Monday, September 5th 2022

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
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53 Comments on Resizable-BAR a Must for Arc "Alchemist," Stick with Other Vendors if you Lack it: Intel

#26
Rob6502TPU
ratirtSomething tells me it is not just drivers that suck here. The drivers are bad for sure but maybe this Arch is just really bad product. If Intel wishes to stay in the dGPU market they really need to buckle up and refine the architecture and make some improvements while they work on the drivers.
The whole story sounds like a project management failure with unrealistic scoping and aims.
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.
1d10tIntel are new player here and already give a middle finger to legacy platform.
Well they didn't say they needed Re-BAR until they had the problem with Alchemist reviews in China
Dr. DroYeah, I assume this will be a tricky one for Intel to fix. BAR optimization can introduce so many obscure bugs. It's no big deal with newer hardware, but a GPU like the A380 is definitely something I would use on an older machine which will not support this feature.
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.
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#27
64K
I don't think Intel needs to worry about people sticking to Nvidia/AMD. The vast majority are going to do it anyway. Even Intel's best A770 will be entry level in performance comparison when the next generation Nvidia and AMD GPUs arrive in a matter of months.
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#28
Snoop05
watzupkenI believe Intel enabled it for some older chipsets., though I am not sure about AMD. I know my B550 board supports ReBar via a BIOS update, just that I am not sure how far back did AMD enable this feature.
All the way back to 300 series AM4 boards
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#29
ZoneDymo
usinameIts not even cheap, its on same or close to the price of the competitor's cards in same performance level. For beta product this is not acceptable price. You also speak about how the ReBar is required and the new systems support it, but how many people actually will know about that, will update their BIOS if it is not implemented in their current BIOS yet and will enable it? A very small percentage in my opinion, people just plug and play. That is why, the reviews should show ReBar On/Off performance
Prices are not official/final yet.
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.
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#30
Denver
That's a really funny title, it sounds like they're doing so well that they can snub consumers.

"It's your loss" - intel.
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#31
AusWolf
RidiculousOwOProblem is, if I had a rig that supports that function, what's the reason NOT to buy a Radeon card?
Buy an Arc card just because it's "cheap"? Well, what about DX11 games and other games that Intel claims to lack optimisation?
And for a product like this, I don't know whether its driver is gonna be any good, and neither do I know whether this product would be soon abandoned and end support.
I don't think lack of optimisation will be a problem with the 700-series cards. The card can just muscle through any old game it hasn't been optimised for. You'll probably have 90 FPS instead of 110, which is not a big deal. It's a much bigger issue with the 500 and 300-series cards, though.

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
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#32
maxfly
I was just reading a thread where a dude was trying to get his a380 to work on his 2700x/320 or 370 rig. I forget the mb but it lacked rebar. He spent a week trying to figure out a way to work around the need for rebar to no avail. He ended up swapping it into a i5 rig.
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.
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#33
Snoop05
maxflyI was just reading a thread where a dude was trying to get his a380 to work on his 2700x/320 or 370 rig. I forget the mb but it lacked rebar. He spent a week trying to figure out a way to work around the need for rebar to no avail. He ended up swapping it into a i5 rig.
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.
buy completely different platform instead of updating bios, what a dedication
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#34
Assimilator
Snoop05buy completely different platform instead of updating bios, what a dedication
Commenting without reading "I forget the mb but it lacked rebar", what dedication.
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#35
Jism
ratirtSomething tells me it is not just drivers that suck here. The drivers are bad for sure but maybe this Arch is just really bad product. If Intel wishes to stay in the dGPU market they really need to buckle up and refine the architecture and make some improvements while they work on the drivers.
Arc is a bad product, period. They took quite some time in between announcing, releasing cards and such that you cant think of nothing else then the ARC gpu to be respinned a couple of times by now. Constant bugs, defects and what more spoiled the party.

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.
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#36
JMccovery
AssimilatorCommenting without reading "I forget the mb but it lacked rebar", what dedication.
Snoop05 is more than likely correct. If that 300-series chipset has a BIOS that supports Ryzen 3000 and 5000 CPUs, it has a BIOS that supports ReSize Bar/SAM.

A simple BIOS update would've been easier than switching platforms.
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#37
Assimilator
JMccoveryIf that 300-series chipset has a BIOS that supports Ryzen 3000 and 5000 CPUs, it has a BIOS that supports ReSize Bar/SAM.
No, it does not, because A320 does not get reBAR.
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#38
ZoneDymo
AssimilatorCommenting without reading "I forget the mb but it lacked rebar", what dedication.
Well without knowing what motherboard it is, either can be true, link me an 320 / 370 board that does not support rebar/sam after updating the bios I guess.
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.
AssimilatorNo, it does not, because A320 does not get reBAR.
Amd/comments/t5cpox
JismArc is a bad product, period. They took quite some time in between announcing, releasing cards and such that you cant think of nothing else then the ARC gpu to be respinned a couple of times by now. Constant bugs, defects and what more spoiled the party.

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.
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.
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#39
maxfly
The mb in question is an Asus ROG Crosshair VII Hero wifi. He knew going in that it didn't support rebar but spoke to an Asus engineer that said there was a possibility. So he gave it a try but failed.

And yes he's wise enough to know how to update the bios to the latest version...
Posted on Reply
#40
Dr. Dro
ratirtSomething tells me it is not just drivers that suck here. The drivers are bad for sure but maybe this Arch is just really bad product. If Intel wishes to stay in the dGPU market they really need to buckle up and refine the architecture and make some improvements while they work on the drivers.
The drivers are 100% the problem, and I feel like a lot of people are overlooking what a minefield is developing GPU drivers. I mean have you seen the sheer size of the AMD and NV drivers? It will take a long time for Intel to catch up, that's for sure.
watzupkenI don't know if this is a good or bad thing. ReBar is meant to improve performance in games, but as we can see, some games actually regressed in performance with ReBar enabled. It seems like Intel simply made a forward looking card where there is no DX 9 native support and also not for systems that don't support ReBar. I wonder what other limitations there are with the ARC series.
Performance regressions from usage of resizable BAR in AMD and NVIDIA graphics come from the fact that their drivers had long since been heavily optimized around the traditional 256 MB aperture, and widely employ game specific optimizations as well. It's not resizable BAR per se that causes the regression, changing the BAR size to smaller or larger can actually throw a wrench into code optimization and even cause issues that did not previously exist or do not occur with a standard size.
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#41
Hofnaerrchen
Best intel sells their GPUs to OEMs only, else it might get quite messy. They should do fine in office PCs. In the end this sounds like a product launch that is 20 to 30 years late but nothing you should do in 2022.
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#42
Assimilator
Dr. DroIt will take a long time for Intel to catch up, that's for sure.
That isn't and should never be the consumer's problem. Intel is making it their problem. That's not okay.
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#43
Dr. Dro
AssimilatorThat isn't and should never be the consumer's problem. Intel is making it their problem. That's not okay.
Agreed, but at the same time, they are being upfront about their deficiencies and that the software is incredibly raw should very honestly be expected that as a new player in the dedicated GPU space, Intel has a gigantic uphill battle that it must win all the while skirting around AMD's and NV's patents and everything.

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.
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#44
catulitechup
I dont care rebar only need where can buy arc



:)
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#45
mechtech
"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"

Well it's nice to see some honest transparency ;)

and this is rebar ;)
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#46
shovenose
Although my A380 was a horrible mess and I returned it I’m eagerly awaiting the A770 to replace my RX6600 if it’s a good price. I will put the RX6600 in my secondary PC which doesn’t support ReBAR. My primary PC does, so Arc should work fine. We will see.
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#47
AKBrian
maxflyThe mb in question is an Asus ROG Crosshair VII Hero wifi. He knew going in that it didn't support rebar but spoke to an Asus engineer that said there was a possibility. So he gave it a try but failed.

And yes he's wise enough to know how to update the bios to the latest version...
The Crosshair VII Hero and Hero Wi-Fi have supported Resizeable BAR since late 2020.

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/


Posted on Reply
#48
RedBear
Intel mentioned Resizable BAR as a requirement for optimal performance several months ago, even before the first ARC GPUs were released and testing promptly confirmed the performance degradation without ReBAR. The ironic thing is that it mostly hits people on older (before the series 400 mobos) Intel platforms, maybe Intel thinks it will prompt them to upgrade?
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#49
maxfly
AKBrianThe Crosshair VII Hero and Hero Wi-Fi have supported Resizeable BAR since late 2020.

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/


It also requires a 3000 or 5000 series cpu from what he said. His 2700x wouldn't work. He was unable to even get it to post with the a380 as the primary gpu.
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#50
gasolina
I think intel will release these gpu in november and drop support by the end of december 2023 . i would just bash all intel gpu since buying them meaning encouraging corps give us overpriced + unfinished products . If the arc 770 is 300$ and support up to 3 years then it's decent deal but intel is intel their product are shortlived
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