Possible to enable VT-d when BIOS only enables VT-x?

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cpams322

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Dec 26, 2017
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Sorry if this is the wrong forum to post this in, I wasn't sure of the best one...

My CPU (Intel E8400) and Chipset (Q45/43) support both VT-x and VT-d (VT for Direct I/O) virtualization.

However, I have an older PC (Dell Optiplex 760) with the latest BIOS ever released for that (A16) and even though Virtualization is enabled in the BIOS, it appears to only enable VT-x but not VT-d. The BIOS does not have an option to specifically enable VT-d or VT-x, it's just a generic "enable virtualization" option.

But I need VT-d support (VT for Direct I/O) because I want to be able to use PCI passthrough in VMware.

Does anyone know if there is a way to enable VT-d when BIOS does not specifically allow for VT-d?
 
I'll be perfectly honest with you, I have no idea what you mean by "what hypervisor do you plan on installing?". I'm fairly new to VMs. I started with VirtualBox, but I need PCI passthrough support so I just started dabbling in VMware today.
 
Sigh, I guess what I am telling you is that my BIOS does not have the option to enable VT-d. It only has an option to enable virtualization in general. I know this to be 110% true because I know the A16 BIOS options on my PC like I know my own children. I have configured it at least 300 times at this point (no joke). lol But I have seen screenshots where the option is there on the A16 BIOS, but that was on different model mobos. Dell shipped these 760 MTs with different mobos (not sure how many, but at least 2 different mobos for sure). However, it appears the one I have (0M8558N) is the most common. It's also in the Tech guidebook for this model pf PC.

I have come to the conclusion (reading various sites) that the reason is this particular motherboard does not support it even though the Q45 chipset does and the CPU does.

So my question is, is there a way around it? A mod, a hack, whatever you want to call it. This is the true reason for my post.

I have a feeling this is going to require a BIOS hack at the very least.
 
If it isn't in the BIOS, then there's nothing that you can do. I couldn't find a custom BIOS for the OM858N motherboard; if you know which Dell motherboard meets your requirements, then swap it. Does the R230R support VT-d?
 
I have no idea if the R230R mobo will support VT-d. However, I first need to find a list of all the mobos that shipped with the Optiplex 760 MT and then see if I can compare them. It's hard to get a lot of info on the Dell forum. Lots of "experts" there but not much in the way of good meaty info when it comes to stuff like this.

Dell also has a program called CCTK that you can use to somewhat modify the BIOS (or something like that). However, I'm not sure 100% how to use it. Been fooling around with it and it does in fact show that my system "could" have the option for VT-d enabling. I made an exe file with the CCTK with just that setting on it and set it to "enabled". I'm assuming that what I have to do with it is flash the bios with it just as I do with the BIOS exe file. Not sure if it will work, though, seeing how it looks like it is my mobo that is stopping the option from appearing in the BIOS. I have another 760 MT I might test it on. Not sure how much I'm am willing to risk bricking the BIOS. I'll have to think about that while I look for other solutions...if any.
 
Thanks for pointing back to the CCTK page. I did not notice the videos and other info at the bottom of the screen. Hmmm, I may give this a try on the other system.

The other system has the same mobo, BTW.

I looked at the R230R mobos on ebay and I definitely won't be trying it. They don't have a PCIe x1 slot because it is a shorter mobo made for the Desktop model. I have the MT (Mini Tower) model. I'm sure it would fit, but I need the PCIe x1 slot.

Last night before I went to bed, I read a theory that it might not be the mobo (or a chip on it) dictating whether or not the VT-d option shows in BIOS. Rather that the BIOS might be programmed to only show the VT-d option if the processor model begins with a Q, signifying Quad core. Mine starts with an E, therefore no VT-d option. If true, I believe a relatively simple BIOS mod could solve this. But I'm not the guy to do it without step-by-step instruction lol. The Optiplex 760 MT, DT and SFF models shipped with five Q processors, Q9650 & Q9550, Q9400, Q8300, & Q8200 (USA).

If true (that's a big if), buying a Q9400 is cheap. Problem is the Qs have a 95W TPD (my E8400 is 65W TPD). Not sure if that extra 30W would create too much stress on the these old PSU or not. Dell PSUs are weak, this one's only 305W.
 
Looks like there were only 2 mobos for the MT model (0M858N and 0G214D). Supposedly, mine is the only one of the 2 that supports a Quad processor according to the post at https://www.dell.com/community/Desktops-General/Optiplex-760-MT-Processor-Upgrade/m-p/4263241#M948487

Therefore, the theory that it's the motherboard that dictates to the BIOS to enable VT-d might probably be incorrect.

The theory that the BIOS is programmed to only show the VT-d option if there is a Quad core CPU might hold water. I wish I could remember where I read that theory. I've been to so many sites this past week, by brain is spinning lol.
 
No, I did not try it yet. I may try it later today. Will let you know.

Going through the Technical Guidebook for clues to other solutions and looking for more on CCTK program operations.

Also need to clear the mess mother nature made outside last night.
 


OK, well, I decided to try the CCTK file on the other identical system before I go outside to deal with the ice.

No dice, unfortunately. In the CCTK file I created, I set 2 parameters:

1. Enable Virtualization
2. Enable VT-d

After I ran the file I created, I get the following in the log file...

2018/01/13 11:44:43 cctk - virtualization=enable
and
2018/01/13 11:44:43 cctk - The option 'vtfordirectio' is not available or cannot be configured
through this tool.

I actually ran the EXE file 2 times.

-In a user account using "run as administrator" to run the file and
- from the Windows Administrator account also using "run as administrator".
(Yes, I restarted the system even though it was not required.)

The system/BIOS on this (these) PC(s) simply does not want me to be able to have this option, even though the processor supports it. :pfff:

I'm convinced that a BIOS mod is needed. Or another solution. And I am going to find it!!! Or at least find a solid answer as to why I can never enable VT-d on these PCs. I'm really leaning toward the theory that it will only work with a "Q" CPU installed. But even if that is true, I bet a BIOS mod would also work.

Off to clear the ice :/
 
Right, I knew you were going to bring that up. 😛 So let me clarify my theory...

Theory:
VT-d option in A16 BIOS will only be visible if the 2 following conditions are met...

1. The CPU is a "Q" processor
and
2. The the "Q" processor supports VT-d technology.


Just a theory. But I believe it's highly likely.
 
I found out that the 0M858N motherboard does not support a 95W Quad core CPUs, only 65W Duo core CPUs. However, I did find an M858N on ebay that comes with a Core 2 Quad Q9400. So not sure if what I got was misinformation or if the seller put a quad in a mobo that can't support it just to make it look more enticing. :/

Also, I have confirmation from another 760 MT owner that his Optiplex 760MT BIOS Settings (with the 0G214D motherboard & Intel E8400 CPU) do not include the "VT for Direct I/O" option.

The 0G214D CPU is basically the same as the 0M858N as in it does not support a Quad core CPU, supposedly.

I have yet to find any other 760 MT mobo model #s other than the 0M858N and 0G214D. Dell support forum is of no help. They are not interested in discussing "legacy" equipment. I did find a post that listed a couple other mobo model numbers but after researching I found they are either non-existent or were for other form factors of the 760, not the MT.
 
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