Veteran discoverer KOMACHI_ENSAKA has unearthed multiple Eurasian Economic Commission (EEC) listings that involve various chipsets, such as X299R, X299G, X499 and X599. As denoted by the "X" suffix, the lot of unannounced chipsets are of the HEDT (high-end desktop) nature.
Starting with the obvious, the X299R and X299G chipsets are most likely Intel's property. For a start, Intel has already registered the X299 (Basin Falls) chipset for its HEDT processors. Naturally, any iterations of the X299 chipset would also belong to Intel, too. The chipmaker's most recent client roadmap hints that the upcoming Cascade Lake-X (CLS-X) chips will fit into LGA 2066 motherboards with the X299 chipset. Intel is rumored to launch a spanking new chipset, codenamed Glacier Falls, for the Cascade Lake-X parts.
The next step up would logically be X399. However, AMD was a step ahead of Intel and reserved the X399 designation before Intel could. If we have to take a wild guess, the "R" suffix in X299R could stand Refresh as in X299 Refresh. It's not impossible that the X299R or X299G chipset might, in fact, be the Glacier Falls chipset that we've heard about.
|Chipset||Manufacturer||Code Name||Socket||Release Date|
|C621||Intel||Lewisburg||LGA 2066||July 2017|
|X299||Intel||Basin Falls||LGA 2066||May 2017|
|X99||Intel||Wellsburg||LGA 2011-V3||August 2014|
|X79||Intel||Patsburg||LGA 2011||November 2011|
|X58||Intel||Tylersburg||LGA 1366||November 2008|
On AMD's end, the X399 chipset is still going strong after two years. Thanks to AMD's firm commitment to its existing sockets, both the first- and second-generation Threadripper processors have passed through the X399 chipset. To this day, only a handful of motherboard manufacturers launched refreshed X399-based motherboard for the Ryzen Threadripper 2000-series parts. Perhaps they knew about AMD's plans for a new chipset and opted to save their new designs for X499 instead. AMD has beaten Intel at its own game before, so it's feasible that AMD probably has dibs on X499 as well.
A couple of months ago, Intel revealed its 28-core unlocked Xeon W-3175X processor which rests on the enterprise-grade C621 chipset, codenamed Lewisburg. There were rumors that the C621 chipset would bear the X599 moniker. Fast-forward to the present day, and there still hasn't been any official confirmation on the topic. Motherboard options for the Xeon W-3175X are quite limited as only the Asus Dominus Extreme and Gigabyte C621 Aorus Xtreme are on the market. EVGA is probably putting the final touches on its SR-3 Dark, while we haven't heard anything from ASRock or MSI on the C621 front.