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Dual channel with pc3200 and pc300

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Cowboy X

Cowboy X

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Joined
Oct 12, 2001
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I should be getting a cas2 512mb Corsair 3200 stick to go in a Asus nforce2 board . I only got one due to price . I have a 256 mb pc3000 cas2 stick as well . Can I run them in dual channel mode together at ddr 333 or even at ddr 400 ( reduced cas settings ) ? Or is it that the memory must be identical and the same size as well ?
 
I think you could though you might have a bit of a problem. the only thing I see is that you mght only use 256 of that 512 stiuck you ordered. that is due to the dual ddr? I don't know though maybe someone who has an nforce 2 will be able to let you know.
 
You're only as fast as your slowest stick.

And you MIGHT only use 256 megs of that 512, not sure about that.

Now are you planning to be running onboard graphics? I hope you are because there isn't a single AthlonXP on the planet that will use DualDDR400, not even DualDDR333. A P4's effective 533 bus is filled with DualDDR266.

Even if you get up to 200fsb, a single stick of PC3200 will still fill up your bus. Hmmmm, on a double pumped Athlon bus, to actually USE DualDDR400 (without onboard graphics) would take a bus speed of 400Mhz!!!

Conclusion: save your money :D

*thinks of applying for the position of the Forum's official "Person who tells people not to run their memory faster than their Athlon's fsb"* :D
 
Stumpjumper: I've never understood why people would run their RAM faster than the FSB.

Anyway, I've got two sticks of 256mb PC2100 that'll do pretty aggressive timings at pretty good speeds. I realize that DualDDR is not completely mature yet, but 512mb of pc3200 would cost almost $200, whereas I could get an nForce2 mobo for ~$120. I'd like to run a high FSB, so would running my two PC2100 sticks actually give it more bandwidth than PC3200? I haven't seen any comparative benchies on the stuff. It would be much more cost-effective for me to go with the motherboard if I could actually run my Athlon at 200+ bus speeds by just using the RAM I have in DualDDR.

Oh yeah, when you're running in DualDDR, does your RAM get cut in half? Probably a stupid question, but would my 512 be an effective 256?
 
No no no, don't worry :D

You'll still have all the storage space with the RAM, I was just saying before that I didn't know what would happen if you paired a 512mb and a 256mb.

As for the cost effectiveness, lets think....

A DualDDR setup of PC2100 would equal PC4200 in theoretical bandwidth. Now I don't know how your memory is for overclocking, but to keep it in spec at PC2100, that's a memory speed of DDR266, or 133Mhz. Now to be pushing the FSB to 200 and above, you would need CPU:Mem dividers to keep the memory to 133mhz. At 200fsb, you would need a CPU:Mem divider of 3:2. Check to see if your desired board supports that.

If not, a single stick of Corsair XMS PC3500 will take up to about 217mhz fsb at a 1:1 ratio.

Yes, the 1:1 CPU:Memory ratio that every AMD user in the world should be using :D

EDIT:
DualDDR made simple: Dual channel. It's basically two separate memory systems working at the same time, therefore combining their total bandwidth.
 
I was thinking of picking up an nForce2 board, running the CPU at 200+ FSB, and then setting the DRAM clock to 50% of FSB. Does that sound about right?

A single stick of 256mb Corsair PC3500 costs ~$115... I can get an nForce2 mobo for ~$130 and still have 512mb of RAM. If DualDDR will really deliver the bandwidth, then that's what I'll be going for.

Imagine... you could even take PC1600 sticks and dual them and get the same bandwidth as PC3200 :eek: Cheaper for people like me who already own the PC2100 stuff and don't want to spend almost twice as much as a new motherboard for RAM.

Thanks for the replies StumpJumper. Any more comments will be welcome.
 
Last edited:
The nForce2 boards I've looked at don't run ratios like 3:2. Instead they allow you to choose a percent of the FSB the memory will run at, usually between 50 and 200. And 66% is an option for running the DDR at spec'ed speeds.

Great to know that my line of thinking isn't completely off. I think I'll be ordering myself a new mobo Monday.
 
I ran a stick of 256MB corsair pc3500 with a stick of 512MB pc3000 corsair and it worked fine. I get the full 768MB
 
That's great news for me ........... until pc3200 gets cheaper . I can thus run 768 at 166 cas2 or 185 cas 2 . Pc3000 from Corsair is known to readily reach 200 and over but normally at reduced timings . In fact cas 2 pc3000 costs more than cas2.5 3200 at Newegg .

Again I say, good news for me :)
 
eliteoneXP said:
I ran a stick of 256MB corsair pc3500 with a stick of 512MB pc3000 corsair and it worked fine. I get the full 768MB
Click to expand...

That is physically impossible. If it was infact running in dual channel, only 512mb would. What duall ddr does is split the data among two sticks, and once one is full, it can do anything to it, so that is impossible. If I am wrong, can someone explain how this wuuld work?
 
Dual Channel means there's two separate memory systems.

I think that you would get the full amount, but once one stick is full, you have to depend entirely on the other stick, therefore leaving you a little between single and dual channel speeds, since you can still at least access the full one.
 
I thought dual DDR was like Hard drives in a striped RAID array. The data to and from the CPU is put across both memory channels, and seeing as both channels feed into the one CPU, you get twice the bandwidth of the ram. Once youe smallest Ram stick of the two fills up, then that is it as far a s dual channel can go. I don't know if it kicks into single mode to access the rest of your larger stick.

And can someone with a dual channel ddr board please do a test for us:
Run your ram in dual mode, but at PC2100 speeds, and run your FSB at 166FSB. Do another test with your memory and CPU at 166FSB, and give us the numbers to see if running your memory in dual mode but at a lower FSB does/doesn't compensate for the memory's FSB being lower then the CPU's. This will answer a question a Lot of people have.
 
Dual Channel mean 2 channels accessing two separate sticks of memory at once. Think of one processor using the memory systems of 2 motherboards (kinda weird, but basically like that). You could loosely relate it to a RAID.

strokeside - listen up....

Okay, let's start off assuming you're talking about an AMD system. 166fsb is an effective 333. PC2100 runs at 133mhz, effective 266. Now when you run RAM in DualChannel, whatever the effective speed (DDR333, DDR400, whatever) is, just multiply it by 2, and you'll get the effective speed of the entire memory system. Example: PC2100 Dual Channel = 133mhz x 2 sticks = 266mhz = DDR533 (perfect match for Intel's).

Basically, running PC2100 in dual channel will make up for the memory's FSB being lower than the CPU's, at a given 166mhz. PC2100 Dual Channel is fast enough to feed Intel's 533 bus!


EDIT:
Just as a side note for everyone for the TRILLIONTH TIME!!! PLEASE don't bother attaining such high memory bandwidth figures in an Athlon system, you're wasting your time and money, because that processor/system would never know what to do with all of it.
 
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