AMD Ryzen Threadripper PRO 3955WX socket: sWRX8
The AMD Ryzen Threadripper PRO 3955WX uses sWRX8, the 4094-contact LGA socket for Threadripper PRO workstations. It is a 16-core Castle Peak chip at 280 W for WRX80 boards with 8-channel DDR4 memory.
- Socket
- sWRX8
- Launched
- July 14, 2020
- Cores and threads
- 16 and 32
- Default TDP
- 280 W
- Codename
- Castle Peak
- Segment
- Workstation
- Clocks
- 3.9 / 4.3 GHz
AMD Ryzen Threadripper PRO 3955WX specifications
| Cores | 16 |
|---|---|
| Threads | 32 |
| Core architecture | Zen 2 (Castle Peak) |
| Clocks | 3.9 GHz base, up to 4.3 GHz boost |
| Cache | 64 MB L3, 8 MB L2 and 1024 KB L1 |
| Default TDP | 280 W |
| Manufacturing process | TSMC 7 nm FinFET |
| Memory support | DDR4-3200 ECC, 8 channels, up to 2 TB |
| PCI Express | 128 PCIe Gen4 lanes from the CPU |
| Integrated graphics | None (discrete card required) |
| Multiplier | Locked |
| ECC memory | Supported, RDIMM with ECC |
| Package | FC-LGA4094, socket sWRX8 |
| Cooler in the box | None, 280 W workstation heatsink required |
Motherboard and chipset compatibility
AMD Ryzen Threadripper PRO 3955WX needs a motherboard with a sWRX8 socket. The table shows which chipset series accept it.
| Series | Chipsets | Support |
|---|---|---|
| WRX80 workstation | WRX80 | Works out of the box |
Board makers publish a CPU support list for every model. Check it for your exact board before buying. Chipset details for sWRX8.
sWRX8 at a glance
| Type | LGA, 4,094 contacts |
|---|---|
| Package size | 75.4 × 58.5 mm |
| Introduced | July 2020 |
| Memory | DDR4-3200 ECC UDIMM, RDIMM, LRDIMM or 3DS RDIMM, 8 channels, up to 2 TB |
| Cooler mounting holes | Large TR4-SP3 mount (sTRX4, sWRX8, TR4 and SP3 compatible) |
What the Threadripper PRO 3955WX is
The Ryzen Threadripper PRO 3955WX is the sixteen core step in the Castle Peak workstation range that AMD listed on July 14 2020 for sWRX8 boards. Its Zen 2 cores run 3.9 GHz base with boost up to 4.3 GHz across 32 threads. Cache is 64 MB of L3 with 8 MB of L2 and 1024 KB of L1, and the TSMC 7 nm FinFET process balances clocks with core count.
Sixteen cores suit mixed workstation loads that split time between interactive modelling and background rendering. The 3.9 GHz base stays near the twelve core entry while adding four more cores, which helps compilation and simulation without giving up responsiveness. Eight DDR4 channels feed the cores with ECC, and 128 Gen4 lanes cover multiple GPUs and NVMe.
AMD rates the chip at 280 W default TDP with locked multiplier. The sWRX8 package carries 4094 contacts in a large LGA with carrier frame, and discrete graphics are required. The 90 C maximum operating temperature guides workstation airflow with vendor qualified heatsinks.
Socket and motherboard compatibility
The 3955WX fits sWRX8 on WRX80 with 8 DDR4 channels. Consumer sTRX4 operation with 4 channels needs a non-PRO chip, so PRO planning centres on WRX80 board choice. Firmware support for Castle Peak PRO must be installed from the maker page. The LGA socket uses three Torx screws in order with the orange carrier.
WRX80 boards for sixteen cores cover creator models with strong audio and networking to workstation designs with BMC and ECC validation. Power stages still target 280 W sustained, so dual EPS and solid case airflow remain requirements. Memory population with RDIMM modules follows one DIMM per channel for full bandwidth to 2 TB.
The sixteen core point often matches single GPU creators better than larger PRO parts. Buyers who use one strong GPU with fast storage gain little from 32 cores, while those who render daily outgrow sixteen cores quickly. The LGA, PGA and BGA: CPU package types explained guide places sWRX8 LGA handling against desktop sockets for builders new to Threadripper torque procedures.
Memory, PCIe and cooling
DDR4 to DDR4-3200 in 8 channels with ECC gives full bandwidth to 2 TB. Primary slots first per manual, with RDIMM versus UDIMM validated per board. Larger kits need board validation for LRDIMM versus 3DS RDIMM. Memory speed past 3200 MT/s helps only where the board qualifies it, since workstation stability favours validated speeds.
PCIe from the CPU gives 128 Gen4 lanes for a primary GPU at by 16, a second GPU and Gen4 SSDs at by 4. Chipset lanes add SATA, USB and extra slots. Cooling needs a 280 W workstation tower or liquid unit, because sixteen high clock cores concentrate power under all-core loads. No box cooler is included.
ECC joins the CPU as a lasting choice. Boards that route ECC with RDIMM correct single bit errors in long jobs, which matters more than headline memory clocks for workstation stability. Population with eight matched modules beats mixed kits for bandwidth and timing.
Upgrade paths
On WRX80 the nearby steps are the twelve core AMD Ryzen Threadripper PRO 3945WX for higher base clocks at lower core count and the 32-core AMD Ryzen Threadripper PRO 3975WX where rendering scales. Many owners gain more from GPU or memory steps first. Filling 8 channels and adding fast NVMe help large projects without a chip swap.
Moving to HEDT on sTRX4 changes channels and lanes with a board change for desktop oriented builds without ECC needs. For most 3955WX owners the value order is memory to 8 channels, then GPU, then a core step on the same sWRX8 socket where jobs scale.
Used buyers check firmware first. A WRX80 board that shipped with a sixteen core part in 2020 may need no update for another Castle Peak PRO, but a jump to Chagall PRO 5000WX needs a firmware update that adds the new IDs. The existing AMD Ryzen Threadripper PRO 3995WX shows the 64-core ceiling on the same socket for reference.
Frequently asked questions
What socket does the Threadripper PRO 3955WX use?
Socket sWRX8 (LGA 4094) on WRX80 with 8 DDR4 channels. It needs Castle Peak PRO firmware support and does not work in sTRX4 boards.
What memory does the 3955WX use?
DDR4-3200 ECC in 8 channels to 2 TB, with RDIMM, LRDIMM and 3DS RDIMM on most boards. One DIMM per channel gives full bandwidth.
How many cores does the 3955WX have?
Sixteen cores and 32 threads at 3.9 GHz base and up to 4.3 GHz boost, with 64 MB L3 and a 280 W TDP for mixed workstation work.
Is the 3955WX good for gaming?
It runs creation work with a discrete GPU, but single GPU gaming needs are served better by desktop parts with fewer channels. High clocks help interactive tasks, while board cost and 280 W cooling exceed gaming needs.
Sources and verification
- AMD Ryzen Threadripper PRO 3955WX specifications (AMD)
- Socket sWRX8 - 4094 contacts and WRX80 (Wikipedia)
- Zen 2 Castle Peak workstation CPUs (Wikipedia)
Facts last checked against these sources on . Page last edited on .