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#1
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Memory confusion or confused about memory.
Hi,
I'm looking at memory for the opteron, and ran across this at one vendors web site. ECC+registered memory Registered memory only What is the difference? I thought that all Registered memory was ECC. Could be the vendors web site is wrong or I don't really understand what is registered memory. Did some searching on google but nothing came up to clear the matter. Thanks for any info. Alan |
#2
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Well some more searching and found the answer. Really adding some good
key words. I was getting tons of memory for sale at first. What is meant by Registered memory? "Registered" is a means of "Buffering" the memory in SDRAM. This means that the clock signal is boosted across the entire array of memory chips so that the computer sees a clean sharp clock signal instead of a weakening clock signal as it progresses along the length of the memory path. Registered memory must be supported by the system board and cannot be mixed with "Unbuffered" modules. You must have only Registered memory to use Registered memory. This is a further means of eliminating the possibility of errors when reading the data in memory and is used when the data returned from memory is extremely critical, such as in scientific or financial calculations where the integrity of the data is CRITICAL. It also allows a module to be built using more chips, allowing for larger capacity modules to be made. ************************************************** * Therefore I see that registered is different from ECC+registered. Anyway why do the opteron/athlon64 boards require registered and/or ECC+registered memory? Thanks "Spam" == Spam Me Please writes: Spam Hi, I'm looking at memory for the opteron, and ran across this Spam at one vendors web site. Spam ECC+registered memory Registered memory only Spam What is the difference? I thought that all Registered memory Spam was ECC. Spam Could be the vendors web site is wrong or I don't really Spam understand what is registered memory. Did some searching on Spam google but nothing came up to clear the matter. Spam Thanks for any info. Spam Alan |
#3
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"Spam Me Please" wrote in message
... Therefore I see that registered is different from ECC+registered. Anyway why do the opteron/athlon64 boards require registered and/or ECC+registered memory? Actually, it's only the Opteron and Athlon 64FX that requires it, but not the regular Athlon 64. The reason the Opt/A64FX require registered memory is because they are the same chip, an A64FX is just a renamed Opteron 100-series. Since the Opterons are server chips, they need to be able hold a lot of memory modules, so it needs to be registered memory. If it weren't registered then these processors couldn't hold much more than two or three memory modules before their signal got all wonky. Why ECC memory? For the same reason as why registered memory, these chips have their background in server systems, where reliability is most important. Yousuf Khan |
#4
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Thanks for the information. Actually a better explanation than what I found on google. Interesting the Athlon 64 can use either ECC or Non-ECC unbuffered memory. At the least the boards that I have looked at. I guess it does not make much difference for a small office server. Thanks "Yousuf" == Yousuf Khan writes: Yousuf "Spam Me Please" wrote in message Yousuf ... Therefore I see that registered is different from ECC+registered. Anyway why do the opteron/athlon64 boards require registered and/or ECC+registered memory? Yousuf Actually, it's only the Opteron and Athlon 64FX that requires Yousuf it, but not the regular Athlon 64. The reason the Opt/A64FX Yousuf require registered memory is because they are the same chip, Yousuf an A64FX is just a renamed Opteron 100-series. Since the Yousuf Opterons are server chips, they need to be able hold a lot of Yousuf memory modules, so it needs to be registered memory. If it Yousuf weren't registered then these processors couldn't hold much Yousuf more than two or three memory modules before their signal got Yousuf all wonky. Yousuf Why ECC memory? For the same reason as why registered memory, Yousuf these chips have their background in server systems, where Yousuf reliability is most important. Yousuf Yousuf Khan |
#5
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On Wed, 22 Oct 2003 20:23:06 -0500, Spam Me Please
wrote: snip Therefore I see that registered is different from ECC+registered. Yup. It is possible to get non-ECC registered memory, but that stuff is REALLY rare. Besides which ECC is a GOOD thing to have, so just stick with the registered ECC memory. Anyway why do the opteron/athlon64 boards require registered and/or ECC+registered memory? Athlon64 does not require registered memory, the Opteron and the Athlon64 FX do. The reason has to do with a combination of the target market and expected memory configuration of the Opteron vs. the Athlon64. The first thing to point is the reason why you would use registered memory. SDRAM and DDR SDRAM use a memory bus, so all chips on the bus are connected together. In your typical memory module you have 8 or 16 memory chips. Now put 3 or 4 memory modules on the same bus and you can easily get up around 50+ chips on the same bus. Each one of these chips requires a little bit of current for it's clock, and if you start getting up beyond about 32 chips on the bus, it quickly becomes impossible to provide that much current. What's worse, the more current draw you have, the "dirtier" your signal becomes, leading to potential memory errors (= BAD!). As memory speeds have become higher, this has become harder and harder to deal with. So, rather than doing this, you use registered memory. So now, instead of sending the signals to each individual memory chip, you send them to a single buffer chip on the module. So, with 4 modules on your memory bus, you now have only 4 chips to send signals to instead of 50+ chips. Obviously if you only have a single module or even two modules on the bus, registered memory isn't really needed, but if you're going to put a lot of memory in the system, it quickly becomes a requirement. So, that brings up back to the target market. Opteron is targeted at the server and high-end workstation market, where lots of memory is common. Ideally the Opteron might have been designed where you could put only two unregistered modules in the system or use registered modules if you wanted more memory, but this may not have been an option. As such, AMD made the trade-off to allow more memory (good thing) but required registered memory. Similarly most Intel Xeon motherboards require registered memory. With the Athlon64 you are looking at a desktop processor, designed for relatively small amounts of memory. As such, AMD designed it to use the cheaper unregistered memory. The Athlon64 FX is a bit of an odd-ball here. This chip is actually just an Opteron processor that is being rebadged and marketed as a desktop processor. Nothing really wrong with this, but as an Opteron chip, it requires registered memory for the time being. It is expected that AMD will change the design of the Athlon64 FX to allow for unregistered memory in the relatively near (next 6 months?) future. In doing so though, the new Athlon64 FX chips (currently referred to as "Socket 939" models, due to the new socket they are expected to use) will not be compatible with current boards. A quick note about ECC. With Intel's i865 and i875 chipsets, as well as AMD's new Athlon64 and Opteron chips, ECC is supported by most systems these days (unfortunately most AthlonXP motherboards do not support it). ECC is a GOOD THING! It will detect and correct soft memory errors. With new systems coming with more and more memory, soft memory errors are becoming more common. According to a rather extensive study by IBM, with 256MB of memory you can expect 1 soft memory per month. With 512MB of memory, as is common on most systems today, soft memory errors will happen more often, and with 1GB of memory as many new systems come equipped with, they are likely to happen every week or two. Now, you might get lucky most of the time and these soft memory errors won't affect anything. For example, they might just turn a single pixel on your screen a different colour for a moment or two until it's redrawn, or it could even be in an unused portion of memory. However, the error could also happen in a bit of the operating system, causing the system to become unstable. Worse yet, it could happen in an important piece of data, causing you to get incorrect data for something that needs accuracy. Point being, these days I would highly recommend ECC memory, regardless of whether you are looking for a system that needs registered memory or not. ------------- Tony Hill hilla underscore 20 at yahoo dot ca |
#6
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Wow that was a good read. It looks like the tide is turning for a good reason to purchase ECC memory. I can remember some years back were the consensus was that ECC was a waste of money because of the low bit error rate (well that is what some self proclaimed experts said). It is very interesting to me what you said about memory errors because I have an old ppro dual motherboard that reports memory errors in the bios, and it usually has one or two errors over a 3-4 month period. I guess if anyone goes to the trouble to backup their data, which I do, they probably want to consider ECC. Glad you posted that information because looking at the price of ECC vs Non-ECC the difference is only 20 bucks for one gig of memory. At least the brand I was looking at. That is for non-buffered ECC memory. Registered ECC memory costs a lot. Well anything with the name server on it costs a lot probably for good reasons. Thanks for the information. "Tony" == Tony Hill writes: snip major snip |
#7
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On Fri, 24 Oct 2003 00:29:28 GMT, Tony Hill
wrote: A quick note about ECC. With Intel's i865 and i875 chipsets, as well as AMD's new Athlon64 and Opteron chips, ECC is supported by most systems these days (unfortunately most AthlonXP motherboards do not support it). The 875 chip set does support ECC, but the 865 does not. See page 19 of the datasheet: ftp://download.intel.com/design/chip...s/25252303.pdf ECC is a GOOD THING! It will detect and correct soft memory errors. With new systems coming with more and more memory, soft memory errors are becoming more common. According to a rather extensive study by IBM, with 256MB of memory you can expect 1 soft memory per month. With 512MB of memory, as is common on most systems today, soft memory errors will happen more often, and with 1GB of memory as many new systems come equipped with, they are likely to happen every week or two. Now, you might get lucky most of the time and these soft memory errors won't affect anything. For example, they might just turn a single pixel on your screen a different colour for a moment or two until it's redrawn, or it could even be in an unused portion of memory. However, the error could also happen in a bit of the operating system, causing the system to become unstable. Worse yet, it could happen in an important piece of data, causing you to get incorrect data for something that needs accuracy. Point being, these days I would highly recommend ECC memory, regardless of whether you are looking for a system that needs registered memory or not. I think the IBM claim is overstated. In my own experience using ECC systems where the BIOS would log errors, memory errors were very rare (perhaps one every two or three years). Still, if the board supported ECC I'd definitely use it. - - Gary L. Reply to the newsgroup only |
#8
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"Spam Me Please" wrote in message
... Wow that was a good read. It looks like the tide is turning for a good reason to purchase ECC memory. I can remember some years back were the consensus was that ECC was a waste of money because of the low bit error rate (well that is what some self proclaimed experts said). Back then "some years back", people weren't routinely running a half a gig of memory on their home machines. Now they are, so it's a good idea to have it. Also back then they weren't really using ECC memory, they were using what is called parity memory. Parity is a less sophisticated form of ECC: it could report errors but not correct them. Yousuf Khan |
#9
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On Thu, 23 Oct 2003 21:24:59 -0700, Gary L. wrote:
On Fri, 24 Oct 2003 00:29:28 GMT, Tony Hill wrote: A quick note about ECC. With Intel's i865 and i875 chipsets, as well as AMD's new Athlon64 and Opteron chips, ECC is supported by most systems these days (unfortunately most AthlonXP motherboards do not support it). The 875 chip set does support ECC, but the 865 does not. See page 19 of the datasheet: ftp://download.intel.com/design/chip...s/25252303.pdf Hmm, that's rather interesting, considering that the i875 and i865 are the same silicon just with different settings. I guess Intel disables ECC support on the i865 as one of the ways to segment their chipset market. Point being, these days I would highly recommend ECC memory, regardless of whether you are looking for a system that needs registered memory or not. I think the IBM claim is overstated. In my own experience using ECC systems where the BIOS would log errors, memory errors were very rare (perhaps one every two or three years). Still, if the board supported ECC I'd definitely use it. The claims may be somewhat exaggerated, but I don't think that they are by very much. Unfortunately memory manufacturers no longer seem to document their soft error rate for memory chips, but even assuming improvements over the old numbers, with 512MB or 1GB of memory, I would be surprised if soft memory errors didn't occur on a semi-regular basis. Of course, there are a lot of things that will affect the error rate, so it's tough to pin down a single number, but I still feel that it's worthwhile to get ECC memory these days. ------------- Tony Hill hilla underscore 20 at yahoo dot ca |
#10
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