HP 591898-B21 Xeon X5660 2.8GHz Processor Upgrade

Name: HP 591898-B21 Xeon X5660 2.8GHz Processor Upgrade
Brand: HP
SKU: 591898-B21

HP Xeon X5660 processor upgrade brings six cores at 2.8GHz and 12MB cache to LGA 1366 servers.

$150.00*

*Price sourced from Amazon.com. Last updated:Jun 04, 2026.Price and availability are subject to change.

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Overview

The HP 591898-B21 is a processor upgrade kit featuring the Intel Xeon X5660, a hexa-core CPU based on Intel's 32nm Westmere-EP architecture. Running at 2.8GHz with 12MB of shared L3 cache and Hyper-Threading support, the X5660 provides 12 processing threads — a substantial upgrade for LGA 1366 servers that may currently be running dual-core or quad-core Xeon processors. This HP-branded kit is designed for validated compatibility with ProLiant server systems, reducing the risk of firmware or BIOS issues during installation.

The X5660 fits into Socket 1366 and was a popular choice in its generation for virtualization hosts, database servers, and compute-intensive workloads. While the Westmere architecture has been surpassed many times over by newer Intel generations, it remains functional for organizations that need to extract additional performance from existing LGA 1366 infrastructure without replacing the entire server. This particular unit is sold in used condition, so buyers should factor in the unknown prior usage when evaluating it for production workloads versus lab or development environments.

Specifications

Processor

Intel Xeon X5660

Cores / Threads

6 cores / 12 threads

Clock Speed

2.8 GHz

Socket

LGA 1366

L3 Cache

12 MB

Architecture

Westmere-EP (32nm)

Condition

Used

Brand

Model / Part Number

591898-B21

Pros & Cons

👍 Pros

Six cores with Hyper-Threading deliver 12 threads for strong multi-threaded server performance.
12MB L3 cache helps reduce memory latency for data-intensive workloads.
2.8GHz clock speed provides solid single-threaded performance for a server-class Xeon of this generation.
HP-branded kit simplifies installation with validated firmware and compatibility for ProLiant servers.

👎 Cons

Listed as used condition, so the processor's remaining lifespan and prior workload history are unknown.
LGA 1366 is a legacy platform with no current motherboard or chipset support from Intel.
The Westmere microarchitecture lacks modern features like AVX2 and newer instruction set extensions.
Power consumption is higher than equivalent-performance processors from more recent generations.

Frequently Asked Questions

What servers is this processor upgrade compatible with?

The HP 591898-B21 is a processor kit designed for HP ProLiant servers that use the LGA 1366 (Socket B) platform. Check HP's compatibility list for your specific server model before purchasing.

How many cores does the Xeon X5660 have?

The X5660 is a hexa-core (six-core) processor with Hyper-Threading, providing 12 threads for multi-threaded workloads.

What is the cache size on this processor?

It has 12MB of L3 cache (Intel Smart Cache) shared across all six cores.

Is this a new or used processor?

This item is listed as used/pre-owned condition.

What socket type does this processor require?

It uses Socket 1366 (LGA 1366), which is the standard socket for Intel's Westmere-EP Xeon 5600 series processors.