RAM stats

hypochondriac · 23 Jul 2008 at 20:49

Ok so I know what the RAM memory size is, and i think I know what DDR2/3 etc is, but can someone breifly explain in laymans what the other bits mean like 800Hz, 5-5-5-12, and PC2-6400C4 mean please?

BFG_9000 · 23 Jul 2008 at 20:51

I asked the same question on this forum link: http://forums.overclockers.co.uk/showthread.php?t=17899685 don't think anyone knows by the response..... * any memory experts out there*

Craig321 · 23 Jul 2008 at 20:53

http://en.wikipedia.org/wiki/SDRAM_latency

hypochondriac · 23 Jul 2008 at 21:01

well that clears the timings up, but what of the frequencies?
Also is performance heavily depended on these stats? ie will getting 1066MHz be a noticable improvement over 800MHz?

Pneumonic · 23 Jul 2008 at 21:46

ok well depending on your motherboard and chipset the RAM runs in different ways either linked or unlinked from the Front Side Bus (FSB)... Now am going to explain this easy so forgive me if you know this... the FSB is like the highway of communication on your motherboard between your CPU and RAM... The FSB determins the speed the CPU runs at and on a linked motherboard the speed the RAM runs at...

So for example

CPU speed is a factor of the FSB and its multiplier so 400FSB * 8 multiplier on a CPU would give 3200mhz on the CPU

On a linked motherboard (like the p35/45 x38/48 chipsets) your RAM is also linked to the FSB so... its frequency (or speed) is a multiplier of the RAM divider and FSB so for instance on a divider of 2 on the above clock the frequency is 800mhz on a divider of 2.4 the frequency would be 960mhz..

Now RAM has two rating effectivly the timmings i.e. 4-4-4-12 and the frequency.. each type of RAM is rated at a different frequency.. so PC6400 is rated at 800Mhz PC8500 at 1066mhz etc..

In terms of performance you generally sacrifice timmings to gain frequency... i.e. PC6400 RAM rated at 4-4-4-12 may well do 1066mhz at 5-5-5-18 in the same way PC8500 rated at 5-5-5-15 / 1066mhz will do 4-4-4-12 at 800mhz... so all your really doing when buying PC8500 for example is buying the fact it will do 1066mhz where as PC6400 might do 1066mhz

hope that helps

reflux · 25 Jul 2008 at 14:04

Re: latencies VS. speed, in AMD systems you tend to get better performance from running lower latencies, which has something to do with the CPU having an integrated memory controller. With Intels, and specifically the quads, you're better off running the memory as fast as you can because the CPUs love the extra bandwidth. That said, I wouldn't go for ram with latencies higher than 5-5-5-18 @ 1100mhz or thereabouts as the bandwidth benefit starts to disappear.