Abit's SD7533 SiS645 P4 Motherboard and Crucial DDR

Abit's SD7533 SiS645 P4 Motherboard and Crucial DDR PC2700 DRAM - Page 2


The Abit SD7-533 Motherboard With Crucial DDR PC2700 Memory
A SiS645 Pentium 4 board with Abit flare - DDR PC2700 Done Right With Crucial

By, Dave Altavilla
April 23, 2002

Crucial's DDR PC2700 DRAM Module
166MHz DDR DRAM on board 333MHz effective bandwidth

The Difference:

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. 

Crucial DDR PC2700 333MHz DDR CAS 2.5 Memory Module

DDR PC2700 ? CL=2.5 ? Unbuffered ? Non-parity ? 6ns ? 2.5V ? 32Meg x 64 


Corsair "PC2400" 300MHz DDR CAS 2 Memory Module

DDR PC2100 ? CL=2 ? Unbuffered ? Non-parity ? 7.5ns ? 2.5V ? 32Meg x 64 

However, one 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.

However, the 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.

With more 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 Of The Abit SD7-533
SiS finally gets the memory it needs

Abit's SD7-533 BIOS Setup

CPU Setup and Voltage

FSB Divisors

Strange FSB Divisors


Integ. Periphs

Health Monitor

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 board.

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

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