Zalman CNPS9500 AT LGA775 HSF - Cooler Performance and Conclusion

Article Index
Zalman CNPS9500 AT LGA775 HSF
Test Setup and Installation
Cooler Performance and Conclusion

Testing Methodology:

When testing CPU coolers we install the cooler at least twice to ensure that the cooler is installed properly.  We use Arctic Silver Ceramique on all units to level the playing field.  We also test the coolers with the case sides on to replicate "real world" scenarios.  While it's true that a lot of tweakers leave the side off their case, we are assuming that most people will have their case closed.

To heat things up we ran an instance of the Folding @ Home client on each CPU core and set it to "slightly higher than idle" CPU usage.  We also run Prime95 to really make things toasty.  When running these programs CPU load is pinned at 100% and it's gets warm in a hurry.  Load temps with the fan at low and high are recorded 45 minutes after the tests are initialized.  For idle temps, we boot up and let the machine sit for 15 minutes to get things warmed up.  CPU load at idle is generally between 1%-2%.

Take a look below as we turn up the heat on this heatsink as we take our Intel 805 CPU up past 965 speeds and see if the Zalman CNPS9500 AT can cool off 7.8GHz of Pentium D goodness.

Performance Tests:

In this our first LGA775 HSF review we have only the stock Intel HSF to compare with.  Obviously the Zalman CNPS9500 AT will outperform it, but by how much?  Will better cooling enable the processor to overclock higher?  Let's have a look.

Stock speed of this processor is 133x20 = 2.66GHz.  It runs with a quad-pumped FSB which is effectively 533FSB.  Other Dual Core Intel processors run at 800FSB (200 quad-pumped), so this processor has a disadvantage in the bandwidth department, but due to it's low FSB, has an advantage in the overclocking department.  Stock voltage is 1.375v and we never ran it above 1.525v when overclocking.  To stress the coolers to the max, we overclocked the CPU as high as we could and remain stable.  Stability was determined by running Prime95 and Folding @ Home.  If the system could remains stable overnight, we considered it stable.  Our maximum stable speed with the stock cooler was 3.66GHz (180x20) at 1.525v, and with the Zalman CNPS9500 AT we achieved 3.9GHz (195x20) at the same 1.525v.  I'm sure I could break 4GHz with this processor, but because I had to purchase it with my own money, I don't really want to hose it.

We ran tests with the fans set to "Auto" and "High".  Auto fan speed scales with the heat output of the CPU and varies greatly in rpm.  It is impossible to recreate the same RPM on each cooler at different degrees, but we included the numbers anyway.  If you are not an enthusiast and you wonder how these coolers compare without tweaking or adjusting fan speed, the "Auto" numbers will be your friend.  If you don't care if a HSF makes a little noise, take a look at the numbers when running the fan at 100% - "High" speed.

Stock Temps
Stock Temps

At high speed both the stock cooler and the Zalman CNPS9500 AT make a fair bit of noise.  The Zalman cooler bests the stock cooler by a chilly 10 C though.  That's a pretty big margin for sure.  When running auto fan speed the margin is narrowed to 8 C.  Keep in mind because the Zalman HSF is keeping the processor cooler, the fan is also running slower.  At idle both coolers do a fine job, but the AT keeps things about 6 C cooler.  Not bad for a dual core Pentium D.  Let's take a look below at the overclocked results.


This time around we take the CPU and push it until it's on the bleeding edge of stable - then we back it off until it is stable.  With the stock cooler we managed to push this 2.66GHz CPU up a whole GHz to 3.66GHz.  At this speed things got a little warm for sure.  With the Zalman cooler installed we were able to squeeze another 240MHz out of this processor without bumping up the voltage.  That puts us in the 3.9GHz range and brings us to an incredible 46% overclock.  I believe that if we tried a little harder we could have made 4GHz and a 50% overclock, but I didn't want to fry this CPU just yet.

Max Overclocked Temps
Max Overclocked Temps

As you look at the chart above and see the margins narrow up even more than at stock speeds, you must keep in mind that the Intel 805 processor is clocked higher under the Zalman cooler.  After a certain point every little MHz bump increases the heat output exponentially, and with the stock cooler I couldn't get to 3.7GHz stable, let alone 3.9GHz.  Even when cooling 7.8GHz of processor, the Zalman CNPS9500 AT keeps things just under 60 C in out 20 C ambient test area.  It's a rise of 39 C above ambient, but that's not bad consider what it is trying to cool.


After a bit of a blunder and requesting a HSF that I didn't have a test rig for, I actually had a good time playing around with an Intel rig again.  The last Intel rig I owned was a Celeron 300A and it too was a great overclocker.  The Zalman CNPS9500AT seems to be a perfect fit for Intel's 805 processor and allows you to keep things cool enough to squeeze out a bunch of extra performance.  If you're looking for a good cooler to keep your toasty LGA775 gear cool, you must check out the 9500 AT for yourself.  You won't be disappointed.


  • Medium Weight Cooler.
  • Great Performance.
  • Quiet at stock speeds when not overclocking.
  • Nifty design with 3 "Figure 8" heatpipes.


  • Finish of base a little rough.
  • No Fan Controller.
  • LGA775 only.

This is a nice cut-down package from the CNPS9500 LED cooler.  It is built only for Intel 775, but it should be able to found cheaper than the previous Zalman cooler with all of the bells and whistles.  It has a unique design that has proven to be very, very good. Rating
Software Pack:
Total Score 9.0


I'd like to thank Zalman USA for letting us take a look at this unit.  It's been an interesting ride as we get back into some Intel gear.

If you have any questions or comments regarding this review, please head on over and post them in our forum at the "Comments" link below.  Thanks a bunch!!