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Are Bad RAM Chips Common?
A semi-Anonymous Coward asks: "I recently built myself a new system using a mainboard which required using registered DDR SDRAM -- the motherboard will not work with unbuffered / unregistered memory, and I wanted the extra integrity provided by registered memory anyway. To my amazement, both the memory I purchased with the board and one of two other sticks I purchased were either defective or simply incapable of working with the board (which is the Chaintech 7KDD, BTW). About how often do people run into defective memory, and do they see them from the 'reputable' manufacturers as often as they do the 'no-name' ones? Now that I've spent a ridiculous amount of money on this, I'm a lot more wary."
I have run into bad RAM a few times, I quit buying the cheap stuff and only deal with Crucial - have had excellent luck with them.
Glonoinha the MebiByte Slayer
i have occasionally run into bad memory. a very handy utility can be found at http://www.memtest86.com to verify that your memory is bad, and the specific address ranges that are no good. you can then specify those address ranges to the linux kernel and applications will not be able to malloc the bad memory, thus running stably despite having bad ram.
I do a lot of side work dealing with computer upgrades. I outright give 2 options:
1.) We get cheap stuff and save you money. I make it very clear that it may not work
2.) We get Normally priced ram and be sure its good
Of the few people that did not want to spend the money to get a good brand even with me warning that its a bad idea about 1 in 3 ram chips did NOT work. I've NEVER had a good brand (crucial, kingston etc) fail even 1 time. I dont' gamble on my system I use Corsair XMS and thats what i recommend but anways thats what i've found.
My Rough Stats:
Cheap Memory 30%+ failed Good Memory 0% failed this is only dealing with about 100 experiances in the last few years, i don't do much side work.
Memtest86 will go a long way to test the ram. If you are going through tons of wanky ram, the issue may be your cpu or power supply however. Test the ram on a couple boxes.
As for no-name. Usually grade 'a' ram will run at a lower cas rating, where some of the generics might work at a higher (and slower) setting. Stuff that rates at PC-100 CAS 2 might only work at PC-133 CAS 3. (dang, showing my age) The good stuff tended to be able to run stable at the faster FSB and CAS settings. My time is worth more than the ~$30 bucks between solid and guesswork.
If your not pushing a system hard - cheap ram might just work. A few years back a local vendor had some dirt cheap no-name 128M sticks that ran as fast as my mushkin stuff. Go figure. You role the dice, but it matters less if you are not pushing your settings hard.
+++ UGUCAUCGUAUUUCU
Out of sight, out of mind.
Being a former test lead for a memory diagnostic tool, I'd bet you had plenty of memory errors. When they occured, they didn't 'look' like memory errors, so you treated a different problem. Your fix 'worked', so you claimed sucess and moved on. Other errors might not have symptoms -- even if corrupton did occur -- so you didn't notice anything was wrong.
The stats given by others -- ~30% failure on cheap memory and 0% on good within the first month -- are close to my experiences. IMNSHO, the intial numbers are the same (~30% & ~0%). Over the lifetime of a system +10% of both cheap and good memory tends to fail (or get wrecked by bad power).
To catch the +10% failure rate on non-ECC memory, and to catch memory subsystem errors in general, I run extensive tests on systems that can be taken down about once a year -- this is beyond any tests to diagnose flaky behavior.
Memtest86: It is excellent and as good as any other memory diagnostic software I've ever used when running all tests. As a matter of course, I add memtest86 to the boot menu on all x86 systems.
BIOS memory tests: The boot up memory tests are useful only to identify that the memory exists, so if possible I turn them off.
A firewall can not protect you from yourself. Turn off what you do not need. Do not use the firewall to do your work.
ESD damage *does* happen with a surprisingly high frequency when you handle components unsafely, but you don't notice because the damage takes time to show
I used to work at a semiconductor manufacturing facility once upon a time. Let me just say that this is 100% correct.
My employer spent a lot of money on ESD prevention because ESD errors were the worst kind of errors. Sometimes the chip would fail catastrophically, but usually it would pass probe and test and get shipped, only to fail prematurely in the field (latent failure). This is obviously much more expensive than finding the problem before the device ships.
Another common misconception is that you need to feel the ESD charge - like walking across a carpet in sock feet and touching a doorknob - in order for damage to occur. This is false - most electronic components can be damaged at a much smaller voltage than you can feel in your body.
My best advice is that simple ESD precautions like a wriststrap are cheap, so use them.
Do you even know anything about perl? -- AC Replying to Tom Christiansen post.