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ECC

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July 2, 2002 8:21:08 AM

I am getting a 512 MB DDR/333 MHz RAM and I have the option of getting ECC with it (Error Correction Code). What is it and is it worth getting? Thanks

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July 2, 2002 1:30:11 PM

If you wan to spend the extra couple of buck go ahead. If you need operational stability at all times buy it. It will eliminate most one bit errors. So if you are running a server, network, or just want your system to never crash due to the most commom type of memory errors go and buy it. If not it will not really help you.

<b>"Sometimes you can't hear me because I'm talking in parenthesis" - Steven Wright</b> :lol: 
July 2, 2002 8:26:17 PM

I think that ECC memory modules also are registered (buffered) and many mobos only support unbuffered memory. But Im not sure. You should verify this.

Further, Im very certain that ECC reduce memory performance. The memory module is 64 bits wide and the ECC code is 8 bit. If the ECC is used (as the name implies) for CORRECTION (and not just detection) the ECC code must be calculated over the entire 64 bits data. So if some memory operation needs to write 32, 16 or any other different from 64 bits, the memory controller needs to perform a read-modify-write in order to recalculate the ECC code. This is something I speculate from my knowledge of error correcting codes. I have never seen a memory benchmark comparing ECC with non-ECC memory.

In contrast if only detection is used, 1 parity bit can be assigned to each 8 data bit. This can only be used for detection since 1 parity bit does not contain enough information for correction.
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July 3, 2002 6:25:47 PM

You can get <A HREF="http://www.crucial.com/store/PartSpecs.asp?imodule=CT64..." target="_new">Unbuffered ECC modules</A>. Now this is only PC2100 but you get the idea.

The differences are slim. So if you want ECC or not is more of an operational stability want more than a performance issue. ECC is slower, but not much.

<b>"Sometimes you can't hear me because I'm talking in parenthesis" - Steven Wright</b> :lol: 
July 3, 2002 7:33:23 PM

make sure your mobo supports it and that you want it. ecc corrects small errors on the fly that it sees in the ram.

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July 4, 2002 3:38:55 PM

Bum_JCRules: What is you source regarding ECC performance? I would expect the impact to have much greater impact than the difference between CAS2 and 2.5 which everybody is so conserned about. Also note that a RAM benchmark which only performs 64 bit writes will give ECC and non-ECC the same score (unless the memory controller is stupid and performs read-modify-write regardless of access size)
July 5, 2002 1:24:21 AM

you dont need ECC
for 99.9% of home users its a waste. costs too much and has less performance.

just get some decent brand name DDR ram like Sambsung, crucial or corsair.

So I fixed my BIG PC problem by pressing the reset button. I'm not a moron am i? :lol: 
July 5, 2002 1:12:46 PM

Since we are here at Tom's Hardware I thought I should use one of their articles. There are plenty of others stating similar results. ECC only slows down a system minimally. You could see higher percentages with older slower systems. (P66-P133, K6-2, Cyrix, or even back to Pentiums that were outsourced to AMD and other manufacturers to build, etc.)

<A HREF="http://www6.tomshardware.com/howto/01q3/010725/bios_tun..." target="_new">"It is possible to boost performance by a whole 1 percent by disabling the "ECC Checking" switch in the BIOS. In doing so, the data flow is no longer permanently supplemented with a checksum, whose function costs additional time."</A> (This article is a year old. So the results on faster systems should be lower.)

<b>"Sometimes you can't hear me because I'm talking in parenthesis" - Steven Wright</b> :lol: 
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