3TB Internal Drive as 746GB

I’ve searched the forums and seen some posts about people with 3tb drives only being recognized as 2.2tb, but my case is a bit different.  I have an internal Caviar Green drive that’s 3tb and mounted in an external USB enclosure and is only being seen by Windows as 746.39gb.  Does anyone know how I can get the full drive recognized?

I have a Gigabyte P55-UD4P Rev1 board and have Windows 7 64bit installed.  I have the latest chipset drivers and the latest BIOS for this board installed.  I’ve also repartitioned the volume as GPT, but Windows still sees it as only 746gb.


What are you using to format it just Windows? You might try a third party format tool and see if that works. I’ve searched but can’t find the post but when this came up a while ago the problem was the drive in the third party enclosure. I think they had to connect as an internal and format it then put it in the enclosure. If I can find the post I’ll add the link. It may have been in the external drive section. I think it was in the last 2 weeks.


This could be an indication that the enclosure does not support drives larger than 2 TB.  If your motherboard supports a 3 TB drive you may try installing the drive on it to compare results.

AIUI, the firmware in most older external enclosures is limited to 32-bit LBAs. This means that the maximum addressable capacity is 2TiB, which corresponds to a maximum LBA of 0xFFFFFFFF.

The USB-SATA bridge chip in the enclosure retrieves the drive’s capacity by issuing an ATA Identify Device command. The drive responds with a 512-byte data block which includes its model number, serial number, and capacity. The total number of LBAs is stored by the drive as a 48-bit value. However, because the bridge firmware is limited to 32-bits, the bridge IC reports only the lower 32 bits of the capacity to the host PC.

For example, the WD30EZRS has a capacity of 5860533168 LBAs. The hexadecimal value is 0x15D50A3B0.

If we take the lower 32 bits and discard the uppermost bits, then this number reduces to 0x5D50A3B0.

At 512-bytes per LBA, the reported capacity is now only 801GB:

This is equivalent to 746.5 GiB:

Depending on the chip in the enclosure, you may be able to upgrade its firmware so that it supports the full 3TB. Can you tell us the markings on the largest chip on the bridge PCB?

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Thanks for all the posts, I didn’t think of the enclosure as being the bottleneck.  I’ll mount the drive internally and see what the result is.  However if the enclosure was limiting it, why would it show up as 746gb instead of 2.2tb?

Also, Joe_S, I formatted it to GPT using the Windows diskpart command line utility.

I’m not sure how best to explain it another way.

However, let’s assume that the drive has 5100 sectors, and that the enclosure’s USB-SATA bridge IC communicates using decimal numbers. Assume also that the bridge can only handle 3 decimal digits. This means that it will report a capacity of 100 sectors rather than 5100.

If the OS asks for any sector in the range 0 - 999, then the bridge will quite happily fetch the correct one. However, if the OS asks for sector 1000 or 2000 or 3000 or even 9000, then the bridge will probably return the data in sector 000.

I could be wrong, but that seems to be what is happening.

It was the enclosure.  Thanks for all the replies guys.  Time to go look for an enclosure with a 64 bit controller.

You don’t need a 64-bit bridge CPU, you just need a 32-bit CPU (or less) that understands 48-bit LBAs.

That said, if your bridge IC has a firmware update, then that may be all you need.

For example, the following chip is a common one:


Here is a thread where the OP has resolved a 3TB recognition problem in his USB enclosure:

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Thanks for the info.  I’ll check it out and see if I can find one for my enclosure.  I threw away the packing materials and box, so I’ll see what I can find.

Oh dear had I known there was an issue with the 3.TB drives and bios maybe I would not of purchase, as it is I have two internal: Dell WD30EZRX Western Digital 3.TB 7200PM Sata hard drives which at first formatted similar to yours. I have now managed to format them as below, 1.TB short.

        Drive: F:

 Free Space: 2097.0 GB

Total Space: 2097.1 GB

File System: NTFS

      Model: WDC WD30EZRX-00MMMB0 ATA Device

      Drive: G:

 Free Space: 2097.0 GB

Total Space: 2097.1 GB

File System: NTFS

      Model: WDC WD30EZRX-00MMMB0 ATA Device

After reading through your topic and noting what’s bean said, it would seem I have to update my old Asus P5QC Motherboard bios, it will flash and I understand there is an ASUS update utility that can be used within the windows environment. I will post here again to let anyone that maybe interested how I get on.

I decided to post here rather than start a new topic because the issues are the same, I hope you don’t mind.

From Dieapy.

dieapy, have you updated your SATA drivers to the latest versions?

If your board has two SATA controllers, try the non-Intel controller.

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Ok all my problem with the 3.TB WD drive not formatting to it full prudential is solved, it was so easy it was unbelievable all one has to do is convert the Master boot record (MBR) into a GUID partition table (GPT) then format the partition job done.

Use link for tech guide


from dieapy

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