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Silver rectangular 3.5 inch bare hard drive with printed label

Western Digital

Western Digital WD6401AALS 640GB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" internal hard drive

SKU CH-J8M0-05125 MPN WD6401AALS

A 640 GB 3.5-inch desktop drive spinning at 7200 RPM with 32 MB cache and a SATA 3.0 Gb/s interface

  • Total capacity640 GB
  • Interface typeSATA 3.0Gb/s
  • Form factor3.5 in (8.89 cm)
  • Packaging typeBare Drive
  • Rotational speed7,200 RPM
  • Cache memory32 MB
  • 7200 RPM spindle speed accelerates data access
  • 32 MB cache buffer smooths burst transfers
  • SATA 3.0 Gb/s interface enables fast throughput
  • DoD 5220.22-M compliant erase sanitises the drive
  • 640 GB capacity stores ample desktop data

Capacity and interface

This Western Digital Caviar Black drive provides 640 GB of storage on a 3.5 inch form factor with a SATA 3.0 Gb/s interface. It spins at 7200 RPM and includes a 32 MB cache for desktop workloads. The unit is sold as a bare drive without cables or mounting hardware.

SATA 3.0 Gb/s practical limits

The SATA 3.0 Gb/s link caps theoretical throughput at 3.0 Gb/s, so sustained transfer rates will not exceed this ceiling. Native Command Queuing is supported to optimise command ordering on busy workloads. The drive is erased to DoD 5220.22 M standard and tested good, though up to 25 bad sectors may be present.

Pre-installation checks

Verify that your system has a free 3.5 inch drive bay and a spare SATA data and power connector. Confirm the BIOS or UEFI recognises SATA 3.0 Gb/s devices and that no drive-size limitation blocks a 640 GB volume. The drive ships unformatted and unpartitioned, so you must initialise it in the operating system before use.

How it compares

Measured against everything we stock in 3.5-Inch Internal Desktop HDDs, at today’s prices. Recalculated every night.

Price $75.99
Cheaper than about 61% of the 4,938 comparable items (median $107.99).
Total capacity 640 GB
Lower than about 74% of the 2,372 comparable items (median 2 TB).
Price per TB $118.73 per TB
Pricier than about 67% of the 2,365 comparable items (median $62.21 per TB).

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Specifications

Product
Brand nameWestern Digital
Product lineBlack
Model nameWD6401AALS
Total capacity640 GB
Performance
Rotational speed7,200 RPM
Storage
Cache memory32 MB
Ports & slots
Interface typeSATA 3.0Gb/s
Size & build
Form factor3.5 in (8.89 cm)
Shipping weight0.73 kg
Package size152 × 102 × 25 mm

Questions about this item

Should I choose the 640GB model or a different capacity?

This listing is for the 640GB version only. If you need more space, you would need to buy additional drives; if you need less, this drive still provides 640GB of storage.

What does the 7200 RPM speed mean for daily use?

The 7200 RPM spindle speed means the platters spin faster than slower drives, reducing the time the head waits for data to arrive and improving overall responsiveness when opening files or loading programs.

What does the SATA 3.0Gb/s interface limit in practice?

The SATA 3.0Gb/s link caps the maximum theoretical transfer rate at 3.0 Gb/s, so sustained read or write speeds cannot exceed that ceiling even if the drive's internal mechanics could go faster.

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