Z170 OC Forumla 6 GPU detection on Windows 10

whiplashtony wrote: So I tried flashing to the latest BIOS and I tried playing with the TOLUD setting some more with 64 G of RAM.  Nothing worked.   I searched the entire interweb web and couldn't find anyone else experiencing this issue except for one guy - https://forum.ethereum.org/discussion/5137/issues-with-mobo-asus-z170-pro-gaming-cant-detect-6-gpus.  Username "karthunk" - Looks like the same issue.  I'm still unclear what TOLUD is doing exactly.  Why would the OS need to reserve RAM relative to the Video RAM - are they not independent?   I've accepted defeated.

Changing TOLUD can increase the amount of memory available for use in the "PCI Express Configuration Space". That area appears to be 256MB usually, but not guaranteed.

TOLUD must be decreased, not increased, to potentially increase the amount of memory available for "PEG addresses", more on that below.

I thought for a moment that this DRAM memory area may not be your problem, but I'm not sure.

Here's what my memory looks like in Resource Monitor:



We both have 16GB of memory. Compare your amounts of Standby and Free to mine.

My Free: 13405MB. Your Free: 328MB.
My Standby: 792MB. Your Standby: 11123MB.

I know, why is it like this? I don't have an answer for you. Your current TOLUD setting may be doing this, set that back to the default ASAP! This is a more complex subject that is not something we usually deal with.

Very simplified, there is DRAM memory reserved for the OS to deal with PEG addresses, where PEG is PCI Express Graphics attached. If there are too many PEG addresses to deal with in the DRAM memory reserved for that purpose, that is an out of resources condition.

If you want to read about this, go to page 23, section 2.3.3, of this document. A good picture of this is on page 24. Don't expect it to be easy:

http://www.intel.com/content/dam/www/public/us/en/documents/datasheets/3rd-gen-core-desktop-vol-2-datasheet.pdf

whiplashtony wrote: Thank you!  Yes, I'll keep reading about TOLUD, I think we agree that's probably the issue.   The bios only allows for dynamic, 2.5, or 3.5.  I have it set to 3.5 at the moment, and it's working with 5 cards.  I'm not quite sure how as that is over 16G of RAM ... I think my memory screenshot makes more sense now.  The standby memory is over 11G ram so 2.5 x 4 - and no idea on the other card.  I'm also not quite sure why my resource monitor for memory looks more like yours now - https://www.dropbox.com/s/3mfb1nkn88sdu18/Screenshot%202016-09-17%2000.04.45.png?dl=0.  Almost 12G free.   If I set it to dynamic, then Windows will recognize all the cards, up to 6 - but will not allocate resources.  So how can I set TOLUD, if I can't do so in the BIOS?  I noticed this TOLUD setting wasn't even mentioned or in the screenshots for book that came with the motherboard.     I guess I'll stick with 5, and start researching a board correctly about PCIE lanes before I go on any buying sprees.    Thanks again for all the help.

That is the problem, there isn't a TOLUD option in your board's UEFI, or most if not all boards of this type.

You lost me on this: "The bios only allows for dynamic, 2.5, or 3.5".

What option is that, in the BIOS?

If you haven't tried Dynamic yet, try it. Dynamic usually means the amount of space is adjusted to allow what is required to work correctly, providing more when necessary.

Changing TOLUD to a lower value in theory allows for a larger PEG memory space. But if you read that document, you'll see we may not really have control over how much memory will be given to the PEG memory space.