VT-d support on Z77 boards

[mikewse]

It has been mentioned previously that Asrock supports VT-d (virtualized I/O) on most Z77 motherboards.

But according to Intel's spec sheet:

the Intel Z77 chipset doesn't support VT-d.

How is it then possible for the motherboard to support it?

[profJim]

Re: VT-d support on Z77 boards

There are probably other Intel z77 chipsets that support VT-d.
The chipset in the link you provided only supports pci-e 2.0.
The cpu and motherboard must both support VT-d.
The Ivy Bridge and Sandy Bridge K model processors do not support VT-d.
A web search using: ivy bridge vt-d motherboard support should provide more information.

[mikewse]

Re: VT-d support on Z77 boards

Ok, so let me put it this way:
The Asrock Z77 Extreme4 has VT-d support.
What version of the Z77 chipset does it use?

[synack]

Re: VT-d support on Z77 boards

Its the northbridge (that is now "ON DIE" with Sb and IB) that does the vt-d not the chipset. You need to find a compatible CPU and a motherboard that has been configured to allow/enable the on CPU feature.

[mikewse]

Re: VT-d support on Z77 boards

Thanks, this sounds reasonable. Isn't it strange though that the Q77 chipset is speced as VT-d compatible while the Z77 isn't?


I've seen mentions of an Intel vt-d verification tool that tests whether full vt-d support is available (but haven't found a download).
Have you verified your Z77 boards with this tool?

[synack]

Re: VT-d support on Z77 boards

I have a K processor, so my processor doesn't support it. besides, I have no reason to care about vt-d. I do not need to pass through any hardware through any of my VMware servers. personally or professionally (I professionally manage a 8 host enterprise esxi cluster with 400 guests on them. personally 1 host with 5 guests)

vt-d breaks advanced features in vmware, for instance vmotion. (which is one of the best features ever). The limitations imposed by vt-d negate the purpose of having virtualization these days. and seriously though, who needs to pass though a gtx 680 to a single guest? lol.

mainly this is why support for vt-d is weak, there is very little desire to have it. Those who do need it,need it for very niche applications. Ones that can be solved by just not bothering with Virtualization for that one particular need.

I'm not saying you shouldn't use it, but that is the reason why it is difficult to find any information about a seemingly miraculous feature. And why it's so hard to find out what does and does not have it.

I suspect that it's an error on Intel's part to list the q77 express with vt-d = "yes", as a Q77 is essentially an H77 with vPro. H77 also lists vt-d as "no"
I've never seen a verification tool, but then again, I've never looked for one. I suspect it'll be one of the main VM OSs like citrix, vmware or KVM that has the tool.

[parsec]

Re: VT-d support on Z77 boards

Intel now tends to separate product features into groups, and there are few if any individual components that have all of them. For example, if you want the "K - Unlocked" CPU to OC, you must get a matching chipset board, but then you lose features like Vt-d, and many of the other more enterprise oriented types. Go in the other direction for the enterprise oriented features, and you lose the ability to OC and get only one SATA III port on the board. The reason may be simply marketing and the needs of the customer, but that split might just benefit Intel economically too.

[kpo6969]

Re: VT-d support on Z77 boards

Ok, so let me put it this way:
The Asrock Z77 Extreme4 has VT-d support.
What version of the Z77 chipset does it use?

If you update to the latest bios (P2.70) it is no longer supported. P2.50 and lower it should.

[mikewse]

Re: VT-d support on Z77 boards

mainly this is why support for vt-d is weak, there is very little desire to have it. Those who do need it,need it for very niche applications. Ones that can be solved by just not bothering with Virtualization for that one particular need.

Thanks for the insights. I'm building a new system and as I'm going to go deep into virtualization I'd like to keep my options open and get a system that can do VT-d. Maybe I won't use it in the end, but rather be safe than sorry.

If you update to the latest bios (P2.70) it is no longer supported. P2.50 and lower it should.

That's very interesting, and confusing :-P
Any insights why?

[mikewse]

Re: VT-d support on Z77 boards

There seems to be several different possible answers to this question.
Can we have some official word from Asrock staff in this matter?

[kpo6969]

Re: VT-d support on Z77 boards

I got confused re-reading it again myself so disregard my earlier post.

2.70
12/4/2012
1. Support UEFI PXE boot.
2. Modify VT-d Capability will be unsupported after flashing BIOS P2.50.

2.50
11/14/2012
1. Improve USB compatibility.

[synack]

Re: VT-d support on Z77 boards

Thanks for the insights. I'm building a new system and as I'm going to go deep into virtualization I'd like to keep my options open and get a system that can do VT-d. Maybe I won't use it in the end, but rather be safe than sorry.

You will soon figure out that the deeper into virtualization you go, the more you won't want vt-d. :)

While passing hardware I/O directly to a guest *seems* like a great idea for performance (the ONLY pro among many cons), The whole purpose of virtualization is to abstract the hardware from the software. Total abstraction gives you portability and reliability/high availability that you can't get from direct contact to hardware. for instance if you want to assign a NIC to a guest. that NIC can only be used by that one guest and no others. if you want to be able to migrate that guest to multiple hosts for high availability, you need to have spare unassigned NICs in each of the other hosts. so say if you have 3 hosts for redundancy, you would need to have 3 physical NICs, 1 assigned at any time and 2 just sitting around doing nothing. just for one guest!! A terrible allocation of hardware at any rate.

In fact I really can't think of any good use cases at all. Video? nope. SAS/SATA Storage? Nope... Fibre channel? maybe... but those speeds are too slow to saturate modern busses. so Nope. lol
NIC is really the only maybe I can think of...
What would you think you might use it for?

But I digress, and will let you come to those and other conclusions yourself :)

[mikewse]

Re: VT-d support on Z77 boards

Again, thanks for the insights, and for the time you put in to share them. I have read up on the different virtualization forums (vmware etc) and 'm well aware of the problems people are having with VT-d. It is quite possible that I will end up with the same conclusion as you in the end.

But this thread is not about whether I want to use VT-d or not. It is about whether Asrock is correct in claiming that their Z77 motherboards support VT-d, when Intel claims that the Z77 chipset doesn't (while other chipsets such as the Q77 do).

I'm still eager to hear from Asrock staff whether their Z77 boards fully support VT-d. (Or is this the wrong place to ask Asrock?)
I've read there are 50 tests in the VT-d validation suite and I expect a board that claims VT-d support to pass all of them.

[- wardog -]

Re: VT-d support on Z77 boards

(Or is this the wrong place to ask Asrock?)

Yes and No. Emily from ASRock does not per se frequent the forum as often as one would hope. Not IMO enough to call it "support' by any stretch of the imagination.

ASRock > Support Request Form

For people like you I'll direct them to the link above.

This is more and more becoming a User supported forum. Thus why you see Users such as the very knowledgeable and professionally experienced synack offering up valid posts on the subject.

If you'd be polite enough to post back the response from ASRock of your inquiry it would be appreciated. Though judging by your last post I'm not holding my breath of that happening.

[synack]

Re: VT-d support on Z77 boards

I'm still eager to hear from Asrock staff whether their Z77 boards fully support VT-d. (Or is this the wrong place to ask Asrock?)
I've read there are 50 tests in the VT-d validation suite and I expect a board that claims VT-d support to pass all of them.

If you don't believe the ASRock manual's statement of compliance, what difference would it make to have them repeat it here? just saying...
And No, you probably won't get a reply from ASRock here. If you do it'll be lucky.

I've read in other forums that ASRock z77 boards do in fact support vt-d. I haven't seen the results of the 50 item test myself so I cannot say "fully" supported.