T640 memory upgrade guide
24 DIMM slots across 12 channels (2 DIMM per channel), DDR4 at up to 2933 MT/s, rated to 3TB. This page works out what actually fits and what we would ship for the platform.
Platform facts
| Item | T640 |
|---|---|
| Processors | 2× 1st/2nd Gen Intel Xeon Scalable (Skylake/Cascade Lake), up to 28 cores each |
| Memory type | DDR4 RDIMM / LRDIMM |
| DIMM slots | 24 |
| Channels | 12 (2 sockets × 6 channels) |
| DIMMs per channel | 2 |
| Rated speed | up to 2933 MT/s |
| Max capacity | 3TB (largest supported modules) |
| Form factor | Tower / 5U rack-convertible |
Platform figures are the ones published on the T640 product page; channel arithmetic is JEDEC standard for the processor generation. Confirm against your board revision and BIOS before a large purchase.
Capacity: what fits with each module size
| Module size | 1 module per channel (12 modules) | Full population (24 modules) |
|---|---|---|
| 16GB modules | 192GB | 384GB |
| 32GB modules | 384GB | 768GB |
| 64GB modules | 768GB | 1.5TB |
| 128GB modules | 1.5TB | 3TB |
Fill every channel before adding a second module to any channel: a balanced population is what gives the platform its full bandwidth. The platform ceiling of 3TB is reached with the largest modules the board accepts - the table above shows the practical ceiling for each module size.
How we would populate it
- 1Start with 12 modules - one per channel - using the module size that lands closest to the capacity you need. This is the cheapest route to full memory bandwidth.
- 2If you need more capacity later, add a matched module to every channel (2 DIMM per channel) rather than filling only the free slots on one side: an unbalanced population loses bandwidth and can step the speed down.
- 3Match the module organisation and rank across the population. 2Rx4, 2Rx8 and 4Rx4 parts are not interchangeable on every board, and LRDIMM cannot share a channel with RDIMM.
- 4Buy at the speed the platform runs (up to 2933 MT/s). A faster module runs at the platform ceiling; a slower one pins the channel to its own speed.
Modules we stock that fit this platform
- 16GB DDR4-2666 RDIMM
- 16GB DDR4-2933 RDIMM
- 32GB DDR4-2133 LRDIMM
- 32GB DDR4-2666 LRDIMM
- 32GB DDR4-2666 RDIMM
- 32GB DDR4-2933 LRDIMM
Every module is checked against your order before dispatch; condition (new or pull) is stated line by line.
Frequently asked questions
How much memory can the T640 take?
The platform has 24 DIMM slots across 12 channels (2 DIMM per channel at full population), and is rated up to 3TB. That ceiling needs the largest modules the platform accepts; with smaller modules the practical ceiling is slots × module size, which is the capacity table above.
How many DIMMs per channel does the T640 support?
12 channels and 24 slots gives 2 DIMM per channel. Population matters: filling every channel with one module (12 modules) is the balanced starting point, and going to 2 DIMM per channel is what reaches the full slot count. Some platforms step the memory speed down at the higher population - confirm the population rules for your exact board.
What memory type and speed should I buy for the T640?
DDR4 RDIMM or LRDIMM at up to 2933 MT/s. The CPU generation on the platform (1st/2nd Gen Xeon Scalable (Skylake/Cascade Lake)) sets the ceiling; a faster module runs at the platform speed, and a slower module pins the channel to its own speed. LRDIMM is only needed where you want the highest capacity per module and the platform supports it.
Can I mix module sizes in the T640?
Usually yes at JEDEC speed, provided the organisation and rank are close enough for the platform to train, but a mixed population runs at the speed of the slowest module and can lose the balanced interleaving. For a new build, populate all channels with identical modules; mixing is for upgrades where the existing population is already fixed.
Do you supply memory tested for the T640, and how is it shipped?
Yes - modules are checked against your order (part number, capacity, organisation and speed read from the label) and shipped from the Hong Kong warehouse with full export documentation, typically 3-7 days by air. Condition - new or decommissioned pull - is stated line by line before you order, and every module carries a 1-year written warranty.
Send the population, get a quote
Tell us the T640 generation, the population you are aiming for and the quantity. We confirm the fit and quote against confirmed stock with the date the figure holds until.
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