Nvidia Ampere Discussion [2020-05-14]

Jawed

Legend
I've only looked at Cold War, Star Wars and Atomic Heart though. Overall SM utilization is usually somewhere around 20% during RT passes with the INT ALU pipe seeing lots of action.
I wonder if the INT instructions are address calculations: need to convert box and triangle indices into real locations in memory?
 

Kaotik

Drunk Member
Legend
Hopefully this ships with per-game profiles. AMD seems to be leaving it up to users to figure out when it makes sense to enable SAM.
It requires a reboot to change setting.
edit:
Also, there's really no reason to turn it off, only test I've seen where it would have been better to leave it off was Borderlands 3 at 1080p and 1440p, both apparently horribly CPU limited (same FPS on both resolutions, SAM on or off)
 

arandomguy

Regular

I'm not sure if this test is entirely conclusive either. There's some things I'd like to see looked at more in depth -

1) Actual frame time distribution.

2) How this affects VRAM. I wonder if a possible reason AMD chose to bring this feature in now and only with RDNA2 is partly due to the relatively large VRAM increase, and if a downside is more pressure on VRAM resources. This might be more VRAM usage, less VRAM available, or less "efficiency" in terms of management/flushing VRAM itself.

3) What happens over a much more prolonged play session as opposed to the typical short test sessions.

4) What if you do "multi task" more in terms of applications that also consume VRAM while gaming (or other GPU dominant tasks)?

5) Multi monitor scenarios, related to the above

6) Is there actually increased pressure on the CPU/system memory side?

7) Older DX9/OpenGL games

8) Fullscreen vs borderless/windowed

9) Non gaming GPU applications
 

Kaotik

Drunk Member
Legend
Looks like there's few other cases too, hadn't checked that particular review before. I still personally wouldn't bother rebooting because of that.

On AMD presently. There is no apparent reason why a driver can't handle the on/off state without a reboot.
At least this sounds to me like something you're not doing while Windows is up and running
https://docs.microsoft.com/en-us/windows-hardware/drivers/display/resizable-bar-support
For Windows Display Driver Model (WDDM) v2, Windows will renegotiate the size of a GPU BAR post firmware initialization on GPUs supporting resizable BAR, see Resizable BAR Capability in the PCI SIG Specifications Library.

A GPU, supporting resizable BAR, must ensure that it can keep the display up and showing a static image during the reprogramming of the BAR. In particular, we don't want to see the display go blank and back up during this process. It is important to have smooth transition between the firmware displayed image, the boot loader image and the first kernel mode driver generated image. It is guaranteed that no PCI transaction will occur toward the GPU while the renegotiation is taking place.0
 

DegustatoR

Veteran
At least this sounds to me like something you're not doing while Windows is up and running
https://docs.microsoft.com/en-us/windows-hardware/drivers/display/resizable-bar-support
The underlying h/w capability obviously require a reboot to reset as the size of BAR is set at system boot.
But the driver taking advantage of the capability is dynamic, and AMD driver does this right now as some titles are black listed from SAM in it.
I dunno why AMD thought that this can't be user controlled and I hope that NV will add the option into CPL and integrate it with their app profiles system.
 

Kaotik

Drunk Member
Legend
The underlying h/w capability obviously require a reboot to reset as the size of BAR is set at system boot.
But the driver taking advantage of the capability is dynamic, and AMD driver does this right now as some titles are black listed from SAM in it.
I dunno why AMD thought that this can't be user controlled and I hope that NV will add the option into CPL and integrate it with their app profiles system.
Is this blacklist confirmed somewhere? It doesn't sound right.
By default BAR is at 256 MB, and with Resizable BAR it's set to max VRAM, whatever that may be on each card. Surely you can't just turn it on/off at will after the fact, since by default everything assumes there's at least that 256MB BAR available?
 
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