Intel Z68 Chipset & Smart Response Technology (SSD Caching) Reviewby Anand Lal Shimpi on May 11, 2011 2:34 AM EST
The problem with Sandy Bridge was simple: if you wanted to use Intel's integrated graphics, you had to buy a motherboard based on an H-series chipset. Unfortunately, Intel's H-series chipsets don't let you overclock the CPU or memory—only the integrated GPU. If you want to overclock the CPU and/or memory, you need a P-series chipset—which doesn't support Sandy Bridge's on-die GPU. Intel effectively forced overclockers to buy discrete GPUs from AMD or NVIDIA, even if they didn't need the added GPU power.
The situation got more complicated from there. Sandy Bridge's Quick Sync was one of the best features of the platform, however it was only available when you used the CPU's on-die GPU, which once again meant you needed an H-series chipset with no support for overclocking. You could either have Quick Sync or overclocking, but not both (at least initially).
Finally, Intel did very little to actually move chipsets forward with its 6-series Sandy Bridge platform. Native USB 3.0 support was out and won't be included until Ivy Bridge, we got a pair of 6Gbps SATA ports and PCIe 2.0 slots but not much else. I can't help but feel like Intel was purposefully very conservative with its chipset design. Despite all of that, the seemingly conservative chipset design was plagued by the single largest bug Intel has ever faced publicly.
As strong as the Sandy Bridge launch was, the 6-series chipset did little to help it.
Addressing the Problems: Z68
In our Sandy Bridge review I mentioned a chipset that would come out in Q2 that would solve most of Sandy Bridge's platform issues. A quick look at the calendar reveals that it's indeed the second quarter of the year, and a quick look at the photo below reveals the first motherboard to hit our labs based on Intel's new Z68 chipset:
Architecturally Intel's Z68 chipset is no different than the H67. It supports video output from any Sandy Bridge CPU and has the same number of USB, SATA and PCIe lanes. What the Z68 chipset adds however is full overclocking support for CPU, memory and integrated graphics giving you the choice to do pretty much anything you'd want.
Pricing should be similar to P67 with motherboards selling for a $5—$10 premium. Not all Z68 motherboards will come with video out, those that do may have an additional $5 premium on top of that in order to cover the licensing fees for Lucid's Virtu software that will likely be bundled with most if not all Z68 motherboards that have iGPU out. Lucid's software excluded, any price premium is a little ridiculous here given that the functionality offered by Z68 should've been there from the start. I'm hoping over time Intel will come to its senses but for now, Z68 will still be sold at a slight premium over P67.
Overclocking: It Works
Ian will have more on overclocking in his article on ASUS' first Z68 motherboard, but in short it works as expected. You can use Sandy Bridge's integrated graphics and still overclock your CPU. Of course the Sandy Bridge overclocking limits still apply—if you don't have a CPU that supports Turbo (e.g. Core i3 2100), your chip is entirely clock locked.
Ian found that overclocking behavior on Z68 was pretty similar to P67. You can obviously also overclock the on-die GPU on Z68 boards with video out.
The Quick Sync Problem
Back in February we previewed Lucid's Virtu software, which allows you to have a discrete GPU but still use Sandy Bridge's on-die GPU for Quick Sync, video decoding and basic 2D/3D acceleration.
Virtu works by intercepting the command stream directed at your GPU. Depending on the source of the commands, they are directed at either your discrete GPU (dGPU) or on-die GPU (iGPU).
There are two physical approaches to setting up Virtu. You can either connect your display to the iGPU or dGPU. If you do the former (i-mode), the iGPU handles all display duties and any rendering done on the dGPU has to be copied over to the iGPU's frame buffer before being output to your display. Note that you can run an application in a window that requires the dGPU while running another that uses the iGPU (e.g. Quick Sync).
As you can guess, there is some amount of overhead in the process, which we've measured to varying degrees. When it works well the overhead is typically limited to around 10%, however we've seen situations where a native dGPU setup is over 40% faster.
|Lucid Virtu i-mode Performance Comparison (1920 x 1200—Highest Quality Settings)|
|Metro 2033||Mafia II||World of Warcraft||Starcraft 2||DiRT 2|
|AMD Radeon HD 6970||35.2 fps||61.5 fps||81.3 fps||115.6 fps||137.7 fps|
|AMD Radeon HD 6970 (Virtu)||24.3 fps||58.7 fps||74.8 fps||116.6 fps||117.9 fps|
The dGPU doesn't completely turn off when it's not in use in this situation, however it will be in its lowest possible idle state.
The second approach (d-mode) requires that you connect your display directly to the dGPU. This is the preferred route for the absolute best 3D performance since there's no copying of frame buffers. The downside here is that you will likely have higher idle power as Sandy Bridge's on-die GPU is probably more power efficient under non-3D gaming loads than any high end discrete GPU.
With a display connected to the dGPU and with Virtu running you can still access Quick Sync. CrossFire and SLI are both supported in d-mode only.
As I mentioned before, Lucid determines where to send commands based on the source of the commands. In i-mode all commands go to the iGPU by default, and in d-mode everything goes to the dGPU. The only exceptions are if there are particular application profiles defined within the Virtu software that list exceptions. In i-mode that means a list of games/apps that should run on the dGPU, and in d-mode that is a smaller list of apps that use Quick Sync (as everything else should run on the dGPU).
Virtu works although there are still some random issues when running in i-mode. Your best bet to keep Quick Sync functionality and maintain the best overall 3D performance is to hook your display up to your dGPU and only use Sandy Bridge's GPU for transcoding. Ultimately I'd like to see Intel enable this functionality without the use of 3rd party software utilities.
Post Your CommentPlease log in or sign up to comment.
View All Comments
jordanclock - Wednesday, May 11, 2011 - linkYou can use a drive for both, but you must set up your data partition AFTER you set up the cache partition.
jorkolino - Wednesday, June 6, 2012 - linkWhat do you mean by that? You partition the SSD drive, install the OS in the first partition, set-up the other partition as a cache, and then format your remaining HDD?
jorkolino - Wednesday, June 6, 2012 - linkI wonder, can you tell SRT to cache blocks only from the HDD onto the cache partition, because by default SRT may decide to cache system files that already reside onto a fast SSD partition...
evilspoons - Wednesday, May 11, 2011 - linkI know it's early on for Z68, but I'm curious how other SSDs will perform in SRT mode. I ask because the 40 GB X25-V is on sale here for half its usual price...
evilspoons - Wednesday, May 11, 2011 - linkTo answer my own question, Tom's Hardware reviewed SRT with several SSDs and to put it bluntly, the X25-V sucks. Its very low write speed of 35 mb/sec actually drags the hard drive down in a few tests.
Shadowmaster625 - Wednesday, May 11, 2011 - linkYeah that is a nice way of putting it. Talk about sugar coating. Here is a question for ya: was intel being "conservative" when they tried to shove rambus down everyone's throats? If it werent for AMD and DDR god knows how much memory would cost now. I still have one of those rambus P4 systems running in the lab right now. (intel 850 chipset with dual channel RDRAM). I did some memory benchmarking on it and was shocked to find that it was actually slower than any of the P4 DDR 266 machines we have running. (Yes we are slow to upgrade lol.) It runs at about DDR200 equivalent speeds. And we really paid out the wazoo for that system.
Shinobisan - Wednesday, May 11, 2011 - linkdiscrete graphics cards are limited - even though they often have three, four.. or more connectors these days, they can often only drive two monitors at a time. (unless you use a displayport connector... and monitors with DP don't really exist yet)
I have two monitors driven by my HD6950 via the digital video out connectors. So the HDMI connector on that card is "dead" until I turn one of the monitors off.
What I would like to be able to do... is have my dGPU drive my two monitors, and the iGPU drive my 1080p TV via HDMI.
Can I do that? This discussion on virtu muddies the water some. unclear.
Conficio - Wednesday, May 11, 2011 - linkWell, so SRT is a good idea but again it is limited artificially in its use. Sounds to me like the P67/H67 stund all over again.
Why is it limited?
* For starters it is driver supported, and I believe that means Windows only (I could find no mention of what OS is supported). To be fully useful it belongs into the chipset/BIOS realm.
* Next there is the artificial 64GB limit. As is obvious from even the tests that is not really the practical limit of its usefulness. It is simply a marketing limit to not compete with Intels own full SSD business. You got to ask yourself, why not use your aging SSD of 100GB or 256 GB (a couple years down the road) as an SRT drive?
* "With the Z68 SATA controllers set to RAID (SRT won't work in AHCI or IDE modes) just install Windows 7 on your hard drive like you normally would." So only RAID setups are supported? Well you are testing with a single hard drive, so this might be a confusing statement. But if it is RAID only then that is ceratinly not what Joe Shmoe has in its desktop (let alone in its Laptop).
A5 - Wednesday, May 11, 2011 - linkIf the AT Heavy Workload Storage Bench is a typical usage case for you, than you shouldn't be using SRT anyway - you'd have a RAID array of SSDs to maximize your performance.
jordanclock - Wednesday, May 11, 2011 - linkFor caching purposes, I'm sure 64GB is a very reasonable limit. The more data you cache, the more data you have to pay attention to when it comes to kicking out old data.
And it isn't a RAID set up, per se. You set the motherboard to RAID, but the entire system is handled in software. So Joe Shmoe wouldn't even have to know what a RAID is, though I don't see Joe Shmoe even knowing what a SSD is...