RAM for MacPro

[Jeremy Garchow]

What kind of issues?

[Sean Oneil]

Use TechTool Deluxe and run a memory test.

Sean

[Mitch Sink]

[Sean ONeil] “Use TechTool Deluxe and run a memory test.”

Hi,

Running memtest in single user mode tests more memory and its free or a few dollars:
https://www.memtestosx.org/index.php

Here are some excerpts from an article (if you install memtest in the the root level of your boot drive it will be a little easier to run):

The above discussion begs the question, “How can I tell if my RAM is bad?” If the problem you’re having is repeatable — meaning you can predict when it will occur (at startup, when burning a CD or DVD, when you open a large file in iMovie or Photoshop, etc.) — then the simplest way to test your RAM is to shut down your Mac, remove one of your RAM chips, then start your Mac up again and see if you can reproduce the problem. If you can’t, there’s a good chance the RAM chip you pulled out was the culprit. If you can reproduce the issue, chances are the pulled memory wasn’t the cause. Assuming you’ve got more than one RAM chip installed, repeat the process, reinstalling the “tested” chip and then removing a different chip each time, until you’ve either found the bad module or eliminated “bad RAM” as the cause (in which case it’s time to move on to other possible causes).

Unfortunately, if the only memory in your Mac is what came with it, and you don’t have any spare RAM chips to swap with that memory, then you can’t use the above testing method. It’s also difficult to use this method if your problems are intermittent and unpredictable — if you’re experiencing kernel panics or system freezes that don’t seem to correlate with any particular action or event, you can’t determine if removing RAM or swapping it out fixes the problem. Or perhaps you’ve got a lot of installed RAM and you don’t want to go to all the trouble of testing each chip separately. What you need is a way to test your RAM just as you would test your hard drive using Disk Utility or a third-party utility such as Alsoft’s DiskWarrior.

I’m not going to get into the nitty-gritty of how Memtest works; to put it simply, Memtest writes data to chunks of RAM, and then reads that data back from RAM to verify that it’s the same. If it isn’t, there’s a problem. If it is, even after many, many testing cycles, it’s a good bet that those chunks of RAM are good. By testing every chunk of a RAM chip in this manner, Memtest gets a pretty good idea if the chip is good or bad. (There are several ways a memory-testing utility can verify data saved to RAM; Memtest uses multiple methods in order to test thoroughly.)

Memtest has proven to be so good at what it does that I consider it a must-have troubleshooting utility — one of the first things I do when I’m having serious problems with a computer is use Memtest to test the computer’s installed RAM. I also recommend using Memtest whenever you add RAM to your Mac; after all, you may as well make sure your new RAM works properly before trusting it with your data, right?

Using Memtest

If you don’t have much Unix experience, once you’ve downloaded and expanded the Memtest folder, you may be a bit intimidated — it contains a number of Unix executable files. But don’t fret; it’s actually quite easy to use.

To install Memtest, simply drag the Memtest folder to your /Applications folder. (Unix gurus may prefer to install Memtest elsewhere; either approach is fine.) You can then run Memtest either when booted into Mac OS X or when booted into single-user mode. The former is easier; the latter allows Memtest to test more of your RAM. (Memtest can’t test RAM currently being used by the OS or by applications.)

When booted into single-user mode. The other way to run Memtest is in single-user mode. Doing so is similar to the instructions provided above, except that you have to type the path to the Memtest application manually:

1. Make sure you know that path to the Memtest application.
2. Restart your Mac, holding down Command+S; this boots your computer into single-user mode.
3. Type the path to the Memtest application followed by all 1 — this will most likely be:

/Applications/memtest-4.05M/memtest all 1

4. Press the Return key to start the test.

Memtest will run just as it does in Terminal; however, a significant advantage of running Memtest in single-user mode is that because Mac OS X hasn’t yet staked a claim to large amounts of your RAM, Memtest is able to test more of that RAM than when run in Terminal when booted in OS X. When Memtest has finished, assuming your RAM passes all the tests, type exit and then press the Return key to continue booting into Mac OS X.

(Note that if you’ve got a Power Mac G5, your Mac’s fans are likely to turn on — full blast — while Memtest is doing its thing. This is normal, as the software that normally controls fan speeds on the Power Mac G5 based on temperature monitors inside the case isn’t loaded in single-user mode; your Mac is simply playing it safe by turning all the fans on. Once you boot into OS X again, your fans will settle down.)

Since I can’t cover every detail or scenario in this column, I highly recommend that you take a look at Memtest’s documentation and FAQ before using it. But apart from the scary-to-some Terminal commands, it’s actually quite easy to use.

Best Wishes :),

Mitch