Are USB hard drive sizes limited by motherboard hard drive controller?

Are USB hard drive sizes limited by motherboard hard drive controller?

I'm looking to put an expansion EIDE controller in my dad's desktop so it can handle a new 500 GB drive (evidently the motherboard EIDE controller has the 137 GB limit). He got a 500 GB USB hard drive for it, too, and I was wondering if that would work with the computer (with the new controller card in). Maybe I'm thinking about it wrong, I don't know, but it doesn't hurt to ask. Also, if it would work, would it be because of the new controller card, or not?

Asked by: Guest | Views: 226

Total answers/comments: 1

Comments display order:

Guest [Entry]

"Are USB hard drive sizes limited by motherboard controller? Which controller do you mean?

If you're talking about the motherboard's hard drive controller (IDE/SATA), no.

If you're talking about the motherboard's USB controller, yes no.

USB's USB Mass Storage protocol is what governs USB storage. The protocol uses ATAPI (ATA Packet Interface) commands to access the drive. The ATAPI support is provided by a USB-to-ATAPI bridge chip in the external drive.

The USB-to-ATAPI bridge chip, and your OS, both need to support 48-bit addressing to get large-drive (>137GB) support. That's Win2000 SP3+, WinXP SP2+, and any versions of Vista and Win7.

The USB-to-ATAPI bridge chip is what might not support a large drive. If that chip uses the old 28-bit addressing (for the IDE backend), you'll hit the 137GB size limit. This is only a concern if you're buying an old USB enclosure and putting a new large drive inside it -- any prebuilt external drive will use a bridge chip appropriate to the size of the drive.

BIOS support for USB Mass Storage is only necessary for booting from a USB drive. I can't find any details, but even if your BIOS only supported 28-bit addressing, you could probably still boot from a partition in the first 137GB of the drive; once the OS is loaded, the BIOS limitations are irrelevant."