Info on ram...

[BestNzWrestler]

Hey,

Im just wondering whats the difference between ECC and Non ECC ram? because im considering buying some more...

and this is what i have found...

512MB Transcend PC133 JetRAM(168-pin Non-ECC CL3 SDRAM) Transcend $119.00

and

512MB Transcend PC133 ECC Registered 168-pin CL3 SDRAM, Low Profile Transcend $282.00

Apart from the difference in price, what is the difference?

Thanks

 

[Fox Mulder]

ECC stands for Error Correcting Code and does just what it sounds like it does, detects and fixes errors in memory data. If your motherboard supports the use of ECC memory it's probably a good idea to use it. But this is only needed if you have tons of ram in your system and especially needed if you do multitasking a lot. ECC slows down performace of your ram by 2 to 5%.
Servers generally use this type of ram. So, if you are only a gamer you can stick with Non-ECC because its cheaper. But ECC ram corrects 95% of all errors that ram will eventually get.
It will correct 1 bit errors, which when ram fails (95% of the time) that is what makes it fail. So you have to weigh the benefits; with the price of ram right now, benefit is low; but when ram was more expensive the loss of speed by the ram fixing the error probably saved people the cost of buying new ram.

 

[LTR12101B]

ECC is the modern replacement for "parity" - back when simms were 8/9 bit, the extra bit was used for parity (if present, supported and enabled) - and had the effect of halting the system with a scary message in the event of a memory error being detected (instead of continuing, and possibly corrupting data).

It fell out of favour, as particularly with the trend to 2 chip = 8 bit simms, the addition of a 1 bit extra chip for parity raised the cost.

With ECC, ALL 1 bit errors (systematic or random) can be corrected, and some higher level errors are correctable, or if uncorrectable, detectable.
IS it actually slower? - not sure


The main point is that using GOOD memory, and checking it with test programs and the BIOS scan, should keep you aware of systematic (BAD) memory errors, leaving only the random errors (eg. Alpha particle induced) to worry about - and the trend to larger memory increases the statistical risk of random errors.


NB. If you wish to use ECC, ALL the RAM in your system must be ECC, so if you already have ECC memory in and supported, always add ECC. If you have an ECC-supporting system but do not have ECC memory already, then to upgrade to ECC, you have to replace the existing memory with ECC.


The other important statistics for memory are the CL (2, 2.5, 3), the not usually mentioned Trc delay, and some motherboards are sensitive to banking issues (mine will NOT accept single-banked 256Mb modules)

PS. Some systems recommend/require "registered" RAM above certain module sizes - check your motherboard manual!