Dell PowerEdge R750 Memory Upgrade Guide: Compatible DIMMs, Population Rules & Max RAM
The Dell PowerEdge R750 supports up to 4TB of DDR4-3200 RDIMM/LRDIMM across 32 DIMM slots. This guide covers every compatible memory part number, Intel Xeon Ice Lake population rules, and how to achieve full bandwidth without POST errors.
TL;DR — R750 Memory at a Glance
The Dell PowerEdge R750 is a 2U dual-socket server built on Intel Xeon Scalable 3rd Gen (Ice Lake-SP). It ships with 32 DIMM slots (16 per CPU), supports DDR4-3200 RDIMM and LRDIMM, and can reach a maximum of 4TB total RAM when fully populated with 128GB LRDIMMs. Most production deployments target 512GB–1TB.
Getting the memory configuration wrong — wrong rank, wrong slot order, mixing RDIMM and LRDIMM — will either result in reduced memory bandwidth or a failure to POST. Read the rules before ordering.
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Supported Memory Types
| Type | Max per DIMM | Max Capacity | Best For |
|---|---|---|---|
| DDR4-3200 RDIMM (1Rx8) | 16GB | 512GB | Cost-efficient builds |
| DDR4-3200 RDIMM (2Rx8) | 32GB | 1TB | General workloads |
| DDR4-3200 RDIMM (2Rx4) | 64GB | 2TB | Database, virtualization |
| DDR4-3200 LRDIMM (4Rx4) | 128GB | 4TB | In-memory databases, large VMs |
Do not mix RDIMM and LRDIMM in the same system. The memory controller treats them differently and will refuse to initialize.
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Compatible Dell Part Numbers
| Capacity | Type | Dell PN | Speed |
|---|---|---|---|
| 16GB | RDIMM 1Rx8 | AA799064 | DDR4-3200 |
| 32GB | RDIMM 2Rx8 | AA799065 | DDR4-3200 |
| 64GB | RDIMM 2Rx4 | AA799087 | DDR4-3200 |
| 128GB | LRDIMM 4Rx4 | AA799109 | DDR4-3200 |
| 256GB | LRDIMM 8Rx4 | AB128227 | DDR4-3200 |
Always verify the Dell part number against your R750 generation and BIOS version. Dell periodically releases BIOS updates that add support for newer DRAM revisions.
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DIMM Population Rules (Critical)
The R750 uses a 2-CPU, 8-channel-per-CPU memory architecture (8 channels × 2 DIMMs per channel per CPU = 16 slots per CPU, 32 total). To achieve maximum DDR4-3200 bandwidth, follow these rules:
Rule 1: Populate symmetrically across CPUs
If you install memory on CPU 1, install the same configuration on CPU 2. An asymmetric config degrades to the lesser side's speed.
Rule 2: Fill channels before doubling up
For a 2-DIMM-per-channel system, fill one DIMM per channel across all 8 channels on each CPU before adding the second DIMM to any channel. This means:
- 1 CPU: slots A1, B1, C1, D1, E1, F1, G1, H1 first (8 DIMMs at full DDR4-3200)
- Then add A2, B2, C2, D2, E2, F2, G2, H2 (16 DIMMs per CPU)
Rule 3: Minimum 2 DIMMs per CPU
The R750 requires at least one DIMM in slot A1 on each populated CPU socket. A system with CPU 2 installed but no memory on CPU 2 will POST with a warning and run in degraded mode.
Rule 4: Do not mix speeds
If you insert DDR4-2666 modules alongside DDR4-3200, the entire system downclock to 2666. Buy matching speed.
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Recommended Configurations by Workload
| Workload | DIMMs | Capacity | Config |
|---|---|---|---|
| Light virtualization (VMware Essentials) | 4×32GB | 128GB | 2 per CPU, 2 channels |
| Mid-tier vSphere (8–16 VMs) | 8×32GB | 256GB | 4 per CPU, 4 channels |
| Heavy virtualization / VDI | 16×32GB | 512GB | 8 per CPU, 8 channels |
| Large SQL Server / SAP HANA | 16×64GB | 1TB | 8 per CPU, full bandwidth |
| In-memory analytics | 32×128GB | 4TB | Full LRDIMM population |
For VMware vSphere environments, a minimum of 256GB is recommended to avoid memory ballooning on 16+ VMs. See our Server Virtualization Hardware Requirements guide for full per-hypervisor recommendations.
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How to Physically Install
- Power down the R750 and remove the power cables (or use iDRAC to graceful shutdown).
- Remove the top cover (single thumb-screw on most R750 models).
- Locate the DIMM slots — they are labeled A1–H2 on CPU 1 side and A3–H4 on CPU 2 side (left to right when facing the board).
- Press the ejector tabs outward on the empty slot.
- Align the DIMM notch to the slot key — DDR4 has a single off-center notch.
- Press firmly and evenly until both ejector clips click into place. Do not force.
- Reassemble and power on. iDRAC will enumerate the new memory on first boot.
- Verify in iDRAC > System > Memory or with
dmidecode -t 17(Linux) that all modules are recognized at DDR4-3200.
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Troubleshooting Memory POST Errors
Memory uncorrectable error at POST: Usually a bad or incompatible DIMM. Reseat the suspect module first. If the error follows the DIMM to a new slot, replace the module.
Memory running at DDR4-2666 instead of 3200: Mixed-speed modules in the same channel, or a 2-DIMM-per-channel config that forces a speed reduction. Check the Dell population chart — some 2-DIMM-per-channel configs are limited to 2933 or 2666 depending on rank.
System sees less RAM than installed: One or more DIMMs not seated fully, or a failed DIMM. Check iDRAC for the specific slot reporting the error.
POST warning about memory configuration: Asymmetric population (different quantities on each CPU). Not a failure, but not optimal — balance both sides.
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Buying Refurbished R750 Memory
The R750 uses standard DDR4-3200 RDIMM/LRDIMM with no proprietary HPE-style lock-in — any server-grade DDR4-3200 ECC module with the correct rank and form factor will work. Refurbished Dell-pulled DIMMs offer 30–50% savings with no performance difference. Memory has no moving parts and degrades only from ECC-reported errors (which are logged in iDRAC).
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Pro Disk Network stocks Dell PowerEdge R750 compatible memory — DDR4-3200 RDIMM and LRDIMM in 16GB through 256GB capacities — with same-day US shipping and Net 30 for verified businesses. Tell us your target capacity and workload and we will spec a balanced, full-bandwidth configuration. Browse server memory or contact us for a quote.
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