Thursday, August 5th 2021

Curious AMD Navi 21-based Graphics Card with 8GB Hits the Radar

AMD's 7 nm "Navi 21" silicon powers the company's Radeon RX 6800 series and flagship RX 6900 XT graphics cards. It's a big chip, competitive with NVIDIA's fastest GeForce RTX 30-series products, and AMD set 16 GB as the standard memory amount for all products based on this chip, despite its 256-bit wide GDDR6 memory interface. Komachi Ensaka spotted a curious-looking Navi 21 product with 8 GB of memory, on the UserBenchmark database. The card is slower than the desktop RX 6800, but found trading blows with the RX 6700 XT. Speculation is rife as to what it could be.

The most plausible theory is that it could be a prototype, with its user testing out UserBenchmark. The GeForce RTX 3070 Ti has a shaky performance equation with the similarly-priced RX 6800, and any attempt to close the gap between the RX 6700 XT and the RX 6800 would cannibalize the latter, unless that's exactly what AMD wants—a product competitive with the RTX 3070 Ti, but with a leaner bill of materials than the RX 6800 on account of the 8 GB memory.
Sources: Komachi Ensaka (Twitter), UserBenchmark Database
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32 Comments on Curious AMD Navi 21-based Graphics Card with 8GB Hits the Radar

#1
ixi
Cool, cool, but now give us APU with rdna2 :}.

Is there really a need between 6700xt and 6800?
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#2
RedelZaVedno
GDDR6 and HDM2 prices are skyrocketing atm... AMD doesn't surely wanna give up any profit margins on Radeon product. Has it chosen to give DIY market less vram?
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#3
lexluthermiester
btarunrSpeculation is rife as to what it could be.
My guess is a budget friendly version of the 6700 or a mobile version of same.
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#4
Valantar
lexluthermiesterMy guess is a budget friendly version of the 6700 or a mobile version of same.
6700XT is Navi 22, and both 6800m and 6700m are the same.

My guess: judging by availability, nearly all Navi 21 dice are good enough for 6900 XTs (those are relatively abundant, with 6800s and 6800 XTs being rare as hen's teeth from what I've seen). Most likely, the vast majority that fail to meet that criterium are too defective to become 6800s or 6800 XTs too - defective memory channels being relatively likely. So they might just push out a half-memory SKU for some niche application (OEMs?) to make use of those chips as well. Call it a 6800 LE? Though knowing OEM-special naming, it'll be called something very nearly indistinguishable from mainstream retail parts, despite being slower, like the "Radeon 570" (note the lack of "RX") found in a bunch of prebuilts for a time.
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#5
Chrispy_
I wouldn't be surprised to see this as OEM-only version of the 6800 - maybe a 6800LE? Uses otherwise unsellable Navi21 dies with yield issues affecting more than 2 of the memory PHYs.

8GB on a 128-bit bus is pretty lame but OEM-only stuff is often pretty lame - that is the world of i9 prebuilts running single-channel DDR4, after all. The customers don't know better, the OEMs don't care, and everyone gladly takes money that would otherwise be tossed in the trash at the uninformed buyer's expense.

Who knows how many CUs it has, but presumably with less bandwitdth than the 6700XT and similar performance, it problaby has a few more CUs to compensate the memory bottleneck - perhaps 48 CU compared to the 40 of the 6700XT....
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#6
lexluthermiester
Valantar6700XT is Navi 22, and both 6800m and 6700m are the same.
Ok, and?
Chrispy_128-bit bus
Oh I greatly doubt that one. The performance shown above would not be possible with 128bit memory or even 192bit.
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#7
Chrispy_
ValantarThough knowing OEM-special naming, it'll be called something very nearly indistinguishable from mainstream retail parts, despite being slower, like the "Radeon 570" (note the lack of "RX") found in a bunch of prebuilts for a time.
Oh this, for sure. It'll be the Radeon 6800 rather than the LE now you mention it....
lexluthermiesterOh I greatly doubt that one. The performance shown above would not be possible with 128bit memory or even 192bit.
Infinitycache would make it less of a hinderance than you'd think, and the 6700XT it's being compared to only has 192-bit, so what makes you think that would not be possible? It's already being done!
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#8
lexluthermiester
Chrispy_Infinitycache would make it less of a hinderance than you'd think, and the 6700XT it's being compared to only has 192-bit, so what makes you think that would not be possible? It's already being done!
Call it a hunch. There isn't enough information to get into an in-depth technical discussion, however 128 or 192 bit memory just doesn't seem plausible..
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#9
Valantar
lexluthermiesterOk, and?
You don't make a "budget friendly" version of a 335mm²-die GPU from 520mm² die rejects, even if those were otherwise unsellable. Or, well, if you're producing at the volumes of Nvidia, I guess you do, given the 20860 "KO" SKUs. But they generally produce 10x or more the chips that AMD does, and thus are likely to have 10x the amount of rejects. I would also be extremely surprised if they left half or more of the CUs disabled - and a budget friendly SKU with more CUs than the more expensive one? Nah, not happening. So we're left with something below the 6800 (at least in bandwidth/memory) and above the 6700 (in CU count). A perfect no man's land for an OEM-only SKU with a weird configuration.

And "a mobile version of the same" already exists, using a smaller die. Navi 21 in mobile is extremely unlikely - it's just too big.
lexluthermiesterOh I greatly doubt that one. The performance shown above would not be possible with 128bit memory or even 192bit.
But if they're not cutting down the bus, what would be the motivation for making this GPU at all? Just using less DRAM, reducing the BOM? I guess that's possible, but if so that would need to be a very high volume OEM order for that to make sense, as it likely wouldn't sell much in the DIY market.
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#10
Chrispy_
lexluthermiesterCall it a hunch. There isn't enough information to get into an in-depth technical discussion, however 128 or 192 bit memory just doesn't seem plausible..
Well it's 8GB so it cannot be 192-bit unless they use size-mismatched VRAM packages and AMD has never done that, only Nvidia.

For the absence of doubt:
I'm saying that 128-bit might be enough memory bandwidth to reach 6700XT performance levels, and 192-bit is what the 6700XT already uses.

If AMD were using 256-bit bus that would require a fully-functional die with all 8 memory PHYs working, and there's no way performance would be down at 6700XT levels with all of that extra bandwidth and presumably more than the 40CU that Navi22 (6700XT) comes with.
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#11
lexluthermiester
ValantarYou don't make a "budget friendly" version of a 335mm²-die GPU from 520mm² die rejects, even if those were otherwise unsellable. Or, well, if you're producing at the volumes of Nvidia, I guess you do, given the 20860 "KO" SKUs. But they generally produce 10x or more the chips that AMD does, and thus are likely to have 10x the amount of rejects. I would also be extremely surprised if they left half or more of the CUs disabled - and a budget friendly SKU with more CUs than the more expensive one? Nah, not happening. So we're left with something below the 6800 (at least in bandwidth/memory) and above the 6700 (in CU count). A perfect no man's land for an OEM-only SKU with a weird configuration.

And "a mobile version of the same" already exists, using a smaller die. Navi 21 in mobile is extremely unlikely - it's just too big.
Those are interesting points, but AMD has made unintuitive choices in the past that worked out for them.
ValantarBut if they're not cutting down the bus, what would be the motivation for making this GPU at all? Just using less DRAM, reducing the BOM? I guess that's possible, but if so that would need to be a very high volume OEM order for that to make sense, as it likely wouldn't sell much in the DIY market.
We don't have enough info to be making any sensible conclusions at all. However, as pointed out previously, the performance results shown in the OP are unlikely with a memory bus less that 256bit unless the GPU and memory clocks are bumped up dramatically, which is unlikely.
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#12
HD64G
Possibly a low-VRAM mobile version of 6800 or OEM GPU as others have already suggested.
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#13
TumbleGeorge
Chrispy_Well it's 8GB so it cannot be 192-bit unless they use size-mismatched VRAM packages and AMD has never done that, only Nvidia.
From Reddit:

Bouowmx
248d

Each 32 bits of memory bus connects to one package of GDDR, which is manufacturered in amounts of power of 2: 1 GB and 2 GB, as of now.
It is possible to have 8 GB on a 192-bit bus: 4x1 GB + 2x2 GB. But this would lead to non-uniform performance: the first 6 GB of memory can be accessed at full bandwidth, but the last 2 GB can only be accessed by 64 bits of memory bus (partial bandwidth)
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#14
Chrispy_
TumbleGeorgeFrom Reddit:
Yeah, you're quoting the Nvidia asymmetrical VRAM bus, common from the GTX460 1GB, 550Ti, 660Ti etc.
AMD has never done this and Nvidia probably won't any more as they lost a class action lawsuit in the most recent (and worst) implementation of it - the GTX970.
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#15
TumbleGeorge
Chrispy_Yeah, you're quoting the Nvidia asymmetrical VRAM bus, common from the GTX460 1GB, 550Ti, 660Ti etc.
AMD has never done this and Nvidia probably won't any more as they lost a class action lawsuit in the most recent (and worst) implementation of it - the GTX970.
I have not detailed memories from many years how make cards VRAM ATI/AMD and partners...Do you sure for all ATI/AMD was with symmetrical installed VRAM?
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#16
DeathtoGnomes
Taking bets on this new cards name, AMD RX 6789 XT or just plain AMD RX 6750. :D
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#17
yotano211
lexluthermiesterMy guess is a budget friendly version of the 6700 or a mobile version of same.
The 6800m is already a desktop 6700xt. Can confirm, I'm testing out a 6800m laptop for future usage.
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#18
Valantar
DeathtoGnomesTaking bets on this new cards name, AMD RX 6789 XT or just plain AMD RX 6750. :D
I'm kind of disappointed there isn't a 6950 this generation. I had a HD 6950 a decade ago, but now I'm down a full 50 with my new GPU :( They don't make them like they used to!
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#19
Dragokar
I would like to see a 6800LE with 8Gigs. I think that's a nice addition.
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#20
ixi
DragokarI would like to see a 6800LE with 8Gigs. I think that's a nice addition.
I miss the "LE" products. They had power, were cheaper :).
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#22
mechtech
ValantarI'm kind of disappointed there isn't a 6950 this generation. I had a HD 6950 a decade ago, but now I'm down a full 50 with my new GPU :( They don't make them like they used to!
lol ya

I was hoping for a 6850..........but with similar price
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#23
InVasMani
Possibly just a 6800 chip with half the memory? I mean if the yields are good enough to do so for AMD selling a card between the 6700 and 6800 would fill out a bit of a product gap and be called a RX6750 or something.
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#24
Hieu_Arbiter
btarunrThe GeForce RTX 3070 Super has a shaky performance equation with the similarly-priced RX 6800
wait, there is RTX 3070 Super on the market? really?
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#25
lexluthermiester
Hieu_Arbiterwait, there is RTX 3070 Super on the market? really?
No, there isn't. At least not yet..
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