Ram confusion: MHz vs PC* ****

Do you have a question? Post it now! No Registration Necessary.  Now with pictures!

Threaded View
Husband and I might have to put together and SLI system for him to game
We are thinking og getting this mobo:
It's memory specs:
DDR2 667
TigerDirect says:
" The nForce 570 SLIT-A provides 4 DIMM sockets using Dual Channel 240-
pin DDR2 with a total capacity of up to 4GB. You can install DDR
533/667MHz Memory."
NewEgg and ECS say the board will take 16 GB of ram.
At New Egg I can choose RAM  from
DDR 2 667 (PC2 5300) OR
DDR 2 677 (PC2 5400)
Which do I pick and how do these numbers relate to MHz?
Looking here:
I see most of the SLI certified memory is 800MHz or better.
This board will only use 667MHz, correct ? To buy 800MHz ram would be a
waste of $?
Was thinking on getting 4 sticks of this:
How do I tell the MHz of this ram? Is it the right type? Am I over
What the heck does PCX XXXX refer to anyway?
Why doesn't Newegg list MHz?
CPU specs if needed:
Name     Core 2 Duo E6700
Operating Frequency     2.66GHz
FSB     1066MHz
L1 Cache     32KB+32KB
L2 Cache     4M sharing

The solution is:
Winrar and/or DvdDecrypter.
Install the ac3 audio codec.

Re: Ram confusion: MHz vs PC* ****

Machine Messiah wrote:
Quoted text here. Click to load it

What counts, is whether you have sufficient specifications in order
to select a product. Selecting a product is what Newegg is interested

The two numbers are million transfers per second:  DDR2-667
and megabytes per second:                          PC2 5400

A DIMM is a 64 bit wide creature. That is 8 bytes of data. If the
module transfers 667 million items per second, and each item is
8 bytes wide, then that is where the (rounded up) marketing number
5400MB/sec comes from (667 * 8). This Wikipedia article tries to explain
that there are other numbers, but those are unimportant to the selection
process. (I.e. External clock signal 333MHz. Internal 4N fetch of data
from the memory array at 166MHz. Double data rate data bus output at
667MT/sec, or DDR2-667. The memory array prefetches 4 bits at 166MHz,
and the four times faster memory bus eats them at 667Mhz, so
it balances. That is as near as I've been able to figure it out, since
I haven't found an article that shows both internal and external


The DDR2-667 is enough detail to make a selection, without bothering
about how the rest of it works.

(These are highly technical documents, and I offer these because I
cannot find a good tutorial instead. The second document is a datasheet
for a DDR2-800 memory chip. The first document is a comparison article,
comparing SDRAM, DDR, and DDR2.)


Memory is backward compatible speedwise, and that means a DDR2-800
stick can be used in a DDR2-667 or DDR2-533 application. Since the
maximum clock period in the chip datasheet above lists 8ns, that is
a 125MHz clock or DDR2-250, meaning the fastest memory chips can
be slowed down to slower than the lowest JEDEC spec'ed speed (DDR2-400).

The problem is the BIOS. If a DDR2-667/533 motherboard is presented
with a DDR2-800 DIMM, it is all up to the BIOS, whether it does the
right thing (automatically selects the right clock values). There
have been (and will continue to be for a while) nasty BIOS that don't
work well. If you have a slow stick handy, you could try manually
setting up memory clock rate with a slow stick, power down, and
install the good stuff. You may be able to trick the BIOS that
way - at least that approach worked with DDR having similar

Nvidia chipset comparisons are here. 570 is a PCIE 8/8 SLI chipset.

This is a manual for another product that uses Nvidia 570. The
memory seems to have the capability to run async, if a clockgen
chip is available to do it.


And here is an article reviewing 570SLI operation. Core2 runs
FSB1066 (266MHz clock quad pumped), DDR2-533 is 1:1 divider,
and DDR2-800 is reached with a 2:3 divider (3/2 * 266*2).
It would seem the chipset is capable of many things, and
the feature set will depend on the company making the motherboard,
the target market and price range. Notice in the tables
here, how little difference the DDR2-800 memory speed is
making (Winrar tends to exaggerate the importance of memory
bandwidth, and shows 11 second improvement on a 332 second execution
time program or around 3%).


What I don't understand in your build, is the wish to go
for 4*1GB config. 2*1GB should be more than sufficient for
Vista, Photoshop, video editing etc. What will 4GB be
used for, and what OS will really take advantage of it ?
I recollect that applications in the Windows environment
have limitations on how much memory thay can access, and
my worry would be you won't get the value from the RAM
on too many occasions. The ECS motherboard tells me you
want to economize a bit, so why 4GB ?


Re: Ram confusion: MHz vs PC* ****

Quoted text here. Click to load it

you could try these guys
probably  a handful who will know

or some very rare character in an OC ng may know

Re: Ram confusion: MHz vs PC* ****

Quoted text here. Click to load it
Thanks for the in-depth reply. The wikipedia article was helpful.
My husband wants to start with at least 4 gigs of ram, he's going to
game on this machine. The only "economizing" he's doing is not buying a
Core 2 duo "Extreme" processor just. Asking him to game with a mere 2
gigs of ram would be like asking him to game online w/a Celeron. I have
2 gigs of ram on MY machine.
He wants a Core 2 duo CPU and an SLI mobo. The only problem I see with
this 570 chipset is the SLI is X 8. The older nForce 4 boards can do SLI
X 16.

The solution is:
Winrar and/or DvdDecrypter.
Install the ac3 audio codec.

Re: Ram confusion: MHz vs PC* ****

The current edition of Maximum PC discusses this issue.
I THINK their conclusion was if you can afford it get it, but it is
not "all-that".  They also discuss "High Speed" v/s low latency.  You
can have one OR the other.
(As soon as I find the mag I'll give you some more info.

On Mon, 2 Oct 2006 22:37:55 -0400, Machine Messiah

Quoted text here. Click to load it

Site Timeline