Crucial's DDR PC2700 DRAM Module
166MHz DDR DRAM on
board 333MHz effective bandwidth
Below, we've taken a couple
of pictures of the new "official" PC2700 DDR DRAM modules
from Crucial and below that, "PC2400" modules from Corsair
Micro. Now, although Corsair is a well known high
quality memory module manufacturer, they are taking small
liberties, so to speak, with respect to the naming of their
product, due to the fact that the JEDEC board never
standardized a "PC2400" specification for DDR DRAM modules.
PC2700 333MHz DDR CAS 2.5 Memory Module
DDR PC2700 ? CL=2.5 ? Unbuffered ?
Non-parity ? 6ns ? 2.5V ? 32Meg x 64
"PC2400" 300MHz DDR CAS 2 Memory Module
DDR PC2100 ? CL=2 ? Unbuffered ?
Non-parity ? 7.5ns ? 2.5V ? 32Meg x 64
could draw the conclusion that since the screened 300MHz
Corsair modules effectively yield 2.4GB/sec of bandwidth at
their rated speed, that you could call them "PC2400"
product. However, that is more of a marketing play
than anything else frankly. Regardless, what is
important to note is the basic spec with any DDR module.
The Corsair modules have 7.5ns rated Micron DRAMs on them or
133MHz SDR (266MHz DDR), so if you are running them at
300MHz, you are effectively overclocking the product but
then again, Corsair already screened them to ensure
stability at that speed.
Crucial official PC2700 modules, shown above, have 6ns.
rated Micron memory on them or 167MHz SDR (333MHz. DDR).
As you will note, these modules are therefore built with
memory that was designed to run at 333MHz DDR and are
designed to meet the exacting JEDEC PC2700 specification.
It has been only with this recent release of, "officially"
built PC2700 memory, that the SiS645 chipset has been able
to run its DRAM memory subsystem, at the speeds it was
architected for and within component specifications.
aggressive and "within spec" memory timings brought forth to
the SiS645 chipset, we should see more impressive
performance for all motherboards based on this platform,
especially when compared to its RDRAM based rival, the i850.
Installation / Setup
SiS finally gets the
memory it needs
Abit's SD7-533 BIOS Setup
Setup and Voltage
Strange FSB Divisors
Advanced Chipset Features
There are some
interesting and frankly, totally confusing, features in the
BIOS setup of the SD7-533. For starters, this board
has a multitude of AGP/PCI Divisor options, that can let you
run system memory and CPU Front Side Bus at various speeds,
while adjusting the speeds of the AGP and PCI bus. The
problem is that you need a scientific calculator to figure
out what on earth each setting will yield. OK, perhaps
that is a little harsh on the BIOS Programmers at Abit.
However, it took us far too much effort in trial and error
work, to get the desired 166MHz (333MHz DDR) Memory Bus
speed set up with an acceptable AGP and PCI bus speed.
At first we were running into problems with the AGP bus
being run way out of spec at 80MHz, when the memory was set
to 166MHz. We were being met with lock-ups and crashes
during some of our testing as a result. However, we
were able to finally plug in a setting at a 166MHz memory
clock, that allowed us to run the AGP bus within spec.
Abit certainly could have made it much easier on the end
user, if they went with a significantly more simplistic
approach to their Divisor nomenclature in the BIOS of this
One other small
hurdle, at least at this point in time, is that the BIOS on
this board only allows up to a 1.625 voltage setting on
Northwood CPUs, which may limit your overclocking endeavors.
However, we are hopeful that Abit will hear the call of the
power user crowd and release a new version of the BIOS that
yields voltages up to the 1.85V setting. Finally, as
you will note in our screenshot of the DRAM timing setup, we
were able to run our Crucial DDR PC2700 DRAM at a speed of
333MHz DDR and a CAS 2.5-2-2-2 setting in "Turbo Mode".
Now, that should kick things up a notch for sure. We
didn't try a full CAS2 setting, because it was out of spec
for the module. However, we have sneaking suspicion
that it could handle it just the same.
Overclocking and preliminary Sandra and PCMark tests