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Compatability and Identification
Unfortunately, KingMax do not have the best reputation among the overclocking and enthusiast community. A lot of people, possibly the majority, have no problem at all - but there have been a few well-publicised times when a really bizarre instability problem was solved by switching away from KingMax RAM. I first experienced this myself with my Soyo SY-6VBA-133, a year ago now, when I spent a weekend trying to make the board run stably at 133MHz FSB. I finally tracked the problem down to ALL THREE of my 64MB KingMax PC133 sticks. The Soyo worked fine with every other stick I put into it, but any of the KingMax's and it would refuse to power up, hang during the boot or spontaneously reboot even under mild load. JimX noted a similar problem during his MSI BXMaster review.

I noticed the same thing during my recent Abit KA7 review. This time I had a 128MB stick and a 64MB stick here, and they both had the same problems. There really seemed to be some kind of issue with using KingMax PC133 on certain motherboards, mostly those based on VIA chipsets. I have confirmed this with other people via email and in IRC, but can find no mention of this problem on KingMax's website. After explaining the problem to Alex Tse, KingMax Australia's Assistant Director, he seemed unaware of this issue but was eager for me to do some testing to confirm the problem and to see if the v1.2 sticks have the same problem. He also assured me that, if you were experiencing a problem with a pre-v1.2 stick, it would be covered under KingMax's lifetime warranty, so you could exchange it for a v1.2 stick.

What's all this v1.2 business? Well, consider a stick of RAM as 2 parts - the chips themselves, and the PCB (printed circuit board) they rest on. The PCB does more than just carry the signal from the chips to the RAM slots on your motherboard. There may be buffering, error-correcting, identification or other logic, depending on the particular type of stick. KingMax have revised this particular PCB design at least twice. Let's see how to identify what revision your sticks are. It's pretty easy to find, written on the end of each stick like so:

PC150 uses the v1.2 PCB	..as does the new PC133 stuff.
v1.1 is labelled on the other end..	..while v1.0 isn't labelled at all.

This big picture below shows that the layout is actually quite different between versions. Click the picture for a BIG closeup (163KB) that shows it in more detail.

click for (much) bigger pic
from top to bottom:
v1.0 PC133 (64MB)
v1.1 PC133 (128MB)
v1.2 PC133 (128MB)
PC150 (128MB)

So, does the v1.2 revision make any difference? I experimented with the 64MB v1.0 stick and the 128MB v1.1 stick for a couple of hours in my KA7 and SY-6VBA-133 again. Both immediately demonstrated the same problems I described above - even with the latest BIOS in the KA7, which apparently has "greater SDRAM stability". However, putting the PC133 v1.2 stick or the PC150 into the KA7 immediately returned it to rock-stable, allowing me to run the benchmarks you'll see on the next page. The Soyo has now been running with BOTH these v1.2 sticks at 133MHz, CAS2 (this is above their rated speed) with no problems for a couple of weeks - and this is my main workstation, the machine I am typing this article on now. It definitely seems that KingMax have gotten it right with their v1.2 PCB - I've had no stability problems with either stick at all. Great stuff!

Now, let's see how it performs under duress..