The T640 is the T440's bigger sibling — a full dual-socket 2nd-gen Xeon Scalable platform in tower form, with twenty-four DDR4 slots to 3TB and the GPU headroom that made it a favorite for workstation-server hybrids. It is what businesses buy when they need R740-class capability without a rack to put it in.
One documentation quirk we disclose rather than hide: Dell's spec sheet prints the platform's memory speed as 'up to 2993MT/s' — an apparent typo for the 2933 MT/s this 2nd-gen Xeon SP platform runs elsewhere in Dell's own documents. Our table takes the conservative path, listing 2933-rated and faster modules; verify against your unit's configuration if the last speed grade matters to your build.
Spec sheet prints speeds up to 2993 MT/s - an apparent typographical variant of DDR4-2933 on this 2nd Gen Xeon SP platform. Only 2933-rated and faster modules are listed here; verify against your live configuration.
Up to two 2nd Gen Intel Xeon Scalable; registered ECC DDR4 only; also supports up to 12 NVDIMM-N (192GB max). Tower form factor.
Source: Dell official documentation
Operating speed depends on CPU generation and DIMMs per channel — Spec sheet prints speeds up to 2993 MT/s - an apparent typographical variant of DDR4-2933 on this 2nd Gen Xeon SP platform. Only 2933-rated and faster modules are listed here; verify against your live configuration.. Always verify against Dell's QVL for your exact configuration.
| Brand | Module | Capacity | Speed | Type | $/GB | Price | |
|---|---|---|---|---|---|---|---|
| A-Tech | B0C2FML23M | 64GB | DDR4-2933 | RDIMM | $8.06 | $515.96 | Buy → |
| A-Tech | KTD-PE429 | 64GB | DDR4-2933 | RDIMM | $8.28 | $530.11 | Buy → |
| A-Tech | B0BPN4L74H | 32GB | DDR4-2933 | RDIMM | $9.11 | $291.60 | Buy → |
| A-Tech | B0CGJFB4TG | 32GB | DDR4-2933 | RDIMM | $9.33 | $298.70 | Buy → |
| SK Hynix | HMAA8GR7AJR4N-XN | 64GB | DDR4-3200 (runs at up to 2933 here) | RDIMM | $9.36 | $599.00 | Buy → |
| Samsung | M393A8G40BB4-CWE | 64GB | DDR4-3200 (runs at up to 2933 here) | RDIMM | $9.98 | $639.00 | Buy → |
| A-Tech | MTA36ASF8G72PZ | 64GB | DDR4-3200 (runs at up to 2933 here) | RDIMM | $10.56 | $675.95 | Buy → |
| Samsung | M393A8G40AB2-CWE | 64GB | DDR4-3200 (runs at up to 2933 here) | RDIMM | $12.48 | $799.00 | Buy → |
Each scenario is priced from the cheapest compatible in-stock module at that capacity, at the timestamp above. Configurations never exceed the platform's 24 DIMM slots.
Speed behavior on this platform: Spec sheet prints speeds up to 2993 MT/s - an apparent typographical variant of DDR4-2933 on this 2nd Gen Xeon SP platform. Only 2933-rated and faster modules are listed here; verify against your live configuration. Faster-rated modules from the table above are safe — they operate at the platform's supported speed for your configuration rather than their label speed.
Paraphrased from Dell's official documentation. Anything the manual does not state is omitted here rather than guessed.
Buy for the T640 the way its dual-socket architecture wants: even counts split across both processors, 2933-rated modules as the conservative default (per the spec-sheet reading our table applies), and capacity sized to the machine's remaining life rather than its 3TB ceiling. The GPU-adjacent builds this tower attracts should note that model and dataset growth is memory growth — the upgrade that helps is usually RAM before it is a second accelerator.
As a 2nd-gen Scalable platform, the T640 drinks from the same abundant used-DDR4 pool as the R740, and the tower's forgiving thermals make it an even happier home for tested pulls. The one non-negotiable stays the same: verify the CPU tier before paying for speed grades the sockets will quietly downclock.
A last practical word on the T640's dual personality: if the tower serves as a GPU workstation-server, memory and accelerator budgets compete for the same approval, and memory usually deserves the first call — models and datasets page to disk long before compute saturates, and the live table prices the fix in hundreds rather than thousands. If it serves as pure office infrastructure, the T440's guidance applies scaled up: fill toward the workload, buy in even counts per socket, and let the 24-slot ceiling be comfort rather than target.
Before ordering at scale, reopen the spec sheet linked in the rules box — Dell's documents are living files, and for a platform with a known misprint in circulation, checking the source directly is worth the half a minute it costs.
Every specification in the rules box above was verified against the Dell document linked beneath it before this page went live — nothing is inferred from forum lore or reseller listings, and any field the document does not state is simply absent here rather than guessed. The compatibility table applies those verified rules mechanically to our tracked module catalog: generation must match, the module type must appear in the platform's allowed list, speed must meet the documented floor, and per-DIMM capacity must respect the stated maximum. What survives that filter is sorted by live $/GB — computed against true 1024-based capacities — and refreshed on the same rolling cycle as every price on this site.
Two honest limits worth stating. First, our catalog tracks the retail module market, not Dell's option-part universe — a module absent from the table is not declared incompatible, merely untracked; the rules box tells you what any candidate must satisfy. Second, a compatibility table is not a QVL: Dell validates specific part numbers against specific configurations, and the disclaimer above the table is not boilerplate but the actual final step. Use this page to find the market's honest price for compliant memory; use the vendor's QVL to bless the exact part before a production order.
T640s serve two masters: the office server room that never became a server room — where the tower's acoustics and 3TB ceiling let one machine be the whole infrastructure — and the GPU-adjacent crowd, who bought the chassis for its accelerator support and now find the memory, not the GPU, is what the models and datasets outgrew. Both upgrade paths run through the same DDR4-2933 market, one of the best-supplied segments in the shortage.
For dual-socket units, remember the platform's channel arithmetic when sizing: memory should be distributed across both processors' channels, which makes even module counts per socket the natural increments. The scenarios above respect the 24-slot ceiling; your CPU population sets how the sticks divide.
Dell's documentation puts the platform maximum at 3TB across 24 DIMM slots. Reaching the maximum requires the largest supported DIMM in every slot — most real upgrades target far less, which is what the live scenarios above price.
DDR4 RDIMM and LRDIMM at 2933 MT/s, per Dell's documentation. Consumer non-ECC and XMP/EXPO kits are not supported — every module in the table above is a verified ECC server part of the correct type.
The Dell documentation we verified does not spell out mixing rules for this platform, so treat identical modules per channel as the rule: mixed configurations at best run at the slowest common speed, and at worst fail population requirements. Check the platform manual for your exact loadout before mixing.
Yes — modules rated above 2933 MT/s downclock to the platform's supported speed and run normally, which is why the table marks them "runs at up to 2933 here". Modules rated below 2933 MT/s are excluded from the table because Dell does not list them as supported.
4× 64GB fills 256GB and leaves 20 of the 24 slots free for later growth. Fewer, larger DIMMs preserve expansion room; more, smaller DIMMs are sometimes cheaper per GB — the live table above lets you price both routes at today's numbers.
Used and refurbished DDR4 ECC is a rational choice for this platform — DRAM has no meaningful wear mechanism, and tested pulls from decommissioned fleets often undercut new pricing substantially. Run memtest86+ on arrival and watch ECC counters for the first weeks. For production fleets, new modules with warranty remain the conservative default.
We treat it as a typographical variant of 2933 MT/s — the standard DDR4 grade for 2nd-gen Xeon Scalable, and the figure Dell's equivalent rack platform (R740) states plainly. Our compatibility floor uses 2933; nothing in our table depends on the misprinted number.