LGA 3647 socket: CPUs, chipsets and cooler fit
LGA 3647 is the Intel workstation and server socket introduced in 2016 with the Xeon Phi and Xeon Scalable families. It has 3647 contacts in a 76.0 by 56.5 mm package with a two piece independent loading mechanism. Against the smaller LGA 2066 workstation socket with four channel memory, LGA 3647 is the large socket option with six channel DDR4 and up to 48 CPU PCIe lanes.
Quick facts
| Maker | Intel |
|---|---|
| Package type | LGA |
| Contacts | 3,647 |
| Package size | 76.0 × 56.5 mm |
| Introduced | 2016 |
| Status | Legacy |
| Memory | DDR4-2933 ECC, six channels, up to 2 TB |
| PCIe from the CPU | 48 PCIe 3.0 lanes from the CPU, plus platform lanes from C621 for storage and I/O |
| Cooler mounting holes | Board specific (narrow and square ILM heatsinks) |
| Replaces | None |
| Replaced by | None |
Overview
Boards pair LGA 3647 with DDR4 ECC memory up to 2666 MT per s in six channels. The Xeon W-3175X supports up to 512 GB across its memory slots on workstation boards that list the part. Speed stays at the board qualified limit, and population follows one DIMM per channel for full speed or two DIMMs per channel where the board allows it.
Like every large LGA socket, LGA 3647 trades consumer simplicity for expansion. The chip can be swapped within the board support list, cooling is part of the workstation chassis with vendor qualified air or liquid, and buyers choose core count with GPU and memory as one system. When a design needs dual socket servers instead of single workstations, server boards with the same contact count carry Xeon Scalable silicon instead.
Processor generations
| Codename | Marketing name | Years | Notes |
|---|---|---|---|
| Skylake-SP | 1st Gen Xeon Scalable | 2017 to 2018 | Server silicon with 8 to 28 cores, six channel DDR4-2666 and 48 PCIe 3.0 lanes, launched on C620 series boards in July 2017. |
| Skylake-W | Xeon W-3100 and W-3200 workstation | 2018 to 2019 | Workstation silicon with up to 28 cores and 48 PCIe 3.0 lanes, launched with C621 boards in 2018 and extended by the 28 core W-3175X in January 2019. |
| Cascade Lake-SP | 2nd Gen Xeon Scalable | 2019 | Server silicon with 4 to 28 cores, six channel DDR4-2933 and 48 PCIe 3.0 lanes, launched on C620 series boards in April 2019 with Optane persistent memory support. |
| Knights Mill | Xeon Phi x200 | 2017 to 2018 | Many core accelerators with 64 to 72 cores and MCDRAM, launched in late 2017 on LGA 3647 for HPC nodes. |
| Knights Landing | Xeon Phi x200 series | 2016 | Many-core HPC processors including Phi 7210, 7250 and 7290 with 16 GB MCDRAM, launched in June 2016 on LGA 3647 with DDR4. |
Chipsets for LGA 3647
C621 workstation
The workstation chipset for LGA 3647. Boards accept Skylake-W parts with a BIOS that lists the part.
| Chipset | Segment | Notes |
|---|---|---|
| C621 | Workstation | Workstation chipset for Xeon W-3175X single socket boards with six channel DDR4 and 48 CPU PCIe lanes. |
C620 series
The server chipset series for LGA 3647 (Purley refresh). Boards accept Cascade Lake-SP parts with a BIOS that lists the part.
| Chipset | Segment | Notes |
|---|---|---|
| C621 | Server | C620 series chipset for LGA 3647 server and workstation boards with six channel DDR4. |
C620 series server
The server chipset series for Purley boards. Boards accept Skylake-SP parts with a BIOS that lists the part.
| Chipset | Segment | Notes |
|---|---|---|
| C621 | Server | Server chipset for Xeon Scalable Purley boards. |
A large LGA workstation socket
LGA 3647 follows the workstation rule: the processor sits in a levered LGA socket with flat pads against spring contacts, so there are no pins to bend on the chip. Unlike soldered BGA laptop packages, the CPU can be swapped for another W SKU where the board BIOS lists it. The large 76.0 by 56.5 mm package uses a carrier frame during handling, which matters more at this size than on small desktop sockets.
The socket choice shapes the workstation more than buyers expect. LGA 3647 needs a C621 board with six channel DDR4 layout and power delivery rated for 255 W parts. The 28 core W-3175X works as a drop in where the board support list includes it. Compatibility still depends on firmware and power delivery, so a board that ships with a lower power W part may need validation before running the flagship.
Memory, expansion and cooling
Memory on LGA 3647 is DDR4 with ECC in six channel layouts. The W-3175X reaches DDR4-2666 with up to 512 GB across its slots. Population follows board rules at one DIMM per channel for full speed. Capacity and speed join the CPU as lasting choices, since ECC RDIMM pricing dominates many builds.
Expansion comes from 48 CPU Gen3 lanes plus C621 chipset lanes. The 48 lane W-3175X designs split lanes between multiple GPUs, NVMe RAID and 10 GbE networking, with the exact split fixed per board. Boards that need more than the CPU offers use the chipset lanes for SATA, USB and extra slots.
Cooling has no single retail answer on LGA 3647. The same socket spans lower power server parts to the 255 W W-3175X flagship, and the heatsink is drawn for that workstation with vendor qualified air or liquid. The large package needs even mounting pressure, so torque sequence follows the board maker specification rather than a generic cooler manual.
Where LGA 3647 designs are used
LGA 3647 covers high end workstations from 2018 through 2019: content creation, CAD, AI data prep and 3D rendering with single socket simplicity. The W-3175X scales to 28 cores with an unlocked multiplier for tuning where the board allows. System vendors qualify memory kits per board for the full six channel bandwidth.
Mainstream desktops use smaller sockets with fewer lanes and channels. LGA 3647 stays the workstation home of Skylake-W with C621. The socket versus chipset guide covers why workstation compatibility lives in board vendor lists.
CPUs on LGA 3647
26 processor pages in the database, newest first.
| Processor | Cores / threads | Base / boost | TDP | Launched |
|---|---|---|---|---|
| Intel Xeon Platinum 8253 | 16 / 32 | 2.2 / 3.0 GHz | 125 W | Apr 2019 |
| Intel Xeon Platinum 8256 | 4 / 8 | 3.8 / 3.9 GHz | 105 W | Apr 2019 |
| Intel Xeon Platinum 8260 | 24 / 48 | 2.4 / 3.9 GHz | 165 W | Apr 2019 |
| Intel Xeon Platinum 8260M | 24 / 48 | 2.4 / 3.9 GHz | 165 W | Apr 2019 |
| Intel Xeon Platinum 8268 | 24 / 48 | 2.9 / 3.9 GHz | 205 W | Apr 2019 |
| Intel Xeon Platinum 8270 | 26 / 52 | 2.7 / 4.0 GHz | 205 W | Apr 2019 |
| Intel Xeon Platinum 8276 | 28 / 56 | 2.2 / 4.0 GHz | 165 W | Apr 2019 |
| Intel Xeon Platinum 8280 | 28 / 56 | 2.7 / 4.0 GHz | 205 W | Apr 2019 |
| Intel Xeon Platinum 8280M | 28 / 56 | 2.7 / 4.0 GHz | 205 W | Apr 2019 |
| Intel Xeon W-3175X | 28 / 56 | 3.1 / 4.3 GHz | 255 W | Jan 2019 |
| Intel Xeon Phi 7235 | 64 / 256 | 1.3 / 1.4 GHz | 250 W | Dec 2017 |
| Intel Xeon Phi 7285 | 68 / 272 | 1.3 / 1.4 GHz | 250 W | Dec 2017 |
| Intel Xeon Phi 7295 | 72 / 288 | 1.5 / 1.6 GHz | 320 W | Dec 2017 |
| Intel Xeon Bronze 3106 | 8 / 8 | 1.7 / 1.7 GHz | 85 W | Jul 2017 |
| Intel Xeon Gold 6154 | 18 / 36 | 3.0 / 3.7 GHz | 200 W | Jul 2017 |
| Intel Xeon Platinum 8180 | 28 / 56 | 2.5 / 3.8 GHz | 205 W | Jul 2017 |
| Intel Xeon Platinum 8180M | 28 / 56 | 2.5 / 3.8 GHz | 205 W | Jul 2017 |
| Intel Xeon Silver 4116 | 12 / 24 | 2.1 / 3.0 GHz | 85 W | Jul 2017 |
| Intel Xeon Phi 7210F | 64 / 256 | 1.3 / 1.5 GHz | 230 W | Oct 2016 |
| Intel Xeon Phi 7230F | 64 / 256 | 1.3 / 1.5 GHz | 230 W | Oct 2016 |
| Intel Xeon Phi 7250F | 68 / 272 | 1.4 / 1.6 GHz | 230 W | Oct 2016 |
| Intel Xeon Phi 7290 | 72 / 288 | 1.5 / 1.7 GHz | 245 W | Oct 2016 |
| Intel Xeon Phi 7290F | 72 / 288 | 1.5 / 1.7 GHz | 260 W | Oct 2016 |
| Intel Xeon Phi 7210 | 64 / 256 | 1.3 / 1.5 GHz | 215 W | Jun 2016 |
| Intel Xeon Phi 7230 | 64 / 256 | 1.3 / 1.5 GHz | 215 W | Jun 2016 |
| Intel Xeon Phi 7250 | 68 / 272 | 1.4 / 1.6 GHz | 215 W | Jun 2016 |
Frequently asked questions
Which processors fit LGA 3647?
Xeon W-3200 parts such as the 28 core W-3175X. Server Skylake-SP and Cascade Lake-SP parts share the contact count but use server boards, and consumer Core parts do not fit.
Is LGA 3647 the same as LGA 2066?
No. LGA 3647 is far larger at 76.0 by 56.5 mm with 3647 contacts, while LGA 2066 is smaller with fewer contacts. The notch positions differ so the packages do not interchange.
What memory does LGA 3647 use?
DDR4 ECC Registered or Unbuffered DIMMs up to 2666 MT per s with ECC on the W-3175X. Six channels carry up to 512 GB on workstation boards that list the part.
How many PCIe lanes does LGA 3647 provide?
48 PCIe 3.0 lanes from the CPU for GPUs and NVMe, plus platform lanes from C621 for storage and I/O. Board wiring fixes the split between graphics slots and M.2 slots.
Sources and verification
- LGA 3647 on Wikipedia
- 2nd Gen Xeon Scalable processors, formerly Cascade Lake (Intel)
- Intel Xeon W-3175X Processor specifications (Intel)
- Intel Xeon W-3175X specs (TechPowerUp)
Facts last checked against these sources on . Page last edited on .