Does Xeon westmere ep (xeon 56xx series) have vt-d (=iommy / direct io) or does intel TXT (Intel® Trusted Execution Technology) include vt-d?

I'm at a loss. I've been researching current processors for an important project for some time now.

I need to know, if the xeon 5600s (Westmere EP) include vt-d (iommu/directed io/pci passing) because the system will run virtualized guests. This enables direct hardware access eg. pci passthrough, in xen for example.

It seems that the 5600s TXT should incorporate vt-d and that xeon 5600s should include vt-d as they are ramped up 5500s, but there is no conclusive answer anywhere. Intel's processor comparison only states that 5500s have vt-d and no TXT and 5600s have no vt-d but TXT.

I'd be really grateful if anybody could clear this up and possibly even provide a citation.

Thanks a lot.

Edit: Alternative: Can anyone report success in running Xen on a 5600 with working pci passthrough?

  • You must have the widest monitor on earth if you can actually read that table! – Mark Henderson May 18 '10 at 4:03
  • No, I scroll :(, but I occasionally copied the whole table to an openoffice spreadsheet when I was comparing all current cpu lines to the 6128 opteron ,). – deploymonkey May 18 '10 at 4:18

http://en.wikipedia.org/wiki/Trusted_Execution_Technology - Intel TXT includes Intel VT-d

This technology is coupled with VT-d (Intel Virtualization Technology for Directed I/O) which, among other things, protects certain areas related to TXT from DMA access.

  • Nice to read You again. Thanks for Your effort. Citation there, yes, but I've been there already. It says coupled, the graphics tell that vt-d would reside in the chipset and nowhere is the extent of coupling or feature incorporation mentioned. I mean thats intel, they even charge extra for blowing pixie dust up ones hot air vent duct ;) . Would You bet 1500$+ on intel marketingspeak with only weak mentions in the datasheets? (No pun or anything intended.) – deploymonkey May 18 '10 at 4:26
  • 1
    Haha, my favourite story was of the Althon XP and MP - you could short out two pins on an XP and it would become an MP. I never tried it (I forked out for full priced MPs) but it became an urban legend. Anyway, usually with those Intel Matrix's if one feature set supercedes another they only specify the superceded data. It's the same when purchasing the i7 processor, they don't indicate Intel VT, because it has a newer version or something. – Mark Henderson May 18 '10 at 4:33
  • That figures - for intel ;) I just remembered the Athlon pencil trick... – deploymonkey May 18 '10 at 5:41
  • Aaah, the heady days of showing off my Dual Athlon 260MP box at LAN parties :) – Vincent Vancalbergh Jul 16 '13 at 13:26

The real answer is provided here for anyone who is interested. In general vt-d is a chipset feature and ark.intel.com is wrong.


VT-d is a feature of the memory controller, which now happens to be in the CPU for Nehalem and later systems. For systems prior to Nehalem, you need support in the chipset. All CPU's require a MB BIOS that supports VT-d.

For example, a Q6600 is listed as having no VT-d support, which is correct. The CPU itself does not have any VT-d functions. However, if you put that CPU into a MB with a Q35 or a Q45 chipset, VT-d works perfectly well, as long as you have a BIOS update that turns on VT-d support.

The difference is with Nehalem and later CPUs, if support is listed as "no" in ARK, you cannot add VT-d support to the system through the chipset. If "yes" appears in ark, and you put this in a MB that supports VT-d, VT-d will work just fine.


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