With regards to the 3770, will the presence of active VT-d /vPro/TXT silicon in addition to the slightly lower stock clock speed significantly lower the overclocking headroom ?
As far as i can judge from the oveview post, aside from the inclusion of the extra features and slightly lower stock speed, theres not much difference between it and it's k variant, but without a benchmark to go by comparing the two i am unsure which chip to buy, and I would rather not buy a chip that looks good on paper, but which fails to OC to a reasonable degree compared to it's slightly more expensive cousin.
Only the K version has an unlocked multiplier, so for all practical purposes only the K can be overclocked (to any significant degree). If you want to overclock, you want the K version, and essentially no other considerations apply.
The VT-d and TXT features really have nothing to do with overclocking except that Intel, in its product segmentation wisdom, has made them mutually exclusive with an unlocked multiplier. I've never seen any kind of technical argument for this: it seems to be purely a case of different features for (presumed) different markets. Intel thinks VT-d and TXT are of interest to corporate / professional buyers who would never allow their systems to be overclocked, which is probably true; it doesn't think they're of interest to enthusiasts who do overclock, which may not be. (Why they don't have a top-of-the-line-with-all-the-boxes-checked model, I have no idea. Seems like it would sell).
Note, however, that VT-d is not the same as VT-x. VT-x is the basic hardware virtualization feature, and it is present in both K and non-K versions. This is generally all that is required for virtualization software that requires hardware virtualization, so as far as that software is concerned all the top CPU models (K and not) have that support. VT-d is virtualized IO
, also called an IOMMU
, which enables the virtualization of DMA devices, allowing for a more complete virtualization including isolation of devices (without enormous memory-copying penalties), and may be required to enable certain features in virtualization software.
Virtualization is incredibly useful for running more than one OS at the same time, whether it is to run a virtual server for testing server-side code without requiring a separate machine, testing code on multiple versions of Windows, or running a Windows box inside Linux (or vice versa). It's also handy if you have code you don't trust (whether it's potentially malicious or buggy): install it on a virtual machine and it doesn't matter how messed up things get, since you can just shut it down and start over with a fresh VM image. Virtualized IO extends that to hardware, enabling you to work with hardware or drivers you don't trust, or even multiple versions of a driver at the same time.