Undervolting Athlon64 3500+

Here's a quick question about undervolting Athlon 3500+ (Newcastle core).
I undervolted my zv6000 and frankly, I was amazed when the cpu worked at 5x with 0.850v (1 ghz). The only problem I encountered was that I could not set the Athlon to work at 800mhz, that is 4x, no matter what voltage I set. As soon as I create a 4x P-transition state, the notebook freezes. I also noticed that if RMClock is disabled and I let Windows manage the throttle, the CPU would again only go to 1ghz and not 800mhz.
I thought this was the way Athlon 64 works and forgot about it. Yet, today I visited RMclocks' site and found this
( here's the link: http://cpu.rightmark.org/products/rmclock.shtml)

The Athlon64 on the screenshot is working at 4x, 800mhz. Can anyone tell me why I cannot set my zv6000 this way? Is there a fundamental difference between the Clawhammer and the Newcastle cores ? Or could it be that I was using RMclock 1.8 there?
Thanks

 

May be new castle core does not go below 5x. My friends Athlon64 did not go below 5x either.

 

If you check the datasheet for the Newcastle A64 3500+, the minimum P-state is 1000Mhz (5x). Other revisions can go to 800Mhz (4x).

 

Oo, my desktop has a clawhammer Athlon 64 3200+

 

The S939 newcastle can only go upto a minimum multiplier of 5x. It is a given fact that HP uses a desktop processor and there is no need to go down all the way to 800MHz since it does not yield that much of an improvement in a desktop environment.

 

Thank you guys, it's good to know there's nothing wrong.