• First the most obvious, make sure your BIOS version is current and as close as possible on revision number on every node of a cluster.  The majority of issues can be avoided by getting the bios revision as close as possible (if not identical) on all physical hosts.
• Make sure all BIOS settings are consistent across all nodes of a cluster.  Human error can get you here, even if you think all of the settings are the same, check again.
• If you are using HP Blades with on-board FC HBA’s make sure to leave them enabled or else you may not be able to install ESX as described in this article .
• Enable the "No Execute Memory Protection" in the BIOS of all nodes or vMotion and EVC may not work .
• Select "Windows 2000" as the operating system in the BIOS.  Except for the DL 740 and DL760 which should select "Linux" as recommended in this article .
• Set the "MPS Table Mode" to "Full Table APIC" as described in the previous article .
• Be cautious of interrupt sharing and balance devices across interrupts so that you do not run into performance issues like those described here .  There’s also an updated article for ESX 3.5 which describes it here .
• On AMD Opteron systems the BIOS gives an option in the memory settings for "Node Interleaving".  The workloads you will be running will dictate how this is set.  This article can help you determine the proper setting.
• Enable "Intel Virtualization Technology" if available under processor options.
• If you do not have some of the settings above, they may be for a different version of your BIOS or for different hardware.
• Lastly, if you update your BIOS for any reason, go back and check ALL settings.  Occasionally manufacturers will reset the defaults for settings and an upgreat of the BIOS will change yours.

As always, if there are updates to the ones I’ve named above or if you know of additional ones, please post in the comments section.

I thought for a moment and realized I had no idea.  So I started some research.  Here’s a couple of items I found:

• Check that your BIOS is current.  There are constant bug fixes and additions to BIOS and I’m a big fan of preventative maintenance. Once you update it, check your settings again as some updates change default settings.
• Turn on VT Extensions.  This will allow you to run 64-bit guests in ESX.
• Turn off any CPU power saving features like "Cool’N'Quiet" or "PowerNow" or you could end up with time sync issues like this article describes
  
• Another possible issue I found was if the Excute Disable Bit in the CPU settings was disabled.  This can cause vMotion to fail as described in this article here .  So you would want to enable the Execute Disable Bit.
• Processor Adjacent Sector Prefetch set to enabled as per the IBM Redbooks and Processor Hardware Prefetcher set disabled.  I was not able to find a IBM link to verify these two, I found them in a VMware communities thread here .  There’s a really good description in this thread as well.  I would disable both.
• For the memory setting, the most common recommendation I’ve read is to leave it set to HPMA.  You can read additional details and find more info about this setting in this communities thread .
• For a good explanation of BIOS settings in general and what they mean, have a look at this article: "BIOS Settings Demystified"

I’m sure that there are more settings that I could not locate.  Please feel free to comment on this article with any additional BIOS setting s0 that you are aware of on IBM hardware and please document as much as possible.

I will be posting a summary of BIOS  recommendations for HP and Dell within the next week.