sTRX4 socket: CPUs, chipsets and cooler fit
sTRX4 is the AMD high end desktop socket introduced in November 2019 for Ryzen Threadripper 3000 processors with the TRX40 chipset. It carries 4,094 contacts in a 58.5 by 75.4 mm package with a screw actuated retention and a carrier frame, and it has carried Castle Peak HEDT workstations from the 24-core 3960X through the 64-core 3990X. Against the smaller AM4 desktop socket with two memory channels, sTRX4 is the large HEDT option with four DDR4 channels and 64 Gen4 lanes from the CPU.
Quick facts
| Maker | AMD |
|---|---|
| Package type | LGA |
| Contacts | 4,094 |
| Package size | 58.5 × 75.4 mm |
| Introduced | November 2019 |
| Status | Previous generation |
| Memory | DDR4-3200 ECC UDIMM, 4 channels, up to 256 GB |
| PCIe from the CPU | 64 PCIe Gen4 lanes from the CPU (56 usable), 88 total with TRX40 |
| Cooler mounting holes | Large TR4-SP3 mount (sTRX4, sWRX8, TR4 and SP3 compatible) |
| Replaces | TR4 |
| Replaced by | sTR5 |
Overview
Boards pair sTRX4 with DDR4 UDIMM modules with ECC where the board wiring enables it, up to 3200 MT/s and up to 256 GB across four channels. The CPU provides 64 Gen4 lanes with 56 usable for GPUs and NVMe, plus 16 Gen4 lanes from TRX40 for a platform total of 88 lanes. The ceiling stayed at DDR4-3200 across the generation, so memory choice follows board population rules with 4 by 1R kits at 3200 MT/s and 8 by 1R kits at 2933 MT/s. The 3990X with 256 MB of L3 needs validated firmware for boost to 4.3 GHz.
Like every large LGA HEDT socket, sTRX4 trades desktop simplicity for expansion. The chip can be swapped within the board support list, cooling reuses the TR4-SP3 mount with vendor qualified air or liquid for 280 W parts, and buyers choose core count with GPU and storage as one system. The socket sits alongside sWRX8 for workstations while sTRX4 serves high end desktops, and sTR5 carries the later Threadripper generations.
Processor generations
| Codename | Marketing name | Years | Notes |
|---|---|---|---|
| Castle Peak | Ryzen Threadripper 3000 | 2019 to 2020 | Zen 2 HEDT silicon with up to 64 cores and 64 PCIe Gen4 lanes, launched in November 2019 on TRX40 boards. |
Chipsets for sTRX4
TRX40 HEDT
The single chipset for sTRX4. Boards accept Castle Peak Threadripper 3000 with the shipping firmware.
| Chipset | Segment | Notes |
|---|---|---|
| TRX40 | Enthusiast | HEDT chipset for Threadripper 3000 with PCIe 4.0 and quad-channel DDR4 layouts. |
A large LGA HEDT socket
sTRX4 follows the large LGA HEDT rule: the processor sits in a screw actuated 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 Castle Peak SKU where the board firmware lists it. The carrier frame holds the large 58.5 by 75.4 mm package during handling, which matters more at this size than on small desktop sockets.
The socket choice shapes the HEDT build more than buyers expect. sTRX4 needs a TRX40 board with a quad-channel DDR4 layout, and 3200 MT/s speeds already ask for careful population across four channels. The 64-core 3990X launched in February 2020 as the flagship with 256 MB of L3, while the 24-core 3960X and 32-core 3970X arrived in November 2019 with the same socket and chipset. Compatibility still depends on firmware and power delivery, so a board that shipped with a 24-core part in 2019 needs validation before running a 64-core flagship.
Memory, expansion and cooling
Memory on sTRX4 is DDR4 UDIMM with ECC where the board routes it, in a 4-channel layout with up to 256 GB per socket. Population follows one DIMM per channel at 3200 MT/s for full bandwidth with 4 by 1R kits, while 8 by 1R kits run at 2933 MT/s and 8 by 2R kits at 2677 MT/s on the 3990X. Capacity and ECC join the CPU as lasting choices, since validated speeds matter more than headline memory clocks for rendering stability.
Expansion comes from 64 CPU Gen4 lanes with 56 usable plus 16 Gen4 lanes from TRX40 for NVMe RAID and high speed networking. HEDT boards split lanes between multiple GPUs, NVMe arrays and 10 Gb 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 reuses the TR4-SP3 mount on sTRX4, so existing large Threadripper coolers fit the same retention. The whole Castle Peak HEDT stack spans a 280 W envelope, and the heatsink is drawn for that desktop with vendor qualified air or liquid with liquid recommended for the 3990X. The large package with its carrier frame needs even mounting pressure, so torque sequence follows the board maker specification rather than a generic cooler manual.
CPUs on sTRX4
3 processor pages in the database, newest first.
| Processor | Cores / threads | Base / boost | TDP | Launched |
|---|---|---|---|---|
| AMD Ryzen Threadripper 3990X | 64 / 128 | 2.9 / 4.3 GHz | 280 W | Feb 2020 |
| AMD Ryzen Threadripper 3960X | 24 / 48 | 3.8 / 4.5 GHz | 280 W | Nov 2019 |
| AMD Ryzen Threadripper 3970X | 32 / 64 | 3.7 / 4.5 GHz | 280 W | Nov 2019 |
Frequently asked questions
Which processors fit sTRX4?
Ryzen Threadripper 3000 HEDT parts on Castle Peak, Zen 2, such as the 3960X, 3970X and 3990X. Threadripper PRO parts for sWRX8 do not work here despite the identical package.
Can an sTRX4 processor work in a TR4 board?
No. sTRX4 is physically identical to TR4 and server SP3 but electrically incompatible with both, so an older board cannot accept a Castle Peak chip.
Does sTRX4 use DDR4 or DDR5?
DDR4 with ECC where the board enables it, up to 3200 MT/s in 4 channels and up to 256 GB per socket with UDIMM modules.
How many PCIe lanes does sTRX4 provide?
64 PCIe Gen4 lanes from the CPU with 56 usable plus 16 Gen4 lanes from TRX40 for storage and expansion, with 88 total lanes on the platform.
Sources and verification
- Socket sTRX4 (Wikipedia)
- AMD Ryzen Threadripper 3990X specifications (AMD)
- Zen 2 Castle Peak Threadripper specifications (Wikipedia)
Facts last checked against these sources on . Page last edited on .