Request: Smart Access Memory information

[bridgman]

That SAM thing is about the driver being able to put (texture)-data directly anywhere in VRAM instead of having to upload it (in multiple pieces) to a small aperture and then using a DMA engine to move it to its final location?

AFAIK uploads are normally handled by on-chip engines (GFX or SDMA) which are not affected by BAR size anyways. This is more about being able to access already-uploaded data in place via CPU rather than having to bring it down to system memory, update it then re-upload.

[marek]

One of the advantages of SAM is that it makes SDMA obsolete because the CPU can write to VRAM directly. I think this is the biggest performance uplift from SAM.

[alosarjos]

Asus Crosshair VI Hero (X370) + 1700 + RX5700 here. I don't see any option that sounds like it could be this. CSM is disabled, still getting vram_vis_size = 256 MB.

I just read that the option on the BIOS was recently added on a beta BIOS for X470+ chipset BIOS... So I'm guessing Asus X370 users ain't getting it

[mlau]

This is more about being able to access already-uploaded data in place via CPU rather than having to bring it down to system memory, update it then re-upload.

Even if you modify the data with the host cpu, you'd need to pull the data out of the card's memory over pcie into the cpu and back again; pcie cycles are *slow*, I cannot imagine
why someone would do that on a per-frame basis (then again I'm no graphics person and have desinged my last pieces of hardware 10 years ago).

[marciosr]

Ryzen 7 2700 + Asus ROG STRIX B350-F GAMING bios 5603 + RX 480 Arch Linux updated.

$ AMD_DEBUG=info glxinfo | grep vram
vram_size = 8192 MB
vram_vis_size = 256 MB
vram_type = 5
vram_bit_width = 256
has_dedicated_vram = 1

[doomie]

Ryzen 5 1600 + MSI B350M Gaming Pro + Sapphire Pulse RX 5700 + Arch 5.9.13

flipped a switch for crypto-mining

vram_size = 8192 MB
vram_vis_size = 8176 MB
vram_type = 9
vram_bit_width = 256
has_dedicated_vram = 1

odd that vis size still short? i wonder if there's another feature i need to look for? it's almost all there... that'd be a problem given it's not all directly accessible?

[nadro]

Ryzen 7 3800XT + MSI B350M Mortar + Radeon RX 580 8GB + Ubuntu 20.10 (with Kisak ppa mesa fresh)

$ AMD_DEBUG=info glxinfo | grep vram
vram_size = 8192 MB
vram_vis_size = 8192 MB
vram_type = 5
vram_bit_width = 256
has_dedicated_vram = 1

[slavikgenes]

Ryzen 5 1600 + MSI B350M Gaming Pro + Sapphire Pulse RX 5700 + Arch 5.9.13
...
vram_size = 8192 MB
vram_vis_size = 8176 MB
...
odd that vis size still short? i wonder if there's another feature i need to look for? it's almost all there... that'd be a problem given it's not all directly accessible?

Same here, difference is only 16 MB but it still strange. B450 Tomahawk + R5 2600 and Sapphire Pulse RX 5700XT.

Other way to check is:

>dmesg | grep BAR=
[ 3.074548] [drm] Detected VRAM RAM=8176M, BAR=8192M

[doomie]

Same here, difference is only 16 MB but it still strange. B450 Tomahawk + R5 2600 and Sapphire Pulse RX 5700XT.
...
>dmesg | grep BAR=
...

yep.

[FONT=monospace][COLOR=#000000][    0.998403] [drm] Detected VRAM RAM=8176M, BAR=8192M[/COLOR][/FONT]

gonna bother me til i learn what that's all about

[zxy_thf]

Ryzen 3900X + Asrock X570M Pro4 + Radeon RX 5500

vram_size = 8192 MB
vram_vis_size = 256 MB
vram_type = 9
vram_bit_width = 128
has_dedicated_vram = 1

There is "above 4G decoding" in my BIOS but the option greyed out. Maybe I should flash my BIOS from 1.80 to latest version first.