533mhz dddr

[Emlyn]

I'm a novice with this stuff, so forgive me if it seems very
basic...I've seen on some sites, mention that "dddr" memory is what's
used to break the 400mhz barrier. However, I notice that motherboards
(and associated dddr memory) for the AMD socket 939 chip only go as
far as 400mhz. How come the pentium boards take 533mhz memory, but
not AMD? Are there plans to take AMD to 533mhz any time soon?

Anywhere I could read up on this?

Thanks.

 

[Louis V. Nguyen]

Pentium 4 CPUs starting with the Intel 845D chipsets use Dual Channel Memory
Controllers. The CPUs themselves are Quad Pumped Front Side Bus. So when you
see 533MHz, it really is talking about DDR266 PC2100 Ram in Dual Channel to
equal the CPU FSB of 533MHz. Does that clarify it for you?

 

[Wes Newell]

I'm a novice with this stuff, so forgive me if it seems very
basic...I've seen on some sites, mention that "dddr" memory is what's
used to break the 400mhz barrier. However, I notice that motherboards
(and associated dddr memory) for the AMD socket 939 chip only go as
far as 400mhz. How come the pentium boards take 533mhz memory, but
not AMD? Are there plans to take AMD to 533mhz any time soon?

Anywhere I could read up on this?

First you need to understand the marketing BS. None of these boards, Intel
or AMD run memory at anywhere close to 400MHz. DDR ram does not run at
533MHz. PC2100 ram runs at 133MHz DDR, (DDR meaning Double Data Rate)
and data rates aren't measured in MHz, but Bps (Bytes per second) or bps
(bits per second). At the higher end of the ram PC3200 is rated for 200MHz
DDR and PC4400 is rated for 275MHZ DDR. Once you understand this it might
help. AMD's memory controller is rated for a true 400MHz now which is
faster than any DDR ram currently made (PC4400 is only 275MHz), so the
limitation you are speaking of isn't there. I've seen reports that the
default FSB of the new EE P4 is 266MHz but I don't know this for sure. Any
any case it doesn't matter. Next, I think you are getting the FSB (Front
Side Bus) and the memory bus mixed up. These are not the same buses. The
memory bus is seperate from the FSB and can run at different speeds. The
only correlation between the FSB and the ram bus is that the ram bus speed
usually follows the overclock of the FSB when overclocking the FSB, so
setting the base ram bus to 200MHz and the FSB to 266MHz would result in a
ram bus of 266MHz also. But for this to work you will need PC4200 (266MHz)
capable ram. Since most people not knowing all this usually buy PC3200 ram
they would need to lower the base ram bus speed to 133MHz to keep the ram
bus within the limits of the ram. 133MHz base + 66MHz oveclock would set
the actaul ram bus speed to 200Mhz with a FSB of 266MHz. I don't know if
this helps or not, but that's it.

 

[dawg]

Isn't the latest Intel Chipset running a 1066 bus with 533 DDR-2?

 

[Ed]

Isn't the latest Intel Chipset running a 1066 bus with 533 DDR-2?

I think it's only for the P4 EE CPUs, the faster bus and DDR-2 still
can't beat a cheaper built AMD-FX.
http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=2261

Ed

 

[Wes Newell]

Isn't the latest Intel Chipset running a 1066 bus with 533 DDR-2?

i would ask which bus, but it doesn't matter, the answer is no if you mean
MHz. I think the new P4 3.73GHz EE runs with a 266MHz QDR FSB. That would
make the FSB lines 1066Mbps. They could also run the ram bus at 266MHz,
but so can AMD. And since the AMD has much lower latancy than the Intel
chipset and the ram data doesn't have to go over the FSB, the AMD bus is
faster and thus has more bandwidth. Speaking of a 939pin A64/FX cpu of
course.

 

[Emlyn]

First you need to understand the marketing BS. None of these boards, Intel
or AMD run memory at anywhere close to 400MHz. DDR ram does not run at
533MHz. PC2100 ram runs at 133MHz DDR, (DDR meaning Double Data Rate)
and data rates aren't measured in MHz, but Bps (Bytes per second) or bps
(bits per second). At the higher end of the ram PC3200 is rated for 200MHz
DDR and PC4400 is rated for 275MHZ DDR. Once you understand this it might
help. AMD's memory controller is rated for a true 400MHz now which is
faster than any DDR ram currently made (PC4400 is only 275MHz), so the
limitation you are speaking of isn't there. I've seen reports that the
default FSB of the new EE P4 is 266MHz but I don't know this for sure. Any
any case it doesn't matter. Next, I think you are getting the FSB (Front
Side Bus) and the memory bus mixed up. These are not the same buses. The
memory bus is seperate from the FSB and can run at different speeds. The
only correlation between the FSB and the ram bus is that the ram bus speed
usually follows the overclock of the FSB when overclocking the FSB, so
setting the base ram bus to 200MHz and the FSB to 266MHz would result in a
ram bus of 266MHz also. But for this to work you will need PC4200 (266MHz)
capable ram. Since most people not knowing all this usually buy PC3200 ram
they would need to lower the base ram bus speed to 133MHz to keep the ram
bus within the limits of the ram. 133MHz base + 66MHz oveclock would set
the actaul ram bus speed to 200Mhz with a FSB of 266MHz. I don't know if
this helps or not, but that's it.

Thanks. So, even if I buy a socket 939 mobo and it says it handles
dual channel ddr, what's the current upper limits of what they can
handle? Could you put in dual pc4400?

Thanks.

 

[Wes Newell]

Thanks. So, even if I buy a socket 939 mobo and it says it handles
dual channel ddr, what's the current upper limits of what they can
handle? Could you put in dual pc4400?

Yes, you can use PC4400. That would make the upper limit for the ram bus
around 275MHz DDR550. The highest you can set the ram bus speed to is
probably 200MHz, but anything you add to the FSB will also be added to the
ram bus, so if you set the fsb to 266 then the ram bus wil also run
266MHz. If you set it to more than 275MHz, then you will need to lower the
Base ram bus speed to 166MHz or even lower to keep the ram within its
rated specs. IIRC, the lowest I can set the ram to on my board is 133MHz,
so using PC3200 ram, the highesy I could set the FSB to and still keep the
ram within specs is 266MHz. For me, that would be enough, but if you had a
cpu with only a 9 multiplier that would only be about 2400MHz. You would
also loose a little performance with the ram bus at 200Mhz compared to
266Mhz if you ran it in sync.

 

[Emlyn]

Yes, you can use PC4400. That would make the upper limit for the ram bus
around 275MHz DDR550. The highest you can set the ram bus speed to is

How do you "set" the ram bus speed? In the BIOS?

probably 200MHz, but anything you add to the FSB will also be added to the
ram bus, so if you set the fsb to 266 then the ram bus wil also run
266MHz. If you set it to more than 275MHz, then you will need to lower the
Base ram bus speed to 166MHz or even lower to keep the ram within its

If you increase the fsb to more than 275Mhz, why would you *lower* the
base ram bus speed? Also, is the ram bus speed the same as the "Base"
ram bus speed?

rated specs. IIRC, the lowest I can set the ram to on my board is 133MHz,
so using PC3200 ram, the highesy I could set the FSB to and still keep the
ram within specs is 266MHz. For me, that would be enough, but if you had a
cpu with only a 9 multiplier that would only be about 2400MHz. You would
also loose a little performance with the ram bus at 200Mhz compared to
266Mhz if you ran it in sync.

Do you know any good sites for explaining all this? A "RAM / FSB for
dummies" if you like

Thanks again.

 

[Wes Newell]

How do you "set" the ram bus speed? In the BIOS?

Usually, although it could be via jumpers, and a really cheap board my not
even have settings for it and have it fixed.

If you increase the fsb to more than 275Mhz, why would you *lower* the
base ram bus speed? Also, is the ram bus speed the same as the "Base"
ram bus speed?

If your ram is rated for 275MHz (PC4400) and you have it set for 200MHz,
then set the FSB to 300 MHz, the ram bus will also be 300MHz.

Do you know any good sites for explaining all this? A "RAM / FSB for
dummies" if you like

And I thought I did a good job of it. Try a search engine. I don't
know.