KingMax PC166 RAM (shown with PC150 product)
In recent times there has been much talk about new RAM technology - first there was RAMBUS and more recently the introduction of Double Data Rate or DDR RAM. While it's true that these new technologies may offer performance benefits, the fact remains that the vast majority of current systems run plain old SDRAM.
This review is going to look at some SDRAM - but there is nothing plain or old about it. KingMax have provided us with a sample of their new PC166 RAM. As the name suggests this RAM is designed to run at very high FSB (Front Side Bus) speeds. Often when overclocking - especially with Intel based systems - increasing the FSB is the usual way you can get increased performance from your system.
When overclocking a system, there are many variables that can determine the ultimate speed that your system can be pushed to, however often one of the most limiting factors is how fast your RAM can run. First there was the PC100 and PC133 standards and then several vendors - KingMax included - introduced RAM rated at 150Mhz. We reviewed Kingmax's PC150 offerings here and here. Now KingMax have gone one step further and our current review module is rated at 166Mhz. Given that, according to their website, the PC150 modules are for "avid overclockers and performance-hungry users", these new PC166 modules are clearly aimed at those users who want to squeeze the absolute most out of their systems
Just like "PC150", there is no official JEDEC standard for '"PC166 SDRAM" - and if that is the case, how did KingMax come up with the '166' rating? If you look at the picture(s) below - comparing both KingMax PC150 and PC166 RAM - you can see that the PC166 modules are made from different chips. The chips on the PC166 RAM are rated at 5 nanoseconds, while the PC150 are rated at 6 nanoseconds and KingMax's PC133 RAM uses 7 nanosecond modules.
As I mentioned earlier, there are many factors which contribute to how far a specific system will overclock, and the speed at which the RAM is stable is but one of those factors. However, knowing that your RAM will be stable at high FSB speeds eliminates one of those otherwise unknown factors. As many overclockers know, many modules of RAM will actually prove themselves stable at speeds higher than they are rated to - especially if the CAS or other RAM timings are also adjusted. But if this RAM is rated to be stable at 166Mhz, just how fast can it go?
The biggest problem with testing RAM at such high FSB speeds is that it is hard to find a system that will be stable. When I dropped the PC166 RAM into my system - Asus A7V133, Athlon 1GHz - the system was simply not stable above about 145Mhz FSB. Because the CPU is unlocked I could lower the multiplier to compensate for the higher FSB, and I was also able to test some Corsair PC150 RAM, and I still encountered the same problems. After adjusting a wide variety of settings, it seemed there was little I could do to run this board above about 145Mhz. From comments in the OCAU forums, and from a few other people, I have heard reports that a number of other A7V133 users also encounter similar problems with higher FSB speeds.
VooDoo to the rescue! We used his Borg II as the second test machine. It normally runs stable at 160Mhz FSB, sporting a CUV4X-D with dual Pentium3 866Mhz CPUs.
The complete system consisted
of:
CUV4X-D dual Socket 370 Motherboard
2 x 866mhz CPU's
Asus GF3 8200 Deluxe
SB Live
2 x 75gb IBM GXP60 drives
2 x 30gb IBM GXP75 Drives
1 x 9gb IBM SCSI160 Drive
1 x 18gb Atlas IV SCSI drive
Intel Pro100s Network card
We booted the machine with each stick, attempting to find the highest stable speed. Stability was determined by the machine's ability to boot, run the Sandra memory test and shutdown cleanly. If it did this twice with no errors, we counted this as stable. Running 3D benchmarks is not reflective of instability because it's likely that the AGP card will cause problems at such high FSB's. We tested at both CAS2 and CAS3. (For more information about CAS2 and 3 see our Corsair review here).
 PC150 @ 166MHz @ CAS3 |
 PC166 @ 166MHz @ CAS3 |
 PC150 @ 150MHz @ CAS3 |
 PC166 @ 150MHz @ CAS2 |
At CAS2, the PC150 peaked out at 145MHz - it wouldn't boot at 150MHz @ CAS2. This is lower than Agg managed with the PC150 in his review, which I put down to differences between the testbeds or possibly the sticks. The PC166 RAM steamed on to 160MHz @ CAS2 before failing. Both sticks would run at 166MHz @ CAS3 which is the highest we could test on the CUV4X-D. You will have to choose your components carefully if you want to run your system at such high FSB's.
KingMax expect the PC166 modules to sell for around the same price or a little more than their PC150 modules. When buying new RAM, the PC166 modules are certainly worth considering, especially if you expect to be overclocking your system by increasing the FSB. The fact that the PC166 RAM modules are guaranteed to run at 166Mhz FSB and can run CAS2 at 150Mhz, and are backed by KingMax's lifetime warranty are all big bonuses.
Thanks to KingMax Australia for the review unit. If you're interested in other Kingmax products, check out our review of their PC133, PC150 and 256MB PC150 sticks. These articles also go into more depth about their TinyBGA technology and PCB numbering scheme. Thanks also to VooDoo for his help with this review!
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