400MHz board but 200MHz in review? Don't get it.

Something I'm not understanding, and it must be something I'm missing
in the specs, description, or the review. Or something I should know
and is assumed in the review that I know...but I don't know.

Here it is: I just ordered a new mobo, CPU, and RAM:
MB NFORCE2 EPOX|8RDA3+ :
http://www.newegg.com/app/viewProduc...123-198&depa=1

CPU AMD|2500 /333 ATHLON XP BARTON% :
http://www.newegg.com/app/viewProduc...103-378&depa=1

DDRAM 512MB ADATA|64Mx64 DDR400 :
http://www.newegg.com/app/viewProduc...211-119&depa=1

The board says it supports up to 400 MHz bus, the CPU 333.
However, this review of the mobo:
http://www.digital-daily.com/motherboard/epox-8rda3+/
All it mentions is 200MHz compatibility and support.
I don't get it.
If the CPU is 333MHz, and the mobo supports up to 400 according to its
specs, what's with this 200Mhz stuff?
What am I missing?

I suppose it's something that's PC's 101, but a little clue-by-four
over the head would be helpful. =)

Oh, by the way, any opinions on how this setup plus a 128MB Radeon
9600XT video card will run Doom3? =)
Thanks!
Liam

LRW wrote:

Something I'm not understanding, and it must be something I'm missing
in the specs, description, or the review. Or something I should know
and is assumed in the review that I know...but I don't know.

Here it is: I just ordered a new mobo, CPU, and RAM:
MB NFORCE2 EPOX|8RDA3+ :
http://www.newegg.com/app/viewProduc...123-198&depa=1

CPU AMD|2500 /333 ATHLON XP BARTON% :
http://www.newegg.com/app/viewProduc...103-378&depa=1

DDRAM 512MB ADATA|64Mx64 DDR400 :
http://www.newegg.com/app/viewProduc...211-119&depa=1

The board says it supports up to 400 MHz bus, the CPU 333.
However, this review of the mobo:
http://www.digital-daily.com/motherboard/epox-8rda3+/
All it mentions is 200MHz compatibility and support.
I don't get it.
If the CPU is 333MHz, and the mobo supports up to 400 according to its
specs, what's with this 200Mhz stuff?
What am I missing?

I suppose it's something that's PC's 101, but a little clue-by-four
over the head would be helpful. =)

Oh, by the way, any opinions on how this setup plus a 128MB Radeon
9600XT video card will run Doom3? =)
Thanks!
Liam

To increase the data rate the AMD XP line operates 'double data rate',
which is a technique for transferring data on both the leading and trailing
edge of the clock vs the simpler 'one edge' technique used on earlier
systems (like the P3, AMD K6, Pentium classic, etc.).

On older systems, then, the data rate was equal to the clock frequency.
With DDR (double data rate), though, the data gets sent at twice the clock
frequency.

Cut to the chase: When the clock is 200 MHz then the data rate is twice
that for 400Mhz.

Naturally, when you look at 'ratings' they're going to show you the data
rate so your processor says "333" because it operates on a 166 MHz clocked
DDR bus that, as a result of being DDR, transfers data at 333Mhz.

When looking at clock vs data rate (in DDR systems):

Clock Data Rate
100 200 (e.g. Duron)
133.3 266
166.6 333
200 400

Here it is: I just ordered a new mobo, CPU, and RAM:
MB NFORCE2 EPOX|8RDA3+ :
CPU AMD|2500 /333 ATHLON XP BARTON% :
DDRAM 512MB ADATA|64Mx64 DDR400 :

The board says it supports up to 400 MHz bus, the CPU 333.
However, this review of the mobo:
All it mentions is 200MHz compatibility and support.

The answer toyour question is "DDR" - double data rate.

The actual (real) clock frequency will be (say) 166Mhz.
But every clock-cycle data is clocked thru mot once but twice -
once on the rising edge, and once on the falling edge.

This effectively doubles the throughput.

So, for 166Mhz on your bus, you get 333 MHz DDR.
For 200Mhz bus, you get 400Mhz DDR.

BTW: on nForce motherboards, the performance will be greatest when
the CPU bus and memory bus will be IN SYNC. This means, either (1)
overclocking your CPU bus, or (2) underclocking your memory bus,
if you want to achieve this.

Now, nowadays Athlon XP's are 'locked' - meaning they have a fixed
multiplier. Meaning, if you only change (increase) your CPU bus from
166 to 200 Mhz, you'll end up with 3000+ performance. This may be more
than the CPU can take (although, by all reports the 2500+ should be
able to reach this).

Luckily, you have an nForce motherboard. On some/most nForce
motherboards you CAN change the multpiplier even on 'locked' processors.

So, to stay safe and not overclock your CPU, you could increase the bus
and then lower the multiplier so you end up with the same end result.

See:

http://www.viperlair.com/articles/ho...ck/index.shtml

for an explanation of what I'm talking about.


Oh, by the way, any opinions on how this setup plus a 128MB Radeon
9600XT video card will run Doom3? =)

It should run fine.

But i would go for the 9800 Pro 128MB, if getting a new videocard.
There's only $30 difference in price.

David Maynard wrote in message ...
LRW wrote:
If the CPU is 333MHz, and the mobo supports up to 400 according to its
specs, what's with this 200Mhz stuff?
What am I missing?



Cut to the chase: When the clock is 200 MHz then the data rate is twice
that for 400Mhz.


Oh, OK. Thanks. =)

Liam