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-   -   Intel Core 2: Is high speed memory worth its price? (http://www.madshrimps.be/vbulletin/f6/intel-core-2-high-speed-memory-worth-its-price-25607/)

jmke 1st August 2006 16:15

Intel Core 2: Is high speed memory worth its price?
 
Does the Intel Core 2 need fast DDR2 memory to perform at its best? In this article we compare different memory speed and timings to provide you with the answer. Read on to find if cheap memory is enough to feed the Conroe

http://www.madshrimps.be/gotoartik.php?articID=472

Rutar 1st August 2006 17:42

What about overclocking? Are there dividers for Core 2 865 boards as well so we can still clock our Allendales through the roof with cheapskate ram?

jmke 1st August 2006 17:47

I don't know for other boards, I975 allows for quite an adjustment range for divider settings http://www.madshrimps.be/articles/In...otke-12981.jpg

Memory Frequency; 333 / 400 / 533 / 667 / 800 Mhz

so with cheap 533 / PC4200 you run run it at 333 and get quite a bit of headroom for overclocking without the memory running out of specifications.

for the newer P965 and older 865 I can only hope there are similar settings, don't know, google ? :)

jmke 1st August 2006 18:45

I've updated the last page with info on the decrease of performance with PC5300 vs PC4200, thanks to Sintel for the clear explanation:

The Core 2 has a front side speed bus (FSB) of 266Mhz x 4 (Quadruple) “1066Mhz”, the ram is running at 266Mhz x2 (Dual Channel) x2 (DDR) = “1066Mhz”, so with PC4200 memory and FSB are running synchronized. When you use PC5300 you are no longer running synchronous with the FSB and a factor of x1.25 has to be used. The older Athlon XP from AMD also displayed this decrease in performance when running memory asynchronous, where memory latency is more important then memory bandwidth; the Core 2 technology is similar in this aspect. With the Pentium 4 the pipe lines were longer and the effect of running asynchronous which increased latency was masked.

By running the memory synchronous to the FSB you have the least amount of latency and thus performance is at its best. Why is PC6400, which is also running asynchronous faster then? Because the memory latency and speed is now that much higher that it compensates for the loss of running asynchronous and overall performance does increase. PC5300 worked great with Pentium 4 but it should be avoided when running Core 2.

jmke 1st August 2006 19:59

it's still a bit more complicated it seems:

http://www.bleedinedge.com/forum/sho...016#post180016

Quote:

Now we need to look at memory ratios.

In 800 strap we have the following ram ratios.

400,533,667,800 or as some quote them 1:1, 3:4, 3:5, 1:2

In 1066 strap we see the following.

400, 533, 667, 800 but the actual ratios have altered, 400 mode is now a down clock so the following applies.

400=4:3, 533=1:1, 667=4:5, 800=4:6

Moving to 1333 strap we see another change.

400= 5:3, 533=5:4, 667=1:1, 800=5:6
as the SYNC changes if you set a higher strap

impar 2nd August 2006 11:18

Greetings!

How can you say that the reason is the synchronicity between the RAM and the FSB, if you only tested one FSB?

jmke 2nd August 2006 11:34

if you read through the complete text of the forum post linked above, you'll see that by changing the CPU native FSB and thereby also the north bridge strap, you shift the 1:1 sync from 400 to 533 to 667; but even at 667/1333(FSB) the performance is lower, when running in sync, as the NB is running on higher latency to obtain this speed, thereby decreasing performance.

if you CAN change the NB strap, you can alter the NB strap setting, forcing it to run either slower/faster to give you more headroom for overclocking, but that something for a different article. :)

Xploited Titan 2nd August 2006 23:18

mmm, I ordered my Core 2 Duo which will arrive second half of August.

I ordered 2GB dual channel G.Skill memory DDR2-800. I took that due to the timings offered (4-4-4-12) at that speed AND it being the lowest priced (near 180€).

Was that a good move? Or was there something better to be bought? If I could clock down the timings to something like 3-3-3-8, would it be interesting enough to try it, or just a waste of time?

jmke 3rd August 2006 08:17

if you are planning to overclock, the headroom of the DDR2-800 will allow you to run 1:1 while you increase the FSB

impar 3rd August 2006 10:11

Greetings!

But then, how to explain the weird behaviour of Quake4?
The performance at 800*600 rises with faster memory, regardless of being 1:1 or not.


From the article:
Quote:

The older Athlon XP from AMD also displayed this decrease in performance when running memory asynchronous...
The synchronicity feature on Athlon XPs applied only to nForce2, not VIAs chipsets.
So, other C2D chipsets may show a different behaviour, no?


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