Memory Frequency

[Nikolai]

Hi guys,
Im trying to understand memory a little better, am I correct in saying that in comparison between Corsair DDR2 RAM:
Dominator PC2-85o0(4GB pack, 4x1GB).. so 4 x 1.06GHz Ram = 4.24GHz (totalled)

Twin2 PC2-6400(4GB pack 2x2GB) so 4 x 0.8GHz = 3.2GHz

And so comparing these two, the top one (dominator) is approx 33% faster then the twin2 .... ?
Is this the correct way to work out the working speeds of Ram and there comparison in speeds?

[Yellowhello]

Yes, the Dominators are faster, but i'm not sure that's how you figure out the speed.............

EDIT: Usually, the frequency in MHz is also listed. (i.e. 800MHz, 667MHz, etc.) The higher the frequency, the faster the RAM. Also, there are the timings (i.e. 5-5-5-15, 4-4-4-12, etc.). The lower the timings, the faster the RAM. I don't really know about the PC2 stuff.

[[Dr. V]]

Yessir you definitely are.

1.06GHz is the speed of the memory. This is NOT combined. It's just like CPUs with more than one core - the speeds (GHz) are NOT added up. The only thing that's added up with multiple RAM sticks is the QUANTITY (in this case GB) of total RAM. 4 x 1GB = 4GB. Each stick is rated at 1066MHz (1.066GHz), and that's what they will all run at together - SPEED is NEVER added!

The frequency of RAM is how often the computer (essentially the motherboard) can access the RAM in a given amount of time (the Timing or CAS Latency of the RAM). For example, memory that is rated at 1066MHz with a CAS Latency of 5 can be accessed 1066 times in 5ms (yes, timings are in milliseconds). Also, there is a total of 4GB that can be accessed in your case. So, the motherboard can access the RAM [FREQUENCY] times in [CAS LATENCY] milliseconds with a total of [TOTAL QUANTITY] of RAM that can be accessed.

Understanding a bit better now?

[Nikolai]

Hi, thanks for your reply ...
both of those setups i listed have 4gb of RAM so there is no difference in Gigabytes .... there question was more aimed at the speed of the ram, i was listing the frequency of the RAM, such as 0.8ghz .. or 800mhz ... and seeing how they add up when put in a group of 4gb .... compared to 4gb of RAM set at 1.06ghz ... and seeing if the mathematical difference in ghz correlated with the speed differential in real practice ?
or is this just an obvious thing i am asking and cant see myself?

[[Dr. V]]

There is most definitely a difference. Read over my post as many times as you need to understand.

[Nikolai]

ahhh ok, thanks stix .... i get it now ... so basically the speed differential between 4gb of 0.8ghz ram and 4gb of 1.066ghz RAM is the difference of more like 25% gain in speed .... as you go up from 0.8 to 1.066?

[[Dr. V]]

Exactly. That's just looking at the MHz. To know the true difference you'd need to compare the difference of timings as well. For example.

If you can access 4GB of ram 800 times in 4ms, how does that compare to being able to access 4GB of ram 1066 times in 5ms?

See what I mean?

[sean126]

Nikolai,

When I was testing my memory for stability, I was testing with different Mhz and different timings...ie...4-4-4-12 vs. 5-5-5-15 and such.

I don't game, all I do is video stuff and back up dvd's. The results that I got (I don't know how good they are) showed that the tighter timings (4-4-4-12) vs. more relaxed ones...5-5-5-15 helped speed things up a bit as opposed to higher MHz. By a bit I mean 30 seconds to 1 minute in DVD encoding.

I don't know how it works out for gaming, but I think Higher Mhz makes more of difference...but I'm just guessing.

[Nikolai]

yeh im using this more for photoshopping large files ... sometimes at work we get files up to 2gigs in size and the workflow slows down dramatically.
I guess im trying to avoid this but dont want to spend twice as much on RAM that only give me 25% more power then the frequency below.

What sort of timings would be best for this sort of work do you think?

[sean126]

I'm an idiot compared to some of these guys....but an idiot's opinion is: I believe its a combination of your cpu and memory. If I'm right in assuming that the image rendering times will be a matter of seconds, I'd say look at the deals on ddr2 6400-800Mhz with 4-4-4-12 (or 15) timings. I know OCZ's platinum revision 2 worked out good for me and they always have good deals on 2 gigs (1 gig x2). I got mine for about 80 bucks after a rebate.