The importance of removing "bad" RAM from your Mac

[bobw]

From MacFixIt

One of the most common culprits of general system instability, problems installing or re-installing Mac OS X, and various other issues is defective RAM. Mac OS X 10.2.x in particular has been noted as being "picky" about installed memory.

You can easily determine if you have a "bad" RAM module by using the Apple Hardware Diagnostic CD, included with all currently shipping Macintosh models. To use the Apple Hardware Test CD, restart your computer while holding down the C key until the "Loading..." icon appears.

Note that the Apple Hardware Test can not be used when a mouse is directly connected to the USB port on the display or on the iBook. Apple says "Please connect the mouse to a USB keyboard."

Our friend Erin Duckhorn at Crucial Memory writes "With the cost of RAM being so low (across the board), people often think that all RAM is the same and they can get by purchasing the cheapest RAM out there. Not true! Stability and performance are directly tied to the quality of RAM used. This is particularly important for Mac users who tend to use very memory-intensive software."

Duckhorn also pointed us to a document on the Crucial Web site that describes "top tier" and "generic" memory:

Top Tier Memory After going through this extensive series of tests, you can be confident that the passing parts will work for a long time.

Generic Memory So what happens to the parts that failed testing? Some get thrown out, but many are re-tested and graded to lesser speeds and/or conditions (i.e. without guard bands). Others aren't even re-tested (even though they might not have gone through burn-in). Yes, these lower-grade modules will probably work today, but they're more prone to marginal performance and failures, especially over time. DRAM manufacturers often sell this memory to third party vendors who then re-label them with their own brand name.

Unfortunately, it appears that Apple semi-frequently ships Macs with at least somewhat defective RAM modules. Apple does not disclose its component suppliers.

While browsing through the eJournal of Dan Gillmor, an editor with the San JOse Mercury News, we found this case example of a "bad" RAM headache:

"I have a dual-processor G4, 800 MHz, purchased new. For nearly a year I had intermittent crashes, freezes, memory problems, app shutdowns, you name it. I reinstalled the entire system numerous times. 75% of the time I couldn't even get the OS reinstalled, I'd have to try 3-4 times to reinstall it. I could never get a good incremental upgrade past 10.2.3. It was very frustrating.

"One day about a month ago, I was pawing through the stack of disks that Apple provided with the computer, which I had never opened. It was the HW diagnostic disk. I decided 'What the hey' and ran it. Immediately it identified that I had a bad RAM DIMM. I remembered that I had mail-ordered a new DIMM about the time that the crashes started.

"I removed the DIMM, going back down to 512MB, and all was immediately well. I then went out and purchased another new 512MB DIMM locally at a store (in case it was bad and I needed to return it). Installed it and all has been well since. I have not had a single crash, kernel panic, or any other (strange) behavior since [...]"

[Dime5150]

I have a 512 stick of the more quality tested ram. But I have another 256 stick of the "cheaper". I've never ever had a kernal panic or any other strange behavior ever.

I guess it just depends but I wouldn't be so quick to go after the ram excluslively.

[Arden]

Thanks for the information. That should surely help some potential "Help! Everything's defective!" posters.

IMO, this should be in the How-to section, but that could just be me. Your call, Mr. Mod.

[voice-]

I had a case with my old PowerMac which I found queer. I had 128MB of RAM, added 128MB more. Then I added 256MB more into the 3rd RAM slot. After a while I bought another 256MB chip and added it into the 2nd RAM slot, removing the 128MB chip. My OS insisted that I had 384MB RAM, it refused to see the 256MB chip in slot 2. After a while, in desperation, I switched the positions of the 2 256MB chips and suddenly all my RAM is recognized...

[applewhore]

I had the same problem with my last 15" PB - I bought two 512MB memory cards - but from different places...

My PB told me I had 768 MB... (as they say in the U.S., "go figure"!)

Change of "non Apple" second card and I was flying again with 1GB. yummy...

"always buy the best you can afford"

[Arden]

Picky, picky.