Hi,
This is an interim report on how to increase your RAC without replacing your whole computer and/or spending a LOT of money.

The first question you need to answer is how many memory slots you have in your Z-400? 4 or 6. You follow different upgrade paths for each version of the Z-400. In ALL cases you need to update to the latest available BIOs from HP.

For the 4 memory slot Z-400 you can upgrade by buying a W35xx cpu chip which will allow you to speed up your Z-400 significantly. I replaced a W3565 (3.20Ghz) with a W3580 (3.44Ghz)(you can go as high as a W3590) and got a significant jump in processing speed. If you have something like a W3520 (2.66hz) or slower you can significantly improve your processing speed by going to a W3580. Why not a W3590? Because I could get a W3580 for $45.

For the 6 memory slot Z-400 its a bit more complicated if you want to increase your core count from 4 w/Hyper Threading to 6 w/HT (e.g.. 12 cores effectively).

First you need confirm that you have a "boot block date" on or after 11/10/09. You will find that date just below the Bios version information in "Bios Setup" system information.

If the answer is yes. Update your Bios to the latest one available from HP.

Then locate one of the following X56xx cpus. A X5675 6 cores w/HT @3.06Ghz (95 watt TDP), A X5680 6 cores w/HT @3.33Ghz (130 watt TDP) or a X5690 6 cores w/HT @3.46 (130 watt TDP). The X5675 will save you electricity via its lower TDP and cooler running temperature. The X5680 will cost roughly half the cost of an X5690 and only be a little slower.

I have installed a X5680 on a Z-400. If I wasn't working on upgrading to a Z-600 where I hope to install 2 X5680's it would still be in the Z-400. So I installed a W3580 in the Z-400 that I had on hand after I removed the X5680. If the Z-600 upgrade project falls though, I will re-install a X5680 in my Z-400 and comfort myself with "only" 12 cores.

Enjoy,
Tom Miller

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A proud member of the OFA (Old Farts Association).