Well at present the assumption is that the RX 6900 XT will only have a 256bit Memory Interface.
This makes sense as it has 16Gbx8 (2GB) GDDR6 16.0Gbps (K4ZAF325BM-HC16) Memory Modules.
Now as a keynote., this does mean that the Memory Clock will be 2000MHz... as such on a 256bit Interface this will offer a total of 512GB/s Bandwidth (not the 448GB/s on the RX 5700 XT or RTX 3070).
This likely is actually enough Bandwidth... remember that Navi doesn't NEED massive Bandwidth like Ampere does.
The RX 5000-Series could've used GDDR5., AMD chose to switch to GDDR6 likely in no small part because it was expected of them. I mean they were already being slammed for using GDDR5 when NVIDIA was on GDDR5X., with claims that they didn't have enough bandwidth.
It was nonsense. Polaris and Navi can both have their Memory Underclocked to 1200MHz., this literally makes less that 2% Performance Difference... that's an effective drop of ~35% Bandwidth.
With little to no performance loss., the reason why said Memory is clocked the way it is... is because that's the Specification for the Memory being used; as it provides the best Latency.
I'd be surprised if the RX 6900 XT actually does need 512GB/s Bandwidth.
The thing here is what is AMD gaining for the RX 6000-Series by using the 16Gb GDDR6 Modules., and that's obvious.
60% Less Power Consumption from the Memory for the same Storage Capacity.
To put it into perspective., let's say AMD did a "Refresh" for the RX 5700 XT to use 16GB VRAM using the 16Gb Modules... not only would it have More Bandwidth, but you'd be getting double the Memory Capacity while only increasing the Cards Peak Power from 220w to 232w.
We also have to consider that the 16Gb Modules can still use a 512bit Bus., albeit only providing up to 768GB/s Bandwidth... still again that should be enough.
I'd say, don't get too hung up on such details.
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Now if you are curious about the actual line up., remembering that rumours at AMD is present "Re-Branding" again.
RX 6900 XT (80CU) [Est. Retail Price. £719.99]
RX 6900 XL (72CU) [Est. Retail Price. £639.99]
RX 6900 XE (64CU)*
RX 6800 XT (60CU) [Ext. Retail Price £479.99]
RX 6800 XL (54CU) [Est. Retail Price. £429.99]
RX 6800 XE (48CU)*
RX 6700 XT (40CU) [Ext. Retail Price £319.99]
RX 6700 XL (36CU) [Est. Retail Price. £279.99]
RX 6700 XE (32CU)*
RX 6600 XT (30CU) [Est. Retail Price. £229.99]
RX 6600 XL (27CU)*
RX 6600 XE (24CU) [Est. Retail Price. £179.99]
RX 6500 XT (20CU) [Est. Retail Price. £149.99]
RX 6500 XL (18CU)*
RX 6500 XE (16CU) [Est. Retail Price. £119.99]
Note Prices are merely speculative and clearly subject to change... but are based upon historic pricing from ATI / AMD.
* These Models are potential SKU Variants., but I don't think they will be part of the Retail Product Stack... possible OEM / Mobile Variants.
