Intel Xeon W CPUs take Skylake Server to workstations


— 12:20 PM on August 29, 2017

Intel's Skylake-X CPUs put some of the best elements of the company's Xeon CPUs on the enthusiast desktop, but those chips miss out on a couple of features that many would consider mandatory for workstation-class builds. The lack of ECC RAM support from the X299 platform is the most pressing omission, but businesses might also want support for Intel's vPro suite of remote management tools. Some others might also want AVX-512 support with dual AVX-512 FMA units in lower-core-count chips, a feature that's hobbled on lower-end Skylake-X CPUs and missing entirely from Kaby Lake-X chips. Yet another class of user might want more PCIe 3.0 connectivity from the CPU than lower-end Skylake-X CPUs provide. 

  Base
clock
speed
(GHz)
Turbo
Boost
2.0 speed
(GHz)
Cores/
threads
AVX-512
FMAs/core
L3
cache
(MB)

PCIe
3.0
lanes

Memory
support
TDP Socket Price
W-2195 2.3 4.3 18/36 2 24.75 48 Four channels
DDR4-2666 with ECC
140W LGA 2066 TBA
W-2175 TBA TBA 14/28 19.25 TBA
W-2155 3.3 4.5 10/20 13.75 $1440
W-2145 3.7 4.5 8/16 11 $1113
W-2135 3.7 4.5 6/12 8.25 $835
W-2133 3.6 3.9 6/12 8.25 $617
W-2125 4.0 4.5 4/8 8.25 120W $444
W-2123 3.6 3.9 4/8 8.25 $294

Intel's new Xeon W family of CPUs should satisfy all of those users with a refreshingly consistent feature set. (Sorry, Skylake-X builders.) These single-socket workstation chips range from four cores and eight threads to 18 cores and 36 threads, and they're all built using fully-enabled Skylake Server cores. That means every chip gets four channels of DDR4-2666 RAM with ECC support, two AVX-512 FMA units per core, and 48 lanes of PCIe 3.0 from the CPU. Four of those lanes likely power the DMI 3.0 connection to the chipset, so final systems will likely have the same 44 lanes for I/O and peripherals as other Skylake Server parts. The only thing one seems to lose in the move to W-town is support for Intel's Turbo Boost Max 3.0 feature.

The entry-level Skylake-W parts are the most interesting of the bunch because they underscore the "scalable" in Xeon Scalable Processor. The Xeon W-2123 and W-2125 both offer four cores and eight threads, but they boast 8.25 MB of L3 cache—much more than the "natural" 1.375 MB of L3 per core from the Skylake Server microarchitecture. Those resource provisions suggest that Intel is able to selectively disable cores on its on-die mesh without disabling their associated L3 caches. These chips have 120W TDPs, and their only major difference is in clock speed: 3.6 GHz base and 3.9 GHz Turbo speeds for the W-2123, and 4.0 GHz base and 4.5 GHz Turbo for the W-2125.

Moving up the Xeon W product stack reveals more familiar faces. Intel will offer two six-core, 12-thread parts that differ only in clock speeds; a single eight-core, 16-thread part, a 10-core, 20-thread chip, a 14-core, 28-thread part, and an 18-core, 36-thread beast at the top of the stack. 12-core and 16-core members of the family are absent for now, but it's not a stretch to imagine they could show up down the line.

In another workstation-friendly touch, all Xeon W CPUs also offer support for up to 512GB of memory, as opposed to 128GB for Skylake-X parts. As we already noted, ECC RAM support is included in these CPUs, compared to the hard no-go one gets with Skylake-X.

While each Xeon W CPU uses the LGA 2066 socket that we know from the X299 desktop platform, these chips will require a new chipset and new motherboards to function. The C422 chipset is broadly similar to X299. It offers 24 lanes of PCIe 3.0, as many as 10 USB 3.0 ports, as many as eight SATA 6Gbps ports, and integrated Gigabit Ethernet. How those PCIe lanes, USB ports, and SATA ports are balanced in shipping products will depend on manufacturer implementations. Unlike X299, however, C422 includes support for Intel's vPro remote management suite and Rapid Storage Technology Enterprise 5.0 features.

The C422 chipset also includes an apparently new tier of Intel's Reliability, Serviceability, and Availability (RAS) features called Standard Workstation. We're seeking more information on what these features might include, but the Standard tier for Skylake Xeons includes Advanced Error Detection and Correction monitoring within CPU cores' integer units, as well as Single DRAM Device Corrections, or SDDC. Xeon W chips may also support PCI Express End-to-End CRC Checking for data integrity on those buses. Although it's in the Standard RAS tier for server CPUs, we doubt Xeon Ws support Ultra Path Interconnect Protocol Protection, if only because these chips don't use UPI.

Intel didn't annouce a release date for Xeon W CPUs, but given the availability of Skylake-X chips in the market already and the fact that Xeon W-compatible motherboards are already rolling out, we'd expect these chips to be widely available soon.

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