Sorry, I was jumping a gun a bit and
not taking the end of August rumors about the upcoming Threadripper chipsets with a grain of salt. The again, my post was pure speculation anyways.
Supposedly there'll be three chipsets: TRX40 with 4 channels as usual, and TRX80 and WRX80 with 8 channels, with the WRX being for workstations with ECC & RDIMM, but no overclocking support.
There's no doubt that 8 channels would require a new motherboard with one of the new "80" chipsets. What is less clear whether (and for which lines - HEDT or WS; 4 or 8 channel CPU SKUs) there would be backward compatibility if you were willing to settle for 4 channels, no official ECC support and RDIMMs having no chance of working.
I doubt the chipsets would be different silicon or have differences in functionality (of the chipset itself), seeing as how Threadripper is a relatively low volume product. Instead the "chipset" designations would be useful in motherboard names and marketing material to signal which boards support which functionality.
(To add to my speculation: With the "40" and "80" numbering AMD would leave room for new chipsets or versions by just incrementing the ones digit.)
*
With the way AMD seems to have used up most of the high 3000 series numbering with mainstream Ryzen, I was thinking maybe they'll go for a different numbering for 3rd gen. Threadripper (also to differentiate it more). Maybe:
- (7002 series: 2nd Gen EPYC)
- 6003 series: 3rd Gen Threadripper Workstation (support 8-ch. registered & ECC memory)
- 5003 series: 3rd Gen Threadripper HEDT (4-ch. memory, supports overclocking)
It would make a lot of sense at least for the WS parts.
Then, to make the SKU numbering really easy to decode, just put the number of cores in the middle two digits: 5243 would be a 24-core 3rd gen HEDT Threadripper. Will work as long as they have less than 100 cores (which I doubt will happen on desktop anytime soon, since frequencies would suffer too much), and until they make it to the 10th generation.
Two variants with the same number of cores (maybe with different cache amounts) can have a +1 added to the "number of cores" of the better one - it's unlikely they'll ever release TR CPUs with an odd number of cores.
Alternatively, if they didn't feel like segmenting the workstation features in a line of their own, they might make the CPU split according to the number of memory channels supported: 6003 for 8-channel, 5003 for 4-channel. If you put either in a workstation board, you'd get ECC & registered memory. If you put either in a HEDT board, you could overclock.
(I suppose they could also go for 63xx and 53xx series, but I like the symmetry with the EPYC numbering.)