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Many users have been finding themselves with brand new Sandy Bridge motherboards and the hard drive industry’s now affordable 3TB drives only to see that the new drive only has 746GB available in even 64-bit Windows. I receive questions about why this happens on Hitachi, Western Digital, Seagate, and Samsung drives on a regular basis so I think this is a fairly common issue. I myself fell victim to not following best-practice and seeing this issue manifest itself recently when I was benchmarking a new drive. As a result, I decided to make a guide so other users can easily fix the problem.


Test Configuration

For this guide I am using my standard hard drive test platform based on an Intel H67 motherboard. The operating system is installed on an SSD.

  1. CPU: Intel Core i5-2500K
  2. Motherboard: ASUS P8H67-M EVO
  3. Memory: 8GB 1600MHz CL9 DDR3 (4x2GB)
  4. OS Drive: ADATA S599 64GB SSD
  5. Hard Drive: Hitachi 5K3000 Coolspin 3TB
  6. Additional NICs: Intel Gigabit CT PCIe x1 network adapter
  7. Enclosure: Supermicro SC731i-300B
  8. Power Supply: Supermicro 300w (included in the SC731i-300B)
  9. Operating System: Windows 7 Professional 64-bit SP1
RST 2.8GB and Disk Management 746GB – 64-bit OS

The Problem

To test the problem I am going to use a Hitachi 5K3000 Coolspin 3TB hard drive with an Intel H67 motherboard’s onboard 6.0gbps controller in AHCI mode, alongside Windows 7 Professional SP1 64-bit. By the time a user is ready to upgrade to 3TB drives I would generally recommend that it is also a good opportunity to upgrade to a 64-bit version of Windows as hardware is starting to advance well beyond what the older Windows XP generation operating system can handle. One can easily spot the problem in the picture below:

Intel RST 2.8GB and Disk Management 746GB

Intel’s Rapid Storage Technology (Intel RST) console clearly identifies the Hitachi 3TB drive (showing 2.861TB above due to the way hard drive capacity is measured in industry marketing versus in operating system terms.) On the other hand, Windows Disk Management sees the disk (Disk 0 in the above) as a 746GB drive. That difference is the key to understanding how to fix the issue. The motherboard clearly sees a 3TB drive while the OS sees something that is excluding around 2.2TB of the raw capacity. Normally these types of issues can be traced to driver problems. I did a quick check of the Intel RST version that I had installed from the motherboard supplied driver disk showed:

RST 2.8GB and Disk Management 746GB – RST

The Intel RST version of it turns out is the culprit behind the 746GB available of the 3TB drive issue. For 3TB drive support, one should look to Intel RST 10.1 and newer.

RST 2.8GB and Disk Management 746GB – RST

The key here is downloading the newest version of Intel’s Rapid Storage Technology (Intel RST) drivers from Intel’s site. The download currently weighs in at around 6.5MB for the English only version making it a quick task to get on most broadband connections.

Intel RST 2.8TB ShownAfter installing Intel RST 10.1 or newer, that 746GB available turns into around 2.8TB, or in-line with what one would expect from a 3TB drive.


Overall, this is a very simple problem to fix, but one that I believe can be largely attributed to the fact that Windows 7 SP1 does not include Intel 82579 NICs found onboard in Cougar Point based chipsets. When a user does not have a network connection, the easiest thing to do is use the manufacturer’s installation media which often has older versions of things like Intel Rapid Storage Technology drivers. My main conclusion from seeing this issue crop up on multiple occasions is that one should ensure that they have downloaded the newest drivers for their system as soon as possible.



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