Slashdot Mirror
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.
For a lot of the FreeBSD / Samba server that I use, I simply remove most of the memory. Less memory - less risk that the the system will run in to a bad batch. Don't remove so much that you end up trashing (trashing could expose errors in the bus or potentially over-strss your hard-drive) - but for normal (not high performance) file serving, nothing is gained by having huge quantities of memory.
Moneyed corporations, non-working 'poor' and criminal prisoners are turning productive citizens into tax-slaves.
I've used all sorts of different RAM in many systems:
My SGI Indy is using old 72-pin SIMMs that I found on my (carpeted, read: static-inducing) floor under my desk.
My SparcStation 20 uses RAM that was shipped to me rattling about in a cardboard box without any packaging material whatsoever.
My K6-2/400 used crappy no-name (not even a brand to be found on the chips themselves) 256mb PC100 DIMMS
My Athlon TBird-1.4 used the cheapest no-name crap DDR RAM I could find on Pricewatch - 512mb of it - but at least Infineon's name was printed on the chips.
My Athlon XP1800+ used just about the cheapest RAM possible (I bought it from NewEgg instead of some other vendor for about $2 more) with no names on the modules or chips.
A Dual Athlon MP2000+ server I built uses no-name Reg. DDR266 / 512mb from a Pricewatch low-baller.
My current P4/2.4 uses 256mb DDR266 by OCZ Systems, and not because of the brand recognition (who the hell are they?) - it was super-cheap. I bet if I removed the RAMsink on it, the chips would be nameless.
None of these systems have ever had memory problems. They rarely, if ever, crash (or at least they didn't crash when I had them - some have passed on into the hands of friends). Maybe I'm just one really lucky bastard when it comes to RAM, but I've never had any problems buying the cheapest shit memory so that I could save a few bucks.
Also, somehow, I have managed never to kill a component with static electricity. The worst that's happened is that I rebooted my Atari 800 by zapping it right on the motherboard while it was running. In fact, the only component that I've ever bought or installed that didn't work was a Sun Creator3d framebuffer - the only component I've ever used an anti-static wristband to install (because there was a free one in the box) and it was DOA with big vertical lines running through the picture at regular intervals (4 pixels). Well, that and two Fibre Channel drives that exploded, but that's because I was hot-swapping them and shoved the power connector into the (worn-down, self-installed) receptacle backwards.
Every cloud has a silver lining (except for the mushroom shaped ones, which have a lining of Iridium & Strontium 90)
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
Why does the computer industry tolerate this sort of thing? When it was hobbyists tinkering with Northstars and Cromemcos and Sols it might have been understandable, but we should have grown up a long time ago.
When you put oil into your car, you know that the oil companies and the car companies have gotten together with the American Petroleum Institute to set standards so that as long as your owner's manual says "API SG" and the oil you buy says "API SG" or better, that oil will work in your car. And you can use Mobil Oil to top up an engine filled with Quaker State without losing any sleep over whether their chemistry is compatible.
You don't rely on friends' stories of whether Quaker State is better than Shell Oil. You know that regardless of the price of the oil, if it says API SG it meets API SG specs and if your car says API SG specs are good enough, they're good enough.
It doesn't benefit anyone if your engine seizes up, and it doesn't benefit anyone if your computer crashes.
It's simple, it's easy, millions of consumers who aren't chemical engineers buy engine oil every day without wrecking their cars.
Why is it expecting too much for computer vendors to do the same?
And, while we're at it, why don't all computers use parity-checked memory? This was standard on 100% of all computers before the micro age, and for some reason people started putting in non-parity memory to save money and asserting that "it works."
And our computers crash a lot, and nobody knows why and nobody does anything about it and everyone just accepts that that's the way computers are...
"How to Do Nothing," kids activities, back in print!
Ok - to summarize
1) whenever you buy a new stick of RAM, run memtest 86 on it for an hour or so. It can save you weeks of problems.
2) Use a grounding strap. ESD damage is a serious problem, and especially in the winter months, can easily lead to zapped parts. In fact, use a strap whenever you open your box! I even have a roll-up ESD mat for serious surgery.
I have actually had memory go bad in my PC right when I was using the PC: it was good one minute, then bad the next. I have a nice APC UPS working as a surge protector. THe memory was some premium stuff too - Corsiar XMS memory. I hadn't touched the inside of the box for a few weeks (hard to believe, huh?), and I was practicing with the 203 on America's Army, and I suddenly got a win2k BSOD (which has a lot more words, but is basically just as useless as the win98 BSOD). So:
3) test your memory periodically - like every 6 months or so.
4) Maybe your motherboard has some debris in the memory slot or a sliver of metal shorting some pins out.
No, I don't trust in god. He'll have to pay up front, like everybody else.
I don't buy ram very frequently but I have never run into bad ram, and I always buy the cheapest I can find.
My one encounter with "bad" ram was in a computer hardware class I took a few years ago. Two other classmates and myself were usually given special tasks by the professor because the class was so stupidly easy for us. One day, after we finished our two hour lab in fifteen minutes he gave us a stack of 8meg simms (this was a while ago) to test with some software he had. We tested about six and every time one or all of them came up as bad. Being 18 year old computer geeks we decided could keep the bad ram for keychains. The next week he told us to try the test with known good ram, and it turned out that the program was faulty not the ram. My fully functional $30 keychain has since fallen apart but I sometimes wonder if he every counted the ram in the closet at the end of the semester.
At no point did you say that you've verified that your motherboard is good. If you keep swapping out RAM and all of it seems to be bad, I've got news for you: it's not the RAM that's bad.
Under capitalism man exploits man. Under communism it's the other way around.
I'm responsible for 250+ PC's and a dozen servers. Over the last couple of years I have bought literaly hundreds of sticks from Crucial. Never a single bad chip, never a compatability issue, never any problem whatsoever. Period.
I have two Abit KG7-raid motherboards, using Crucial registered pc2100 ddr memory, no problems at all.
:)
You're right about the flexing though - only if you've not installed the motherboard correctly. I did this once. There's a screw mount near the ram slots that I overlooked, and if it's not there the motherboard will flex right down to the case's motherboard mounting plane. This being my first experience with an ATX power supply (ie: ones that aren't actually off when the computer is shut down, and have a manual power switch at the back), I didn't manually turn off the power or even unplug the cord (duh!) So when I pressed the ram in, my mobo flexed and shorted out on the case - huge sparks and all sorts of wonderful language and a dead motherboard (ram was perfectly fine though!) Lucky for me I managed to get the mobo replaced on warantee
Anyway, moral of the story is - install the motherboard properly and you won't have this "flexing" problem. Look for the screw mounting hole near the ram slots and make sure you put a mounting peg in there.
-kidlinux.
Comment removed based on user account deletion
You can take precautions without a ESD strip. Unless I'm working on raw chips, or very, very expensive pieces of equipment, it's not worth the hassle. Nobody is going to bother, so here are some much easier to follow words of wisdom:
ESD advice for system self installers:
- Ground yourself to the metal chassis or something comparable on your system before you start assembling things. Do this frequently.
- Leave things in the anti-static bags until you're ready to put them together.
- Don't handle ram chips by the pins. Handle the modules by the edges of the package. If you can't get them into the system like this, then move the system so you can. This advice is good for motherboards, hard drives, system cards - handle them by their edges only, not on the pins or where the socket connector is.
- Never handle a cpu by the pins. Ever.
Taking those basic precautions will get you a long life and few problems without the hassle of wondering where a ESD strap is. Memtest is your friend, and use a good power supply. If you need to ask, odds are you don't have one.
..don't panic
Essentially the high voltage of the ESD (ESD like when you shock yourself on a doorknob is very high voltage, it's just very low current) is destructive to the transistor junctions, but it usually doesn't cause immediate complete failure. A few days, months, or even years down the road, the junction will prematurely break down, having had a shortened lifespan because of the ESD damage.
Indeed.
Memory chips - and most other components within any computer less than fifteen years old - use CMOS logic. CMOS stands for "Complementary Metal Oxide Semiconductor", which essentially means that they're full of MOSFETs ("Metal Oxide Semiconductor Field Effect Transistor"). This includes almost all processors, support logic, etc. In fact, the only exception which comes to mind is the really old computers which had the big banks of 74xx-series TTL logic all over the place, like in an XT. But keep in mind that the processor itself - and many other components - will be CMOS.
The neat thing about Field Effect Transistors is that the electric field created by applying a gate voltage turns on the source-drain circuit. There is essentially no current required to drive the gate. The fact that there is theoretically no gate current means that you can do things like power 20 million transistors off a single 200W AT power supply, or build a wristwatch which runs for 5 years off the same tiny little battery.
The "field effect" is governed by the inverse square law. As you double the distance, you need 4 times the voltage to achieve the same field inside the source-drain junction. Naturally, in order to be able to work at the low voltages inside a computer, the distance therefore must be tiny.
This tiny distance is filled with a layer of what is, essentially, glass. And it's so thin that it can have a hole blasted through it by 30 volts.
Now, air doesn't ionize until about 3kV per millimeter. That means, to jump a 1mm gap, you need about 3,000 volts, which you perceive as a tiny static electric spark.
You will never see, nor feel, a 30V static electric charge. You can build it up just by sitting in your chair. And that's enough to blow a MOSFET transistor.
If a RAM chip has a million MOSFETs (modern ones have a lot more!) and you blow one of them, your chip is still well over 99.999% fine... until you try to read back data from the address with the blown MOSFET. And then you get one bit of garbage.
The data in RAM is corrupt. What if it's executable? Does the machine crash? Probably. What if it's a JPG? Maybe one pixel on that 1024x768 pr0n image you downloaded is one shade of skin-tone different than it should be.
A lot of ESD failures show up as intermittent crashes and other software problems. Before you reinstall your operating system because it's getting crufty, consider your hardware... well, unless you're running Windows.
ALWAYS wear a wrist strap. It's a bummer, but them's the dice.
Fire and Meat. Yummy.