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Why are these hard drive enclosures advertised as having 160 GB maximum capacity?

http://amazon.co.uk/dp/B008MRBMPA

USB 2.0 interface (Compatible with USB 1.1), Up to 480 Mbps data transfer rates, 160GB capacity max

http://amazon.co.uk/dp/B0047YUUN2

brand new 2.5 inch External Hard Disk Drive Enclosure Case,Support all 2.5 inch (9.5mm) (max. capacity 160 GB) High IDE Notebook Nard Disk Drive, and It makes high-speed data transfers----supports USB 2.0 up to 480Mbit/sec, USB 1.1 up to 12Mbit/sec;

http://amazon.co.uk/dp/B00AVXMFIG

Maximum hard disk capacity: 160 GB

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  • Its the usb chip in the enclosure that limits drive size not the advertised specs. – Moab Jan 13 '16 at 15:00
  • Because of the controller chip. As manufactures produce products with more storage capacity they also have to go to their chip vendors to update the controllers for those devices. As for the reason for that capactiy limit, they are IDE drives, 160GB was near the maximum capacity IDE drives got to before SATA I came out. They are also $3, in other works, they are complete rubbish. – Ramhound Jan 13 '16 at 18:06
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The way most vendors work, they do not re-qualify out-of-production hardware for the latest specifications (unless some huge purchase contract relies on it, anyway), so as long as these old models stay in stock, their specs say the same. They may or may not support more modern, higher density hard drives, but vendors and the manufacturer won't guarantee it.

But why 160GB? It's not a common PC BIOS or CHS->LBA limitation, the closest would be 128GB. Back in 2007, 9.5mm drives went to 160GB while 200GB+ you had to buy a 12.5mm drive. That was just the state of the industry at that moment. You can see discussion in Mac forums like this: http://ask.metafilter.com/63097/Whats-the-max-size-harddrive-I-can-put-in-a-MacBook

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  • 160 GB was 2 platters with 40 GB to each side. 200 GB used 3 platters with 1 side of the 3rd being unused. That's why the height increased to make room for the extra platter. (I have seen some 200GB drives that were actually 240 (all 6 sides) with a software-limit. You could make them 240 GB by flashing the firmware with a copy of the real 240 GB model.) – Tonny Jan 13 '16 at 14:50
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    continued Very well possible that the 160 in this case is determined by the physical dimensions of the most common drives of the time. – Tonny Jan 13 '16 at 14:50
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Modern enclosures (SATA) typically can handle drives up to 2 TB using 512 byte block-sizes and some enclosures support even larger disks with 4K block-sizes.
Older ones, for IDE-drives, usually have a 512 GB upper limit.
The ones you linked to are quite ancient IDE drive enclosures.

2 reasons come to mind for a 160 GB limit:

1) There is a USB to SATA (or IDE) converter-chip inside the enclosure that connects the harddrive itself to the USB. These sometimes have a maximum supported drive-size. (Although 160 GB is a bit strange. The limit is usually 512 GB (for IDE-drives) or 2 TB (for SATA-drives), because that is a natural boundary.)

2) They only tested up to a certain size (whatever was available at the time the chip was designed) and put that as limit on the packaging. It may work with bigger drives, but that is untested, so they put the tested limit on the box to prevent product-liability claims.

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  • IIRC there was also a problem with SATA drives around that size. Something to do with bits used to count addresses in a driver. That was win2000 era, but if you have en enclosure with a chipset from that time and the same basic driver structure.... (for more info google on 4 or 48bit LBA). – Hennes Jan 13 '16 at 14:22
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    @Hennis Without LBA48 (Ie. Windows 2000 before SP3 or older BIOSses that didn't support it) you could only do CHS addressing which was limited to 128GB (counting in 1024 byte units) or 137 GB (if you count in 1000 byte units). Not 160 GB. That isn't a natural boundary no matter how you look at it. – Tonny Jan 13 '16 at 14:44
  • Ok. it was a long time ago. I remember it was in that range because we hit it with our shiny new windows 2000 backup server. But yes. Ages ago. – Hennes Jan 13 '16 at 15:18
  • @hennes We're getting old my friend :-). I started out on CP/M and Dos V2 in the early 80's. – Tonny Jan 13 '16 at 20:43

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