Incorrect GPU-Z ‘above 4G decoding support’ detection?

[4EvrYng]

In front of me I have EVGA 2080 Super FTW3 Hybrid Gaming card mounted in EVGA X299 Dark motherboard. In motherboard’s BIOS option for for ‘above 4G decoding’ support is set to -OFF-.

However, if I run GPU-Z, go to Advanced tab, pick PCIe Resizable Bar section from the list, and take a look at ‘Above 4G Decode enabled in BIOS’ under Resizable BAR Requirements it says -YES-.

Does anyone know what is going on please? Am I misinterpreting what GPU-Z is saying or GPU-Z has a bug?

 

[eidairaman1]

In front of me I have EVGA 2080 Super FTW3 Hybrid Gaming card mounted in EVGA X299 Dark motherboard. In motherboard’s BIOS option for for ‘above 4G decoding’ support is set to -OFF-.

However, if I run GPU-Z, go to Advanced tab, pick PCIe Resizable Bar section from the list, and take a look at ‘Above 4G Decode enabled in BIOS’ under Resizable BAR Requirements it says -YES-.

Does anyone know what is going on please? Am I misinterpreting what GPU-Z is saying or GPU-Z has a bug?

Resizable bar, check your bios. Mskr dure cdm is off and bar is on with 4G.

 

[4EvrYng]

Resizable bar, check your bios. Mskr dure cdm is off and bar is on with 4G.

It seems you misinterpreted what I said. I'm not asking how to turn on resizable bar (which doesn't apply to me anyway as I have 20 series card) but why GPU-Z seems to incorrectly report status of my 'above 4G decoding'.

 

[W1zzard]

Device Manager -> View -> Resources by Type -> Memory

Can you screenshot the list? Particularly the end of the list. Anything that's above FFFFFFFF ? that's what GPU-Z is scanning for in that test

 

[4EvrYng]

Device Manager -> View -> Resources by Type -> Memory

Can you screenshot the list? Particularly the end of the list. Anything that's above FFFFFFFF ? that's what GPU-Z is scanning for in that test

Here is screenshot attached ...

 

[INSTG8R]

Basically there are 3 requirements. No CSM(UEFI) above 4G coding enabled and have the BIOS option for BAR enabled.
Obviously your card doesn’t actually support it tho

 

[4EvrYng]

Basically there are 3 requirements. No CSM(UEFI) above 4G coding enabled and have the BIOS option for BAR enabled.

Like I already mentioned, I am not trying to figure out is my system meeting the requirements, I am trying to figure out why GPU-Z doesn't reflect my BIOS setting accurately.

 

[W1zzard]

Here is screenshot attached ...

Then you have Above 4G decode activated. Note the last 3 entries, which use a memory range above 4G.

 

[Tetras]

Motherboard ignoring BIOS options is not uncommon. In this case, I wonder if it's enabled for other reasons.

 

[4EvrYng]

Then you have Above 4G decode activated. Note the last 3 entries, which use a memory range above 4G.

It seems I will have to reach out to EVGA then as their BIOS option lets me choose do I want above 4G decoding and is set to off.

UPDATE: I’ve reached out to EVGA for a comment as above implies their BIOS is not working correctly when it comes to ‘above 4g decoding’ setting. In the meantime I’ve again captured device manager output, this time for both BIOS setting disabled and enabled (please see new attachments).

These captures imply EVGA’s BIOS -IS- working correctly after all. With 4G decoding enabled my 2080 Super and number of other devices are mapped above FFFFFFFF. With it disabled they are mapped below it. Thus, if I am correct, you might want to take a look again at how you determine is above 4G decoding enabled or not.

 

[W1zzard]

Great testing. Thanks!

But isn't the definition of "Above 4G Decode: off" = all devices must have their memory ranges allocated at an address below 4 GB ?
That's the whole point of it? That's also how it works on all but a few bugged motherboards.

 

[AusWolf]

You can turn it on in BIOS, and GPU-Z will detect it, but the GeForce 20 series doesn't support it, so the final state will always be "off" or "disabled".

 

[W1zzard]

You can turn it on in BIOS, and GPU-Z will detect it, but the GeForce 20 series doesn't support it, so the final state will always be "off" or "disabled".

You are talking about "Resizable BAR" I assume? Above 4G decode is supported

 

[AusWolf]

You are talking about "Resizable BAR" I assume? Above 4G decode is supported

Ah! I must have misread something. My apologies.

 

[4EvrYng]

Great testing. Thanks!

But isn't the definition of "Above 4G Decode: off" = all devices must have their memory ranges allocated at an address below 4 GB ?
That's the whole point of it? That's also how it works on all but a few bugged motherboards.

You are welcome I wouldn't know what exactly is happening and how exactly it is supposed to work. That is a great question EVGA should be answering so I hope they will reply to my reaching out but you too might want to ask them as you carry weight in the industry so they are much more likely to answer that to you than to me.

In the meantime, if there isn't universal official API call to determine is 'above 4G decoding' enabled, so GPU-Z indirectly deduces answer based on is there -anything- above 4G, would it be better to deduce it based on is there a -GPU- above 4G, especially because information is looked at in the context of -GPU- tool? Or when it is not 100% clear (something is above 4G but there is no GPU above 4G) status reported could be something like '? / maybe / not sure' rather than firm 'yes'?

 

[W1zzard]

if there isn't universal official API call to determine is 'above 4G decoding' enabled, so GPU-Z indirectly deduces answer based on is there -anything- above 4G

Correct

would it be better to deduce it based on is there a -GPU- above 4G

I don't think enabling Above 4G decode guarantees that the GPU is always placed above 4G. This is not a GPU-specific feature

 

[4EvrYng]

I don't think enabling Above 4G decode guarantees that the GPU is always placed above 4G. This is not a GPU-specific feature

True. That is why I suggested different reporting logic might be better for end user that doesn't know as much as you do. GPU is not mapped above 4G even though there is something above 4G = above 4G decoding not performed for GPU, rather than 'above 4g decoding is enabled, period'.

You see in my case on one system (see first post with screenshot) it is only Intel's management engine and stuff that is above 4G and I don't know does them being there constitute above 4G decoding enabled. On other system (see second post) it is also high definition audio controller but I don't know which one. One on my motherboard is -disabled- and that could be remnants from Win install -before- I disabled it, it is not showing up on first system. So just because it is there above FFFFFFFF it doesn't seem solid indicator, behavior is inconsistent.

 

[W1zzard]

Hmm ... I guess I could rename the option to "Above 4G Decode active for GPU", but then people might be looking for a way to activate that (there isn't)

 

[4EvrYng]

Hmm ... I guess I could rename the option to "Above 4G Decode active for GPU", but then people might be looking for a way to activate that (there isn't)

Yeah, picking phrasing that can't be misinterpreted by anyone is often very hard to accomplish ... maybe two+ lines would be better? One for system (yes or no when you are 100% certain, ? when you aren't) and other -per each GPU- telling is that GPU mapped above 4G?

 

[zxTheWolfxz]

I don't think enabling Above 4G decode guarantees that the GPU is always placed above 4G. This is not a GPU-specific feature

This doesn't seem to be the case with a Tesla K80, or am I missing something?

 

[W1zzard]

This doesn't seem to be the case with a Tesla K80, or am I missing something?

Just to clarify, you have "Above 4G decode" enabled, and GPU-Z shows it's disabled? Screenshot of device manager -> resources for the graphics card

 

[zxTheWolfxz]

I've just learned I'll have to have a Quadro card installed in my MB before I can load & use the K80.
I have an older Asus P7P55 WS supercomputer board. The manual says this will work.
I don't have a Quadro card laying around looking on eBay now for something cheap to test with.

When using NVIDIA® CUDA™ Technology with a Quadro™ series graphics card and Tesla™ series computing processor cards, install the Quadro™ graphics card to PCIe 2.0 x16_1 slot and the Tesla™ computing processor cards to PCIe 2.0 x16_2, PCIe 2.0 x16_4 and PCIe 2.0 x16_5 slots.

BTW it shows code 12 when used with my GTX 1060. No resources are free for this device.

 

[Shou Miko]

I've just learned I'll have to have a Quadro card installed in my MB before I can load & use the K80.
I have an older Asus P7P55 WS supercomputer board. The manual says this will work.
I don't have a Quadro card laying around looking on eBay now for something cheap to test with.

When using NVIDIA® CUDA™ Technology with a Quadro™ series graphics card and Tesla™ series computing processor cards, install the Quadro™ graphics card to PCIe 2.0 x16_1 slot and the Tesla™ computing processor cards to PCIe 2.0 x16_2, PCIe 2.0 x16_4 and PCIe 2.0 x16_5 slots.

BTW it shows code 12 when used with my GTX 1060. No resources are free for this device.

Wow awesome board, I got a Asus Maximus III Formula myself in my collection the seller said the onboard nic was wonky on Windows 10 but I haven't tested this out.

 

[zxTheWolfxz]

Wow awesome board, I got a Asus Maximus III Formula myself in my collection the seller said the onboard nic was wonky on Windows 10 but I haven't tested this out.

That's a nice board. I only use wireless so I wouldn't know about the nic, plus I have those disabled in bios since they are not in use to free resources.