2 GB of PC3200 Question

[NumenorLord]

If I want to get a new computer with 2 GB of memory, would it be better to get 4x512 mb @ 2-3-2-6 or 2x1 GB @ 2-3-3-6? I've heard some concerns over 4 sticks of memory, but would the faster timings negate that?

 

[gudodayn]

No, faster timing with 4 sticks is allowed because the modules are at 2T and not 1T.
With a drop from 1T to 2T, you will be penalized on the overall bandwidth of your modules.
My trials with such module configurations are as follow:

In dual channel (4 populated dimms - 512MB x 4 @ 2T, 2.5-3-3-7), my bandwidth is around 4800MB/sec, this equals to around 75% efficiency of the total bandwidth (DDR400 PC3200 x 2 = 6400MB/sec)
On a loan from a friend with 2 x 1GB sticks also at CL2.5, 2.5-3-3-7 but at 1T, my bandwidth is around 5800MB/sec. This equals to about 90% efficiency of the total bandwidth (6400MB/sec)

As you can see from the result, Cas Latencies aside, bandwidth difference between 1T (2 sticks in dual channel) and 2T (4 sticks in dual channel) is about 1000MB/sec.

As for real world differences, I didnt notice too much.
I was thinking of going to 4 x 1GB in dual channel, refer to my other post......http://forumz.tomshardware.com/hardware/modules.php?name=Forums&file=viewtopic&t=180198&highlight=

Hope this helps with your purchase decision!!

 

[NumenorLord]

Wait, so the 1 GB sticks are faster because they're 1T (not sure what that means), if I understand correctly? So at the same cost, I should go for the 2x1 GB sticks? I guess they have more bandwidth, right?

 

[gudodayn]

Right!!!
2x 1GB stick will run at 1T in dual channel confiuration but with 4 sticks, it will only run in 2T so.......
1T > 2T. Most people prefer to have 2 x 1GB sticks if its within their budget.

My upgrade was just to add another two 512MB sticks to make it 2GB because my budget didnt allow me to buy 2 x 1GB at the time.

But it seems like you have an option here....definitely go with 2 x 1GB configuration. You can always upgrade to 4 x 1GB sticks when VIsta is released and if there is a need for such memory capacities.

 

[chocobocorey]

how do you know if your ram runs at 1T or 2T? i have 2x1GB of g.skill pc3200.

 

[TabrisDarkPeace]

No, faster timing with 4 sticks is allowed because the modules are at 2T and not 1T.
With a drop from 1T to 2T, you will be penalized on the overall bandwidth of your modules.
My trials with such module configurations are as follow:

In dual channel (4 populated dimms - 512MB x 4 @ 2T, 2.5-3-3-7), my bandwidth is around 4800MB/sec, this equals to around 75% efficiency of the total bandwidth (DDR400 PC3200 x 2 = 6400MB/sec)
On a loan from a friend with 2 x 1GB sticks also at CL2.5, 2.5-3-3-7 but at 1T, my bandwidth is around 5800MB/sec. This equals to about 90% efficiency of the total bandwidth (6400MB/sec)

As you can see from the result, Cas Latencies aside, bandwidth difference between 1T (2 sticks in dual channel) and 2T (4 sticks in dual channel) is about 1000MB/sec.

As for real world differences, I didnt notice too much.
I was thinking of going to 4 x 1GB in dual channel, refer to my other post......http://forumz.tomshardware.com/hardware/modules.php?name=Forums&file=viewtopic&t=180198&highlight=

Hope this helps with your purchase decision!!

That is because the SANDRA memory test only works with 4 to 16 byte reads, if it read data in 128+ byte chunks the overheads wouldn't take 25% of the bus traffic.

Needless to say, most applications will have their code & data prefetched these days during execution, making it less important, but still a test people can learn from.

The 1T vs 2T (CMD RATE) difference has nothing to do with the modules at all, it is purely a memory controller configuration setting.

With 4 ranks (would could be just 2 x dual-rank DIMMs) there is a chance that 2T CMD RATE will be used. With more than 4 ranks 2T CMD RATE is required.

http://www.amd.com - They invented the memory controller in the CPU that is being configured with 1T or 2T CMD RATE, suggest checking there to see why it is required in some configurations.

 

[backatu]

how much faster are 2 x 1gb compared to 4 x 512mb?

 

[TabrisDarkPeace]

Up to +20% faster when performing heaps of small reads.

However, due to prefetching, write combining, and the fact that most reads to memory are 128 bytes or more, the overheads become a smaller and smaller percentage.

In real-life applications, it would only be +5% faster, if that.

If you can get 4 x single rank modules, each 512 MB in size, then you can run the memory controller (which is in the CPU) at 1T CMD RATE anyway, even with 4 x DIMMs.

I'd strongly suggest getting 2 x 1024 MB PC3200 now, then just adding in another two 12 months after Vista comes out. Plan for it, save $1/day to do it.

 

[NumenorLord]

Well I guess I shouldn't have asked about DDR 400. What about DDR2 533 though (PC 4200). Would it be the same deal? If I have 1 GB (2x512 mb) right now, it would still be a lot faster with 4x512 mb of memory right?

Also, would my P4 630 @ 3.0 GHz bottleneck say a 7900 GT?