DRAM Frequency

[Peter McVries]

I have a 1Ghz Duron on a PC Chips 810mlr motherboard. In the AMIBios I have
the following settings (amongst others):

CPU Ratio: 10x
CPU Frequency: 100 Mhz
DRAM Frequency:100 Mhz
CPU Core Voltage: 1.760 V

I have PC133 SDRam in my system so does the above mean that I am not making
the most of my memory?

I am unable to change the CPU Frequency (grayed out).
If I change the DRAM Freq to 133, it changes the CPU core voltage to 1.792
V. Will I be doing any harm to my hardware if I increase the DRAM Freq. to
133 MHz?

I know there's stuff on Google, but I respect the sage counsel given on this
here group :-)

[Jim]

I DL'd the manual so I could verify a few things first, here's what I see.

Your motherboard support 200 or 266 CPU FSB (effective), which translates to
100Mhz and 133MHz (actual) AMD CPU's. The memory support is likewise
200/266 (a.k.a. PC1600/PC2100). Older mobo's often require the FSB and DRAM
to run in-sync, IOW, the FS and DRAM speeds are "locked" together. If you
install PC133/PC2100 memory on such a mobo, the only way to have the memory
actually run at PC2100 is to OC (overclock) the FSB. Ideally, CPU FSB=133.
Of course, using a 133MHz (266 DDR) AMD CPU (e.g., Athlon or XP 133MHz)
would make this trivial (no OC required). But the ability to OC the FSB is
a function of many factors, including, does the mobo even ALLOW you to
change the CPU FSB to anything but the CPU specification? Or it might allow
you to choose 133 instead of 100, but nothing in between. A shame really,
since the CPU might be able to handle a small overclock, to say 112MHz, but
unless you are given access to 1MHz increments in the BIOS, you're stuck!
That's why OC'ers look for such features on their mobo's, so they can fine
tune the FSB. You sometimes need to increase the CPU voltage as well when
OC'ing to maintain stability, again, some motherboards don't permit this,
most OC'er boards DO.

So with that background, let's look at your situation...

As you've noted, your CPU FSB is greyed out, indicating that the speed is
probably auto-detected by the BIOS and automatically set/locked (clearly not
an OC'er's board!). Luckily, it appears your motherboard does allow for CPU
FSB and DRAM asynchronous operations, IOW, the CPU FSB can run @ 100MHz and
the DRAM @ 133MHz concurrently, BUT, it does so by increasing the CPU core
voltage slightly. The amount of change indicated shouldn't be a problem,
it's quite nominal. More recent motherboards provide various DRAM ratio
settings to effect this same asynchronous behavior (1/1, 3/4, 4/5, 5/6,
etc). Essentially, your mobo, in addition to 1/1 synchronous behavior, has
a built-in 3/4 divider (100 / 3 * 4 =133) for asynchronous operations, nice
to have for your purposes (not all mobos do!).

So I wouldn't worry about your setup, it appears fine. However, there is
one thing, it's been shown consistently that a SYNCHRONOUS FSB and DRAM
(1/1) runs more efficiently than ASYNCHRONOUS FSB and DRAM (3/4, 4/5, etc.),
all other things being equal. The disparity in timings leads to CPU and
DRAM wait states, that effectively diminish performance. When running
synchronously, these wait states are pretty much eliminated. So never
ASSUME that simply increasing your DRAM is BETTER if you don't do it in
conjunction w/ the FSB. It would be far better if your CPU supported FSB
133MHz. It's more than the obvious 33MHz boost I'm talking about here, the
synchronicity produces an effective improvement considerably beyond that.
So if I were YOU, I'd run some performance tests and determine imperically
whether DRAM=133 is actually an improvement (and might not be!). And I
don't mean tests that just focus on memory or CPU speed independently, but
tests that exercise the CPU and memory performance TOGETHER (i.e., their
interaction), like Winstone, Drystone, 3D Mark 2003, UT3, etc., get some
real world numbers and check it out!

HTH

Jim

"Peter McVries" <pmcv...@invalidemail.com> wrote in message
news:bbj3rd$1sp$1...@news7.svr.pol.co.uk...