Testing
For testing I used Gigabyte's SINXP1394 motherboard, which is based on the SiS655 chipset that has been making waves in the Pentium 4 DDR community. I've now been testing this SiS655 board for two weeks, and after comparing results with other users, we have concluded that this chipset is VERY harsh towards memory, it's memory controller is faster than any other DDR based P4 chipset available, so if you believe that the timings this RAM was tested at were comparatively slow, give your usual timings a whirl on the SiS655 and watch as the motherboard refuses to POST! However, unless otherwise stated the CAS was at 2. All voltages were left at default throughout the testing.
Other components in the system were a Pentium 4 2.4B GHz, for the most part kept at default clock speed; an ATi Radeon 9700Pro, running at default clock speeds, using Catalyst 3.2 drivers; a Barracuda ATA V 120Gb Hard Drive, with Windows XP Professional SP1 loaded and SiS AGP 1.15 driver.
First up, Sisoftware Sandra 2003 SP1 (Version 9.44)
SiS655 has a huge range of memory ratios, meaning that even at 133MHz Front Side Bus, we can run the RAM at DDR446 (223MHz). By the looks of things, SiS655 works best with Dual DDR333, as it produces 3.3Gb/s bandwidth at this setting. However, it would seem that Gigabyte's latest BIOS for this motherboard is playing havock with the stock DDR400 settings, as while this Sandra memory benchmark is lower for DDR400, there is still an increase in performance elsewhere as you'll see later. Note the maximum speed achieved on the SiS655 was DDR470! For this we had to raise the CAS to 2.5, and as the Front Side Bus is not as high as the last result on the graph, the bandwidth is lower.
This next Sandra test shows unbuffered bandwidth, which is what Sandra used to benchmark up until around 2 years ago. Some say that unbuffered bandwidth gives a better example of what real world performance will be like, and certainly the results are very interesting. At DDR446 on the stock 133MHz FSB, the raw throughput is quite amazing, at over 2.2Gb/s. Notice again that we are able to run the the EL-DDR at CAS 2, even at DDR446, which is exceptional in a Dual Channel SiS655 system such as this, and all this on default voltage.
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