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
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.
32 Comments on Curious AMD Navi 21-based Graphics Card with 8GB Hits the Radar
Is there really a need between 6700xt and 6800?
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.
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....
860 "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.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.
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.
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.
If you want to check, here's the list: en.wikipedia.org/wiki/List_of_AMD_graphics_processing_units
I was hoping for a 6850..........but with similar price