Dell PowerEdge R740: The Balanced 2U

The PowerEdge R740 is the 2U member of Dell's 14th generation, and it shares nearly everything with the 1U R640: two LGA 3647 sockets, 24 DDR4 DIMM slots, the same PERC controllers, the same BOSS boot card, the same iDRAC9 management stack. What the second rack unit buys is expansion slots, drive bays, cooling headroom, and the ability to carry double-width accelerators. That is the entire decision.

What the extra rack unit actually gives you

Expansion is the headline difference. Depending on the riser configuration installed, the R740 provides anywhere from three to eight PCIe 3.0 slots, up to three of which are x16, and it accepts full-height cards rather than low-profile only. That is the difference between one HBA plus one NIC and a machine that can host a SAS HBA, dual 25GbE, a Fibre Channel pair, and still have room left.

The chassis also supports up to three 300 W double-width GPUs or up to six single-width accelerators, though that configuration is not a casual add-on: it requires the GPU-enabled riser configuration, high-performance heatsinks, the right fan complement, and higher-output power supplies. If a listing does not mention GPU enablement, assume the parts are not there.

The less obvious benefit is thermal. Six hot-plug fans and a taller heatsink envelope mean 165 W and 205 W processors run with more margin and considerably less fan noise than the same parts crammed into 1U. For a server that lives near people, or in a room with marginal cooling, that matters.

Drive layouts

Front storage is set by the chassis and backplane that were built in, not by a configuration option you can add later.

Front layout	Bays	Typical fit
8 x 3.5" SAS/SATA	8	Capacity tiers, backup targets, archive and media stores
8 x 2.5" SAS/SATA	8	Moderate VM hosts where PCIe slots matter more than spindle count
16 x 2.5" SAS/SATA	16	VM density, mixed SSD and HDD tiers, software-defined storage nodes
16 x 2.5" with NVMe-capable bays	16, a subset wired for NVMe	Latency-sensitive databases, cache or write tiers in front of bulk storage

Two things to keep straight here. First, NVMe bays connect to CPU PCIe lanes through extender cards rather than through the PERC, so there is no hardware RAID across NVMe on this generation; redundancy comes from ZFS, mdraid, Storage Spaces, vSAN, or your hypervisor of choice. Second, the R740 and the R740xd are different chassis, not different option packages. If you need 24 x 2.5-inch bays, 12 x 3.5-inch bays, or rear-mounted drives, that is R740xd territory and you cannot convert an R740 into one by swapping a backplane.

For boot devices, the BOSS-S1 card holds two M.2 SATA modules in RAID 1 on an internal riser, which keeps the hypervisor off the front bays and out of your data array. Controller options are the usual 14th-generation set: HBA330 for pass-through, H730P or H740P when you want cache-backed hardware RAID.

Risers, the second CPU, and slot mapping

Slot count on an R740 is a function of which riser configuration is installed and whether both sockets are populated. Several slots are wired to CPU2 and are simply inactive in a single-processor build, which is the most common surprise when someone buys a single-CPU system and then cannot find the x16 slot they planned around. Before committing to a card layout, confirm the riser configuration and the processor count together.

The same logic applies to NVMe bays and to some networking options: lanes come from the CPUs, and a second CPU means more lanes to distribute.

Memory and processors

Both sockets take first-generation (Skylake-SP) and second-generation (Cascade Lake) Xeon Scalable processors up to 28 cores and 205 W. Memory is six channels per socket, two DIMMs per channel, 24 slots in total, reaching 3 TB with 128 GB LRDIMMs. That ceiling comes with a condition: twelve 128 GB modules is 1.5 TB per socket, more than the 768 GB per socket standard first-generation parts address and more than the 1 TB per socket standard second-generation parts address, so 3 TB requires M-suffix processors. Populate in multiples of six per CPU; twelve identical DIMMs across two sockets is the balanced baseline. First-generation parts run at up to 2,666 MT/s, second-generation parts at 2,933 MT/s with one DIMM per channel, falling back to 2,666 once the second DIMM per channel is filled. A system on older firmware needs a BIOS update before it will POST with second-generation processors.

Practical notes before you order

• iDRAC licensing. Virtual console and virtual media require iDRAC9 Enterprise. Check the license tier before planning a remote install.
• Power supplies. Redundant pairs should match wattage; mixing different-wattage supplies is not a supported configuration. The range runs from 495 W to 2,400 W, with 750 W, 1,100 W and 1,600 W units the ones you see most often; GPU-loaded builds need the higher-output end of that range.
• Rails and depth. A 2U chassis with a cable management arm needs real rack depth. Measure before it arrives, not after.
• Fan and heatsink kits. Processors above 150 W and GPU configurations require the high-performance heatsink and specific fan types. These are chassis-level parts, so it is easier to buy the right build than to retrofit one.

Where to go from here

Look through the available Dell PowerEdge R740 systems to see which drive layouts, riser configurations, and processor pairs are on hand. If rack units are tighter than slots in your environment, the 1U R640 runs the same processors and memory. When you have a target configuration in mind, build it on Build Your Server and send it in as a quote request; we will validate the riser, backplane, and power combination before quoting it.