DDR2 Ram Question

bigboab5 · 15-07-2008, 19:41

Just a quickie guys.

gonna buy some ram, and I want to know if the "PC2" bit of "1GB DDR2 800 PC2-6400" means that it is Dual channel?

Thanks

Bigboab

boroboi · 15-07-2008, 19:51

the 2 means its just 2nd generation. Most RAM these days is dual channel, however you must make sure it states that in the specs also.

**Kymmy** · 15-07-2008, 19:52

Dual rate or dual channel???

DDR2 ram transmits twice as much data per clock cycle than DDR ram, where as dual channel is the motherboards ability to treat two ram sticks as one hence doubling the throughput then single channel.

Kymmy

Wicked_and_Crazy · 15-07-2008, 19:59

I think PC2 refers to the fact that its two sided.

I thought Dual channel was just a mobo thing to double memory bandwidth by adding a parallel memory channel so that the CPU had twice as much memory bandwidth avaialble as memory technology wasnt advancing as quick as CPU technology and the CPU's were being throttle by bottlenecked memory

boroboi · 15-07-2008, 20:13

You can get double sided DDR1 RAM.

The "2" in PC2 means exactly the same as the "2" in DDR2, it states that the RAM is 2nd generation, as opposed to being DDR or DDR3. You'll notice DDR is PC ram, DDR2 is PC2 and DDR3 is PC3.

Tripple channel memory isnt on the market until Nehalem is commercialisd.

bigboab5 · 15-07-2008, 20:24

hmmm, now I'm more confused. I see advertised the following DDR2 memory

4763 512MB DDR2 667 PC-5300. . . . . . . . . . . . . . . . . . . . . £12.00
4311 1GB DDR2 667 PC2-5300 . . . . . . . . . . . . . . . . . . . . . . £14.00
4244 1GB DDR2 800 PC2-6400 . . . . . . . . . . . . . . . . . . . . . . £14.00
two says PC2, one don't

My motherboard supports

4x 240-pin DIMM slots support maximum memory capacity up to 8GB
Supports Dual Channel DDR2 800/667/533 Un-buffered Non-ECC memory.

So...... what do I go for?

boroboi · 15-07-2008, 20:30

It's probably a mistake, all DDR2 memory is PC2.

The RAM will have to actually say it is dual channel RAM in the discription.

The two sticks are usually matched and come in dual channel kits, and its not reccomended to buy two sticks that arent matched and run them in dual channel. It sometimes works, but often doesnt.

If it comes with one stick, then its not dual channel RAM, it needs a matched sister chip... so you'll be looking for something that says 2x1GB, or 2x512MB or whatever size you're looking for

**David F** · 15-07-2008, 20:34

buy the 800 then. link to the site your gonna buy from

bigboab5 · 15-07-2008, 20:38

Quote:

Originally Posted by David F

buy the 800 then. link to the site your gonna buy from

http://www.pless.co.uk/home.php?cat=120

though i got the price from the in-storeprice list as listed on the right. Its a local shop that I can buy from and do often.

boroboi · 15-07-2008, 20:41

So according to that site, the cheapest you're going to get dual channel memory is the 800mhz OCZ REAPER 2x1GB kit for 71.99

altis · 15-07-2008, 20:42

http://en.wikipedia.org/wiki/DDR2_SDRAM

**David F** · 15-07-2008, 20:45

they do not really have much choice http://www.overclockers.co.uk/showpr...(GX22GB6400UDC)

Alien · 15-07-2008, 21:12

Quote:

Originally Posted by David F

they do not really have much choice http://www.overclockers.co.uk/showpr...(GX22GB6400UDC)

How much commision do you get per sale?

I have the same ones [as does Dilli, IIRC].

**David F** · 15-07-2008, 21:30

you know me and OCUK are not on best of terms but that ram is good value maybe cheaper if the OP shops around though

Matth · 15-07-2008, 21:50

If you buy 2 sticks at the same time, it is likely that they will dual up ok, a lot of places say they will pair them, even when it's generic.

eg.
http://www.7dayshop.com/catalog/prod...ucts_id=102277

DDR2 800Mhz (PC2-6400) - 1GB - £9.99 - will be dispatched as matching pairs in quantities of 2 or greater
So it's generic, brand unspecified, but supplied in pairs - there is nothing special about "dual channel RAM", other than it being supplied as packaged pairs.

PS. If you have dual channel, and your CPU is 1333FSB, then setting the RAM to DDR2-667 speeds and tighter timings may lower latency, similarly for a 1066 FSB CPU, possibly DDR2-533 - in general, it should be possible to lower the memory speed and pull the timings in by 1, and with RAM capable of higher speeds, performance in both setups can be compared, with the RAM at the highest speed, or with dual channel RAM working at half-synchronous speed - it really depends how well the chipset handles speed buffering.

AMDs operate differently, and will use a divisor that brings the memory to rated speed or as close as possible below, though some AMD clock speeds cannot deliver full memory speed due to the integer divisor limitations - AMDs on steps of 400MHz will run DDR2-800 at full speed, the inbetween steps will not.