Dell PowerEdge R640 vs R650 — 1U Rack Server Comparison

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The 1U tier is where telecom, colocation, and edge-compute teams live. Density matters. Power matters. Dense rack positions in Cairo’s Smart Village and Dubai’s Equinix-DX facilities are billed per rack-U per month, so every millimetre of chassis efficiency shows up on the bill. The R640 was Dell’s 14G flagship 1U; the R650 is the 15G successor. Here is how they line up.

Side-by-side specs

Attribute	R640	R650
Generation	14G (Skylake / Cascade Lake)	15G (Ice Lake-SP)
Released	July 2017	March 2021
Form	1U	1U
CPU sockets	2	2
Max cores per socket	28 (6258R)	40 (8380)
Memory ceiling	3TB DDR4	8TB DDR4 (LRDIMM)
DIMM slots	24	32
Memory speed	DDR4-2933 max	DDR4-3200 native
Channels per socket	6	8
PCIe	Gen 3	Gen 4
Drive bays	8-10 SFF	8-10 SFF
NVMe lanes	Up to 10× PCIe 3.0 x4	Up to 10× PCIe 4.0 x4 native
OEM EOS / EOSL	No fixed date published by Dell (support per service tag)	No fixed date published by Dell (support per service tag)

The 1U thermal question

Every 1U server engineer knows: cores-per-watt is the real constraint in this form factor. R640 chassis is rated to 205W TDP CPUs (Platinum 8280, Gold 6248R) as a hard ceiling. R650 chassis carries a 270W TDP ceiling. That matters when you spec a Platinum 8368 (38 cores, 270W) — it only fits Dell’s 15G and newer.

Quick test: pull your BIOS fan-curve log from one R640 under 80 % load. If you see fans sustained above 50 % PWM, you are already thermal-limited. The R650 gives you headroom back.

NVMe — the real win

R640 offered up to 8 NVMe bays out of 10 in the universal chassis, or all 10 in the all-NVMe chassis, attached directly to the CPUs rather than through the PERC H740P. In practice most production R640 fleets shipped as 10× SAS SSD, not NVMe-dense.

R650 delivers 10× NVMe direct-attach natively when specced with the full-NVMe backplane. PERC H755N NVMe RAID is offered on the 8-bay backplane; the 10-bay NVMe backplane is direct-attach. Representative R650 NVMe PNs in the ICD catalogue: 0D4GH, 0MNMV.

Memory — 33 % more slots

R640 maxes at 3TB DDR4 across 24 DIMMs. R650 takes up to 8TB DDR4 (LRDIMM; 2TB with RDIMM) across 32 DIMMs — that extra memory channel per socket pays off in memory-bandwidth-heavy workloads like in-memory databases, Redis clusters, and large-page virtualisation hosts.

Cross-generation DIMM use: 2933 MHz RDIMMs (Dell PNs 370-ADVZ, 370-ADWK, 370-AEOI) will train on R650 at 2933 speed if mixed with 3200 sticks. Pure 3200 MHz population (PNs 6VDNY, 74FPM, 75X1V) is the right spec for a greenfield R650 build.

RAID controller generations

R640: PERC H330 (entry), H730P (mid), H740P (flagship), HBA330 (pass-through). PERC 10 family PN for 14G: 0878M.

R650: PERC H345/H355/H755/H755N/HBA355i — the PERC 11 family with tri-mode (SAS/SATA/NVMe) support. The HBA355i pass-through card has replaced HBA330 as the default SDS / Ceph / vSAN platform.

Power profile

R640 PSU: 495W / 750W / 1100W / 1600W Titanium. R650 PSU: 800W Platinum / 1100W Titanium / 1400W Platinum / 1100W -48 VDC. The 1400W ceiling is what enables dense NVMe + 270W dual-CPU builds without hitting a wall.

Sample ICD-supplied R640 PSUs: 061XT, 0G34N, 1JDDV, 1Y45R, 38GYJ. R650 higher-end: 0CYHH, 1CW9G.

Workloads where R640 is still right

Edge appliance racks where each site runs 1–2 servers and refresh churn is not worth the logistics.
Legacy VMware vSphere clusters still on ESXi 7.x — R640 is fully qualified for that release.
Colocation customers paying per rack-U where a working refurb R640 beats a refurb R650 on pure ROI until NVMe density or core count forces the jump.
AD/DNS/DHCP infrastructure nodes — workload so small the CPU generation is invisible.

Workloads that demand R650

New virtualisation consolidation projects — 40 cores per socket hits a density target R640 never could.
NVMe-tier storage for vSAN OSA or ESA, or for Oracle Exadata-style tiered layouts.
Light GPU-attached inference nodes — up to three 75W single-width GPUs; H100/L40S cards do not fit the R650.
Regulated workloads where silicon age is part of the audit. Several GCC banking clients have written “no Xeon Gen 1/2 in new deploys” into standards.

ICD compatibility catalogue

Both platforms share a large parts overlap in memory (via downclock) and 2.5″ SAS/SATA drives (same electrical, different caddy latch). CPU, motherboard, PSU, and PERC are platform-specific.

ICD supplies 14G and 15G spare parts from Cairo. For an R640 memory/RAID/PSU refresh or a full R650 build quote, open an RFQ. Ready-to-ship items reach Greater Cairo same-day and the rest of Egypt in 1–2 days, Morocco in 2–4 days, the UAE and Saudi Arabia in 3–4 days and Nigeria in 5–7 days.

Frequently Asked Questions

Will 2933 MHz RDIMMs from an R640 work in an R650?

Yes, they will train on the R650, but at 2933 speed if mixed with 3200 sticks. For a greenfield R650 build, a pure 3200 MHz population is the right spec, using numbers such as 6VDNY, 74FPM or 75X1V. The R650 also adds slots, taking up to 8TB (LRDIMM) across 32 DIMMs versus 3TB across 24 on the R640.

How do I know if my R640 fleet is already thermally limited?

Pull the BIOS fan-curve log from one R640 under 80% load. If fans stay above 50% PWM, you are already thermal-limited. The R640 chassis is rated to 205W TDP CPUs, while the R650 carries a 270W TDP ceiling, which is needed for a Platinum 8368.

How many NVMe drives can each of these 1U servers run?

The R640 offered up to 8 NVMe bays out of 10 in the universal chassis, or all 10 in the all-NVMe chassis, attached directly to the CPUs rather than through the PERC H740P. The R650 runs all 10 bays as NVMe direct-attach with the full-NVMe backplane, and offers PERC H755N NVMe RAID on its 8-bay backplane.

Which pass-through card replaces the HBA330 for vSAN or Ceph on the R650?

The HBA355i has replaced the HBA330 as the default pass-through card for software-defined storage, Ceph and vSAN on the R650. It belongs to the PERC 11 family, alongside the H345, H355, H755 and H755N, which add tri-mode SAS, SATA and NVMe support.