Underclock AMD X2 4800/2500?

External Since: Feb 05, 2008 Posts: 1

Hi - I've done a lot of digging and can't find the answer to this...

I have an AMD X2 65nm 4800 which runs at 2500MHz.
I also have DDR2-6400 800MHz RAM.

Would the system be faster if I used the stock 12.5 multiplier while
the RAM runs at 714MHz, or is it better to drop the multiplier to 12
and let the RAM run at a full 800MHz?

I've found tests which show that the 4600 (2400MHz) outperforms the
4800. The articles don't explicitly say it, but I gather it is due to
the multiplier. I'm assuming that simply dropping the multiplier
would make th 4800 run as well as the 4600? Is it is simple as that,
or is there something I'm missing.

Anyway, my apologies for posting an "underclocking" question. I don't
like to live dangerously.

Thanks.

External Since: Jul 20, 2004 Posts: 1203

On Tue, 05 Feb 2008 16:54:50 -0800, wdoe999 wrote:

> Hi - I've done a lot of digging and can't find the answer to this...
>
> I have an AMD X2 65nm 4800 which runs at 2500MHz. I also have DDR2-6400
> 800MHz RAM.
>
> Would the system be faster if I used the stock 12.5 multiplier while the
> RAM runs at 714MHz, or is it better to drop the multiplier to 12 and let
> the RAM run at a full 800MHz?
>
The multiplier has no effect on the ram speed. The system bus does. The
normal system bus is 200MHz. And normal ram bus speed for for PC6400 DDR2
ram is 200MHz also. 800MHz is not a real bus speed. It's really a data
rate with DDR2 having a 4:1 data rate. Older DDR PC3200 also has a ram
bus speed of 200MHz, but it only has a data rate of 2:1. Some MB bioses
use the real ram bus speed while others may use the bogus speeds for
settings. Look at your dram settings to determine this.

> I've found tests which show that the 4600 (2400MHz) outperforms the
> 4800. The articles don't explicitly say it, but I gather it is due to
> the multiplier. I'm assuming that simply dropping the multiplier would
> make th 4800 run as well as the 4600? Is it is simple as that, or is
> there something I'm missing.
>
I think you've misinterpreted something. An AM2 x2 4800+ will be faster
than an AM2 X2 4600+. Perhaps you're looking at 939 v. AM2 platforms or
possibly CPU's with different L2 cache sizes or different cores.

> Anyway, my apologies for posting an "underclocking" question. I don't
> like to live dangerously.
>
That being the case, I'd suggest you leave well enough alone. If you just
have to have more speed. The basics are to lower the HT speed. Lower the
base ram speed. And then increase the system bus speed to increase the
cpu speed. All of my system have X2 3800's in them. I can increase the
system bus from 200 to 233 MHz without any problems thus bringing the cpu
speed up from 2000MHz (10x200) to 2330MHz (10x233), and with monor
adjustments could get them a lot faster. But why? The stock 2000Mhz is
plenty fast enough for my use. In fact I run cpufreq and normally the cpu
speed stays at 1000MHz, only going higher when I stress it. To get max
speed out of a system you'll find yourself screwing with voltages, better
cpu coolers, etc. If you don't know what your doing or have to time learn
by trial and error, forget it. In the end, it won't help that much.

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