It’s Been a Long Time Coming
It was way back in September, when we first heard about Seagate’s latest top-end enthusiast hard drive. The Barracuda XT was meant to supplant the 7200.12, adding several never-before-seen features. Four months later, it’s finally available in stores, at about $300 each for the 2TB drive.
Why it was delayed, I’m not sure. It is after all using the latest SATA 3.0 control chip, and maybe that caused issues. Actually, we’re not supposed to call it that, due to potential confusion with an already confusing SATA naming scheme. But it is the third revision of SATA, so I’ll call it SATA 3.0. Or SATA 6 Gbps (though as you’ll see later, it hardly deserves that title).
In any case, it’s here, and we have put it to the test. First, let’s talk about what makes it so special. First, here’s a quick look at the specs:
|Barracuda XT||Barracuda 7200.12|
|Platter Size||500 GB||500 GB|
|Available Capacities||2 TB Only||Up to 1 TB|
|Max. External Transfer Rate||600 MB/s||300 MB/s|
|Max. Internal Transfer Rate||136 MB/s||125 MB/s|
|Cache Size||64 MB||32 MB (on 1 TB ver.)|
|Spindle Speed||7200 RPM||7200 RPM|
|Avg. Rotational Latency||4.2 ms||4.17 ms|
|Read Seek Time||<8.5 ms||<8.5 ms|
|Write Seek Time||<9.5 ms||<9.5 ms|
|Areal Density||347 GB/inch2||329 GB/inch2|
|Idle Acoustics||2.8 bels||2.5 bels|
|Seek Acoustics||3.2 bels||2.7 bels|
|Warranty||5 Years||3 Years|
|Price||$300 (2 TB)||$100 (1 TB)|
As you can see, very little separates the XT from the 7200.12. They share the same platters – there’s just four of them instead of two. And despite the fact that the XT uses a next-generation SATA 3.0 controller with an external data transfer rate of 600 MB/s, the internal transfer rate of the drive is barely faster than the 7200.12, at 136 MB/s. It does have double the cache though, which potentially will benefit from the higher external transfer rate. And you do get an extra 2 years on your warranty, since Seagate arbitrarily shortened the warranty on their ‘mainstream’ Barracuda drives to 3 years. So is it worth spending $300 on a single 2 TB drive, when you could get a pair of 1 TB drives for $200? Read on to find out…
You’ll Need One Of These
Of course to get full SATA 3.0 connectivity, you will need a SATA 3.0 controller. Currently these are not found on motherboard chipsets from Intel or AMD. If a motherboard manufacturer wants to support SATA 3.0, an auxiliary controller chip is required. As is often the case, they turn to Marvell for a solution. Marvell’s SE9128 is the chip Gigabyte went to on their P55 motherboard (which we will have a full review of soon).
The two-channel RAID-capable SE9128 sits on a single PCI-E Gen2 bus lane, which gives it 500 MB/s worth of bandwidth. Yes, that is a full 100 MB/s less than the SATA 3.0 spec allows, and if you are using a pair of these drives in RAID, you are choking it even more (in theory). But that’s not where the roadblocks end.
As you may be aware, however, the P55 PCH does not fully support Gen2 speeds – they max out at 250 GB/s. There are two solutions to this: Add an auxiliary PCI-E 2.0 switch, or use the full Gen2 lanes that reside on the CPU’s PCI-E controller. Asus opted for the former on their boards, but Gigabyte’s solution was a bit different.
If you enable full SATA 3.0 speed on your Gigabyte P55 motherboard, it takes up one of the 16 lanes coming from the CPU. This has the effect of taking up 8 full lanes, since that is how it must be split. The remaining 8 lanes go to the main PCI-E graphics slot, and the second graphics slot is disabled. This is what allows Gigabyte to add SATA 3.0 and USB3 to their entire P55 lineup, where Asus’ more expensive route requires them to only support it on their most expensive boards.
That’s right, if you want to use SATA 3.0 (or USB 3) at full speed on your Gigabyte board, you can forget about running a dual graphics card setup. And although your single card will also be cut to 8x worth of PCI-E bandwidth, that is plenty. You can still run these controllers from the single 250 MB/s lane on the PCH, but you will be adding another bottle neck. Just disable “Turbo USB” and “Turbo SATA” in the BIOS.
Of course, the Barracuda XT already has a huge 136 MB/s bottleneck as it is, since it is a mechanical drive. Speaking of which, let’s take a look at the performance of this drive.