeds. The problem is more likely to occur on iMacs that are left on all the time, as mine is.

The solution is to install a third-party fan control program to force the fans to run faster and keep the inside of the Mac cooler. I installed iMac Fan Control. The iMac’s fans are now audible, but not too objectionable, and it hasn’t crashed in the two months or so since I installed iMac Fan Control. The temperatures are significantly lower than before. Here is a picture of my iMac Fan Control System Preferences panel.

Update: A year after installing iMac Fan Control, the iMac hasn’t crashed even once from the video chip problem. It’s currently running MacOS 10.6.7 plus the Snow Leopard Font Update.


Buying SATA Hard Drives

February 1, 2011

I have a few recommendations on purchasing hard drives for desktop or laptop computers. I don’t have much recent experience with enterprise-class drives (SCSI, SAS, Fibre Channel, etc.), so I won’t speak to those.

It’s weird how things change. In the ATA/EIDE days, I swore by Seagate and Samsung hard drives. IBM/Hitachi made “Deathstars” (several models of Deskstar drives had very high failure rates; all four of mine died prematurely). WD (Western Digital) had firmware compatibility problems with a lot of chipsets (including G3 iMacs, which couldn’t go to sleep with a WD drive installed).

In the SATA era, it’s reversed. Hitachi and WD Black SATA drives have been reliable and widely compatible in my experience, while Seagate and Samsung have problems with both high hardware failure rates and firmware bugs. The reliability of Seagate hard drives plummeted when they switched to perpendicular recording with the Barracuda 7200.10 line, and it still hasn’t recovered. Most of the dozen or more Seagate desktop and laptop drives I’ve gotten since 2007 have failed. Samsungs from a couple of years ago (the F1 series) reportedly had a lot of problems, so I avoided them, but the F3 series seems to be better, based on searches of reviews (I don’t have any personally). I also avoid WD Green drives after having problems with them unmounting randomly.

I no longer buy hard drives from NewEgg or Amazon because of substandard packaging, leading to higher failure rates from shipping damage. PC Connection, B&H, and OWC all package hard drives better.

When buying external drives (USB/Firewire/eSATA), I prefer buying the enclosures and drives separately. There are several reasons:

  1. It gives me the flexibility to choose both the enclosures I want and the drive models I want.
  2. Warrantees on bare drives are generally three years, but warranties on drives in external enclosures are only one year, for some reason.
  3. I want to ensure I’m free to swap out a drive from an enclosure without having to break the enclosure or void a warranty. For example, to plug it directly into a motherboard to check the S.M.A.R.T. status. Although that’s unnecessary for drives and computers that have eSATA connectors, at least half of my drives and computers don’t.

My preferred external enclosures are the Mercury lines made by OWC. They have proven generally reliable and sturdy over the past eight years, keep drives cool enough without fans, and use high quality chipsets. There are a few other good manufacturers of external enclosures; I have seen recommendations for LaCie, NewerTech, Glyph, and Granite Digital. But after some experimenting, I have stuck mostly to one manufacturer to avoid having to deal with a proliferation of different power supply connectors. Recently I have started also getting G-Technology G-Drive external drives, which are made by a division of Hitachi. They use the same power supply connectors as my OWC drives and seem to be good quality.

I avoid having important data on only one hard drive. I normally buy hard drives in pairs made by different manufacturers, so if one model of hard drive should turn out to have a short lifetime, the other copy of that data will be on a different brand of drive and be unaffected. This approach has saved me from losing a lot of data over the years. I’ll describe in another post how I keep the pairs of drive synchronized.