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Are USB or FireWire hard drives affected by Operating System and BIOS capacity limitations?

July 1st, 2010

USB and FireWire hard drives are not affected by motherboard BIOS capacity limitations.

USB/FireWire Hard Drives The FireWire 1394a, 1394b, USB 1.1, and USB 2.0 protocols natively support 48-Bit LBA (Logical Block Addressing). The 48-Bit LBA standard is for addressing support of hard drives larger than 137GB. There may be an Operating System limitation related to drives over 137GB.

  • All Mac Operating Systems later than 9.0 support 48-Bit LBA natively.
  • For Windows 2000, Service Pack 3 (or later) must be installed to add 48-Bit LBA support to Windows.
  • For Windows XP, Service Pack 1 (or later) must be installed to add 48-Bit LBA support for Windows.
  • These Operating System updates can be downloaded from Microsoft’s Website.

It is important to note that the reported capacity of a large drive may often appear as less than expected. Please remember that, depending on the particular utility used, the capacity of the hard drive can be reported in either decimal gigabytes (where 1 GB = 1,000,000,000 bytes) or in binary gigabytes (where 1 GB = 1,073,741,824 bytes). Highlighting your C: drive in Windows Explorer reports the drive capacity in binary gigabytes. For example, a WD2000BB hard drive’s capacity will be reported as approximately 186 binary gigabytes.

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