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Salvaging Defective DRAM
An anonymous reader writes "Ever wonder what happens to DRAM that fails quality assurance testing during manufacturing? Turns out a lot of it ends up as 'downgrade' memory and ends up in OEM memory modules. Last resort: use it in an answering machine, where the sampled audio can be very tolerant of bit errors."
Comment removed based on user account deletion
"Oh you left a message on the answering machine, naah I didn't get it must be the defective DRAM chips they use. Now you've managed to track me down using a detective agency I'll be sure to send you the cheque next week"
An Eye for an Eye will make the whole world blind - Gandhi
You just explained a lot about my fricking answering machine! I thought that no one ever called! And now I find out it is low grade ram? My god! I may really HAVE a social life!
ad logicam Claiming a proposition is false because it was presented as the conclusion of a fallacious argument.
No. I figured they forgot about it.
...I forgot it. Musta been that defective OEM memory module I had implanted in my skull...
-RickTheWizKid
BadRAM patch.
Summary: This page proposes an approach to support RAMs with defective addresses, This may open interesting business perspectives, where those RAMs can be sold under a white label for less money rather than discarded of without any profit.
the url is:
http://rick.vanrein.org/linux/badram/
and I suddenly though, hmmm what happens to that defective DRAM, I open up Mozilla and what do I find an answer to my question.
This is the prime example of why I tell people I know not to buy ram off of the internet unless its from a major company that has good support. To many people buy 15-90 day warranty ram because its cheap, and when it fails they are upset that they have to replace it. If you pay a bit more money you get lifetime warranty ram... and why do you think they are willing to warranty it that long, because they know it works. people dont understand the testing process and think they are getting the same product buying cheap ram, as opposed to inexpensive ram...
Fire in the hands of the village idiot is no tool, but a weapon of mass destruction
Sheesh, evil *and* a jerk. -- Jade
I recall seeing an article awhile ago where companies were buying defective memory, and running them in these external testing units,which would identify which chip(s) on the stick were bad. I'm assuming they'd then unsolder the bad chip and recover one from another module. At that time some of those sticks had 8 chips on each side, so you could recover 15 good sticks from 16 bad ones. Considering the price of memory a few yrs ago, it was probably a worthwhile venture. Nowadays though, it's probably not worth anyone's time.
I work for the Department of Redundancy Department.
I sh*t you not.. they make great keyring fobs! just dont let your gf see it ;)
moo
There are some things in the article that are pretty out of date:
To reduce the test time, parallel chip testing usually is accomplished with eight to 16 chips in a row.
That's pretty low parallelism; there are memory testers out there that test over 200 devices at a time right now. And even the older, more common systems are probably testing 64 in parallel.
A special ink jet color marks the good dies.
This hasn't been true for years. Each device's pass/fail status is stored in a database, along with all other test results, and the whole process is automated enough that good die are binned out automatically. No need to physically mark the chip.
Due to the imperfection of the process, a percentage of the DRAM die contains some faulty cells.
That percentage is 100%. At modern memory sizes, you never get a perfect device without going through repair.
Well, have you ever wondered what happens to all the defected people that get produced?
They end up on earth.
I've been waiting for the computer graveyard market to ramp up. Where does the rest of defective computer systems go?
It's in my closet. All of it. The whole market. I'm waiting for the entire tech market to crash, so I can flood the market.
-- Having a Creationist Museum is like having an Atheist place of worship
Needless to say I find this very cool indeed, but I'm not sure I'd want to run it on my high availability, mission-critical web server for a bank ;-)
-WolfWithoutAClause
"Gravity is only a theory, not a fact!"There are a lot of peeps complaining about substandard ram. If you had RTFA, you'd realize that the downgrade ram is reconfigured to skip the bad parts in the chips, so that it comes out as a normal module. Just because there is a faulty bit or 10 in a modules, doesn't mean the reast of that module is bound to fail. It could just have been an imperfection in the silicon or the circuit process.
:(
The downgrade ram has to pass further tests to insure the detours around the bad parts worked.
Granted, I probably wouldn't use this stuff in a mission critical server, but if you are buying for a mission critical server, you should be getting ECC registered with lifetime warranties anyway. Now for a small web or file server, or even a desktop, I'd use this.
Other people have mentioned memtest86. This program is your friend. Don't even bother with BIOS POST tests of RAM, just use this every once in a while if you REALLY want to find the problems. Too bad it won't run on my alpha server
-- Having a Creationist Museum is like having an Atheist place of worship
DRAM chips are usually have either 4, 8 or 16 bits per word. In order to construct a DIMM, 64 bits are needed. This means that with 4 bit DRAMs, you need 16 chips, with 8 bit DRAMs you need 8 vhips, and with 16 bit DRAMs you need 4 chips. usually you will see only the 4 or 8 bit DRAMs, because these occupy less board area for the same capacity. 16 bit DRAMs are only used for low capacity DIMMs.
When your DIMM supports ECC, it's 72 bits wide, which makes it more complicated. Usually its made of 18, 4-bit chips, or 9 8-bit chips.
(back in the 30 and 72 pin SIMM days, when memories were 8 or 32 bit wide, you could see ECC SIMMs that use 3 chip for 2x4+1=9 bits, or 2x16+4=36 bits).
If you see DIMMs with 12 chips, This is usually a cheap OEM SIMM using partially good DRAMs.
The Best way to identify such a DIMM, is to write down the marking on ALL the chips on it, and look them up in the internet. You then sum up all the DRAM bit widths, and see what you come up with:
If its 64 bits, its a normal DRAM.
If its 72 bits, its probably an ECC DIMM.
If its more, it's probably a DRAM using partially good DRAMs.
I wonder, does RAM faults develop over time, or are they introduced in manufacturing? That is, if you have some bad RAM, and correct it with Linux BadRAM, can you then be reasonably safe you won't get more faults?
Dead pixels on LCD screens are like this, if you don't have any dead pixels, you'll never get any. But how about RAM?
The Sinclair Spectrum used half working 32k memory chips for cost reasons. In the later models, the computer used the same system, even though by then they were using mostly working chips as the cost of memory had fallen.
You can get an extra 16k on most speccys by soldering a couple of links.
Reel advice for Linux users with bad ram.
Run memt86 and use the output for the badram patch for the kernel.
that will actually work and cut e vary minimal amount of ram out.
Wow, sent an e-mail as suggested when clicking on "use classic" banner, and got a fast response that addressed my msg
Did anyone else read the title as "Salvaging DRM"? Hmmm, for minute there I thought answering machines were DRM protected.
Fight Crime - Shoot Back!
Defective hardware is distributed to the nearest geeky friend, i myself have a shelf and a spare desk with drawers full of old/non working hardware. I'm sure you average /. reader has at least this if not a spare room full of old 286 boxes.
"Sic Semper Tyrannosaurus Rex."
Seriously, I've had some of their OEM memory as part of a package deal, and it was very nasty stuff.
What's worse, before they would take it back, they wanted to "test" it, testing being limited to a couple runs of PC-Doctor, which is totally lightweight.
To make a long story short, they refused to take it back the first time, later it blew up my motherboard. They replaced the motherboard (it was part of the package) and sent me home, where I discovered my Athlon XP was also damaged. I took it up there, and they wanted to run PC-Doctor on it, but the "technician" (hah!) cracked the CPU while putting it in a "test board," so "oops, I guess we're replacing that."
P.S. One of the guys at the return desk who I got to know quite well told me, when I asked him why the "test boards" they were using always changed, that he thought they were boards that belonged to customers. Whether that meant boards in for repairs, or returned boards, I don't know or care - either is bad news.
P.P.S. This was at the Fry's in Wilsonville, Oregon. There is also an idiotic troll in the service department there who, after ignoring me waiting at an empty counter for 10 minutes while he chatted on the phone, wanted to charge me for a "missing" monitor stand on a monitor I was returning, refusing for 15 minutes to look in the bottom of the box under the styrofoam because monitor stands always come attached to the monitors, didn't you know? He finally looked when I demanded to talk to the manager, and of course it was there. I had a long discussion with the manager anyway over his, and their, incompetence (I reminded him of the memory fiasco) but the troll was still lurking there the last time I dropped by for consumables, which is all I will ever buy from Fry's, now. You can't miss him - he looks like he'd feel more at home in a raincoat, instead of his cheesy lab coat, roaming a playground on a sunny day.
Get off my launchpad!
...no, I never really did wonder what happened to DRAM that failed the everpresent quality-assurance testing. Never really occured to me. So nyar.
Informatus Technologicus
This is why I stopped using answering machines and started using the voice messaging at the telco. Millions of little plastic boxes eating up electricity in millions of homes is bound to be less efficient than voice messaging at a central server.
The services at the telco let people leave messages when I am on the phone.
Badram requires a simple download, dd to floppy, booting off the floppy, and making sure it started up okay. Then, you can leave it alone for a day while you let it make passes.
Anyways, assuming you are buying new ram and you want to be sure its okay, you'd have to do the same thing. And some older laptops have integrated onboard memory - the badram patch can work around that.
I have a 64M proprietary memory stick for an old toshiba laptop that will be arriving soon in the email - I will be using badram to test that when it comes.
No Most major manufacturers use quality ram.
Compaq and IBM both use Kingston Memory. They also like to jack up prices for their "rebranded" Compaq/IBM ram which is just really a Kingston module with an even higher price.
Toshiba uses Samsung. I'm not sure about manufacturers like Dell or Gateway.
Arriving in the email!!! Wow what will they think of next? No wonder you have problems with it. Your ink jet probably is set to too low of a resolution to print the circuit, for more help on setting up your printer check out linuxprinting.org
Ad Majorem Dei Gloriam
Interested in AI? MACR
I wo~nder when we wil+ see tho&e defec%ive ch)ps in ou! deskt{p mach?nes?
But it's also theoretically possible for any number of other things to break, and spontaneous RAM failure seems very, very low on the list of things to worry about.
Well, the thing about RAM failure is that, unless you do something like ECC, you won't detect the errors until it causes a crash. Probably, you'll lose some data to corruption first. The other thing is that RAM errors can be induced by bad power or other transient problems. Finally, it does happen, so better safe than sorry - you're spending $2k on a server, so why cheap out on a $50 part?
"We returned the General to El Salvador, or maybe Guatemala, it's difficult to tell from 10,000 feet"
What is this "Kingston" memory of which you speak? AFAIK, Kingston does not make ram, they throw other people's die on their modules (and sometimes they just buy the modules whole). It's pretty much a crap-shoot of whether or not you're getting samsung, hynix, micron (who just signed a deal to start selling to them again), or etc. So saying kingston memory is crap would be akin to saying dell makes crappy hard drives...
:-)
Not a flame, just a clarification
Dell uses Micron and Infineon (Siemens) for SDRAM and DDR. For RDRAM I think they mainly use Toshiba. I always recommend Crucial to people because it is just the retail branch of Micron. Lifetime warranty and I've never had a failed stick.
ECC isn't there for the tiny chance that one, and only one, chip on the module would catch fire and die. It's there so that any random "bit rot" (single-bit errors) is caught and corrected before it causes damage. All RAM is susceptable to this; it can be caused by cosmic rays (!) or by radioactive decay (can't remember if it's alpha or beta) of minute quantities of radioisotopes in the chips' substrate. While it will only happen once in every ten years or so on average, it does happen and can cause a system crash. ECC is about reducing the possible risk (it would have to flip 3 bits simultaneously to fool ECC RAM).
That's it. I'm no longer part of Team Sanity.
Sell it all and wait to see what the consumer returns.
I see even classic Slashdot is now pretty much unusable on dial up anymore.