DDR550 and 2000mhz fsb

[CMH]

As some of you may know, I'm building a pc, and I'm getting more and more confused about this ram and fsb.

yes, I know the DDR550 is not for the sane, but at least the 2ghz fsb is.

now, assuming I can fork out the money for the DDR550, can the 2ghz fsb support it? I'm not too much into overclocking, but I kinda know (or at least I think I do) that ddr400 ram running at dual channel is the max an 800fsb bus can take. Correct me if I'm wrong.

Now, apparently there are 2000mhz fsb around, and apparently I'd be underutilizing this if I get the ddr400. Therefore I looked into the realm of the ddr550 to reduce this bottleneck.

 

[zephead]

can you be more specific as to what platform you're referring to?

 

[CMH]

I didn't know it'll matter, I'm just wondering what the speeds are like, just want to push the FSH to full potential (given that in my understanding, thats usually a bottleneck in high end systems).

Anyway, thinking of an AMD system, maybe a 3500+ socket 939. With 1gb of RAM, uber graphics (non SLI), yada yada yada....

 

[zephead]

you'd see that 2000 mhz fsb emerging these days, what with the dual core and all.

 

[CMH]

Yeh, but 2000mhz fsb is not gonna be taken advantage of as far as I know.... RAM speeds aren't up there yet... not even close. Unless they have Quad Channel RAM.....

 

[zephead]

because of amd's on chip memory controllers, the performance gains will be very real.

 

[vnf4ultra]

Ok, amd 939 processors have a 2000MT/s bus, which is 1000mhz. Ok these cpus have a 200mhz "htt speed", which is multiplied by a "htt multi" to get the htt bus speed, which is 200 x5 normally, which gives you 1000. You don't want the htt over 1000, so you have to lower the htt multi to 4, or 3 depending on the oc to keep it stable. You get the cpu speed from the htt speed X the cpu multi(built into chip), so a 3000+ is 9(multi) x 200 = 1800mhz. The mem is the htt speed, multiplied by two (because of ddr), so at stock, it's 200mhz x 2 = 400mhz, or ddr400(pc3200). To use ddr 550, you'd need to oc to 275 htt, which would put your cpu at 2.475 ghz if it's a 3000+. Hope this helps.
High speed ram is only needed for high oc's.

 

[CMH]

That helps alot.

So if I'm not interested in OC, what speed RAM would already fully utilize whats available?

 

[vnf4ultra]

For an amd 939 system, the default htt speed is 200mhz, which corresponds to pc3200 (ddr400) ram. DDr basically doubles the data rate, so the 200 clock is effectively doubled to 400(as in ddr400). Some newer intel systems use ddr 2 of 533mhz and up, but I don't know if that helps performance much or not.

 

[CMH]

I can say right now: apparently not much, due to the higher latency.

But then again, its like a stepping stone, first gen products will show little improvement, but its vital to get to the next gen, and hopefully by then they've improved on it till its really worth it....