Here's the thing, SAM is more than just resizable BAR [rBAR] support, it's also the OS and driver support on both the CPU and GPU side to take advantage of the fast paths that rBAR support allows for. Although resizable BAR support itself doesn't have any real "special sauce", there is legitimate special sauce here: because AMD controls the CPU and GPU side of things, they can add the optimizations that rBAR support allows for to their driver and ensure/validate that it will work on ALL Ryzen 5000/RX 6000 setups. As seen here, any other setup is kinda a pig in a poke whether the mobo will support turning rBAR on, and even if you do, your OS and drivers may or may not support enabling the applicable fast paths allowed by rBAR support. So yes, SAM theoretically can be supported on many more systems than just Ryzen 5000/RX 6000 combos, but if you want SAM right now on Windows (majority of gamers), you do actually in all probability need the Ryzen 5000/RX 6000 combo. Us Linux nerds can take advantage of SAM on more setups, but we're the exception, not the norm.
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Originally posted by QwertyChouskie View PostHere's the thing, SAM is more than just resizable BAR [rBAR] support, it's also the OS and driver support on both the CPU and GPU side to take advantage of the fast paths that rBAR support allows for. Although resizable BAR support itself doesn't have any real "special sauce", there is legitimate special sauce here: because AMD controls the CPU and GPU side of things, they can add the optimizations that rBAR support allows for to their driver and ensure/validate that it will work on ALL Ryzen 5000/RX 6000 setups. As seen here, any other setup is kinda a pig in a poke whether the mobo will support turning rBAR on, and even if you do, your OS and drivers may or may not support enabling the applicable fast paths allowed by rBAR support. So yes, SAM theoretically can be supported on many more systems than just Ryzen 5000/RX 6000 combos, but if you want SAM right now on Windows (majority of gamers), you do actually in all probability need the Ryzen 5000/RX 6000 combo. Us Linux nerds can take advantage of SAM on more setups, but we're the exception, not the norm.
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Originally posted by QwertyChouskie View PostHere's the thing, SAM is more than just resizable BAR [rBAR] support, it's also the OS and driver support on both the CPU and GPU side to take advantage of the fast paths that rBAR support allows for. Although resizable BAR support itself doesn't have any real "special sauce", there is legitimate special sauce here: because AMD controls the CPU and GPU side of things, they can add the optimizations that rBAR support allows for to their driver and ensure/validate that it will work on ALL Ryzen 5000/RX 6000 setups. As seen here, any other setup is kinda a pig in a poke whether the mobo will support turning rBAR on, and even if you do, your OS and drivers may or may not support enabling the applicable fast paths allowed by rBAR support. So yes, SAM theoretically can be supported on many more systems than just Ryzen 5000/RX 6000 combos, but if you want SAM right now on Windows (majority of gamers), you do actually in all probability need the Ryzen 5000/RX 6000 combo. Us Linux nerds can take advantage of SAM on more setups, but we're the exception, not the norm.
honestly for Intel stuff is extremly easy, all they have to do is flip the switch on motherboards to say that those stuff are working and existing and if AMD doesn't block them, Intel should be seen as CPUs supporting exactly same things as AMD in terms of SAM. For Nvidia they do simply need to write on driver side stuff that takes advantage of those instructions when they are availiable.Last edited by piotrj3; 13 December 2020, 07:21 PM.
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Originally posted by szymon_g View PostCould anyone explain it to me as if I was 5 what's the resizable bar etc? Why is it important?
Now, that window can be resized. This means the driver can just make it as big as the whole video memory, so it can directly access all of it. This simplifies the driver and allows for performance improvements like writing data and commands directly to the GPU.
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Originally posted by shmerl View PostWhat does BAR stand for?Test signature
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Originally posted by user1 View PostApparently, if you have "above 4g decoding" enabled in bios, that means you have resizable BAR support on Linux/AMDGPU. At least with ASUS, not all boards have this BIOS setting. I know that all or most ROG boards have this setting and some Prime boards have it as well, but my board (Prime Z390-P) doesn't have it.
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Originally posted by kripteks View PostI have gigabyte b550 aorus pro with the lastest beta bios ("Add Re-size bar option for AMD Smart Access Memory support").
I dont see amd sam option in bios, i have ryzen 3800xt , the "above 4g decoding" is here.
You can check for it working like this:
Code:> sudo dmesg|grep BAR= [drm] Detected VRAM RAM=8176M, BAR=8192M
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Makes me wonder how much of a difference SAM would make for this:
Swap on video RAM - ArchWiki (archlinux.org)
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