Monday, September 5th 2022
![Intel ARC](https://tpucdn.com/images/news/intelarc-v1719085767169.png)
Resizable-BAR a Must for Arc "Alchemist," Stick with Other Vendors if you Lack it: Intel
The PCI resizable-BAR feature is an absolute must for Intel Arc "Alchemist" graphics cards to perform as advertised, to the extent that Intel recommends sticking to "other vendors" (NVIDIA, AMD), for those on machines that lack resizable-BAR or prefer it disabled. In our testing of the Arc A380, we found a big performance gap between resizable-BAR being enabled and disabled. The company said that while it is working on driver optimizations that improve performance for machines lacking resizable-BAR, its general advice for those on older platforms is to stick with other vendors.
Resizable-BAR enables the software to see the entire video memory of a graphics card as a single large addressable block, rather than through 256 MB apertures. AMD and NVIDIA's driver architectures have optimized their memory-management to cope with these apertures through the advent of PCI-Express, but Intel Arc hasn't. Its memory-management model relies on large bursts of memory transfers, for which it needs resizable-BAR. The performance penalty for lacking it could be as high as 40 percent. In related news, Intel Graphics confirmed that the Arc A770 will be available both in 16 GB and 8 GB memory variants at launch—which is still slated for Soonuary, 2022.
Sources:
PCGH, DigitalFoundry (YouTube), VideoCardz
Resizable-BAR enables the software to see the entire video memory of a graphics card as a single large addressable block, rather than through 256 MB apertures. AMD and NVIDIA's driver architectures have optimized their memory-management to cope with these apertures through the advent of PCI-Express, but Intel Arc hasn't. Its memory-management model relies on large bursts of memory transfers, for which it needs resizable-BAR. The performance penalty for lacking it could be as high as 40 percent. In related news, Intel Graphics confirmed that the Arc A770 will be available both in 16 GB and 8 GB memory variants at launch—which is still slated for Soonuary, 2022.
53 Comments on Resizable-BAR a Must for Arc "Alchemist," Stick with Other Vendors if you Lack it: Intel
They had DG1 based on iGPU to test drivers.
Someone pushed through the fabbing of Alchemist against inside Intel opposition.
It seems DG2 should have been a test bed, not a full range launch even if the yarns being spun to the tech press are true.
There's holes in the story and what they have said undermines confidence if you have development experience.
Lying to cover up wasting hundreds of millions of dollars is a plausible explanation of an ambitious product rushing to market fueled by hubris and personal ambitions. Well they didn't say they needed Re-BAR until they had the problem with Alchemist reviews in China I've used SAM without needing it off, from what I can see AMD white/black listing of titles means it works great. I know Nvidia appeared to be less committed, which justifies the SAM validation and feature marketing.
Now Intel Tom & Ryan need to explain the strategy they had to have older unmaintained game VRAM management code re-written.
AMD would have had developer feedback about the pain of apertures compared to a unified address space, but PCIE is optimised for 32bit addresses and the 64bit transition had OSes use compatibility hacks to minimise trouble with devices using physical addresses on 64bit OS.
So SAM was messing with the status quo, VRAM doesn't fit in 32bit and AMD could try it out on their platform taking advantage of controlling BIOS and all driver software involved.
They want to offer the same performance at a lower price and they have stated they are well aware of their position and the gamble it will feel like for consumers.
Reviews of the arc350 all have explored ReBar off and on so dont worry about that and articles have been posted of motherboardvendors being asked by intel to have rebar enabled by default.
Nice would be if motherboards could detect a gpu as an intel gpu and then activate rebar but maybe that is something for the future unless in the future rebar is just always an improvement/mandatory.
"It's your loss" - intel.
Possible end of support is a big question mark, I give you that. Also is whether these cards will have any collector value after that.
Personally, the only reason I can still see myself buying an A770 when it comes out is curiosity. But I'm also curious about Zen 4 and RDNA 3, so I might have to toss a coin. :D
Pretty much says it all. Why bother. This entire line up is aimed at low to mid range rigs but it can't run on the majority of them. They have rather effectively crippled themselves. Where will they find a market now? Pre builds will be afraid to touch them.
The reason why BAR is mandatory is simply because of it's narrowed memory bus on all these cards. So they really need everything they can get. And even cheat with it as 3d mark scores initially leaked with higher scores then when that driver feature is fiddled off.
I'm not saying it's a faillure but this will take quite some (expensive) generations before they can even catch up with last or latest gen of both Nvidia and AMD. Its a failed product. Lack of DX11 native is also a bummer.
A simple BIOS update would've been easier than switching platforms.
I actually tried to google it but I cant find bios updates that specifically mention it.
Heck all information is a bit nebulous regarding that, officially only amd 3000 and up support it but people managed to get it working on older stuff....but waht that depends on...hell idk.Amd/comments/t5cpox Honestly such a weirdly negative comment, its a failed product? how so? do you even know what their actual goal is here?
If the goal is to get people talking, to make sure everyone knows intel has gpu's coming, then I would say its a winner.
Maybe they will produce very little of these because it was only meant as a "hey guys, yep, we are doing this" product, and the next will be higher production.
or maybe this will actually be produced in good volumes, do well on newer titles, get solid drivers eventually and with a low price, will be an ok purchase.
And yes he's wise enough to know how to update the bios to the latest version...
To me the appeal of Arc is precisely its newness, anything is possible. Better support for older, non-resizable BAR platforms would be a high priority for me, though. I wanna pick up an A770 sometime, but i'd be using it with my X99-based PC.
:)
Well it's nice to see some honest transparency ;)
and this is rebar ;)
Sounds like they ultimately found a solution, in a sort of roundabout way, but for any other user with a CH7H who wants to try an A380, make sure you have any of the seven more recent BIOS versions installed first.
CH7H:
rog.asus.com/motherboards/rog-crosshair/rog-crosshair-vii-hero-model/helpdesk_bios/
CH7H Wi-Fi:
rog.asus.com/motherboards/rog-crosshair/rog-crosshair-vii-hero-wi-fi-model/helpdesk_bios/