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Intel's Z68 Chipset and SSD Caching Reviewed


Last week, we noted that Apple's new iMac models utilize Intel's latest Z68 chipset, a component that Intel had yet to even publicly introduce at the time of the iMac's debut. The chipset has been highly anticipated for its ability to support SSD caching, a software technology that pairs a small solid state drive (SSD) with a conventional hard drive to significantly improve performance in a manner virtually invisible to the user.

While Apple's new Z68-based iMac does not currently support SSD caching, now officially known as Smart Response Technology (SRT), it actually goes further in offering the option of a secondary 240 GB SSD to directly host the user's operating system and applications, leaving the conventional hard drive for media and other data. But with reports just prior to the most recent MacBook Pro refresh in late February incorrectly claiming that the updated models would offer the option of a small secondary SSD to essentially perform SRT functionality, there has been significant interest in the possibility of Apple adopting Intel's solution.

With Intel's embargo on Z68 information having lifted earlier today, AnandTech has posted a thorough review of the chipset and the SSD caching feature. On a basic level, the report notes that Z68 is the chipset Intel should have launched for its Sandy Bridge platform earlier this year, overcoming a number of limitations related to overclocking and graphics options.

Intel's Z68 should have been the one and only high end launch chipset offered with Sandy Bridge. It enables all of the configurations we could possibly want with Sandy Bridge and does so without making any sacrifices. Users should be able to overclock their CPU and use integrated graphics if they'd like. While Z68 gives us pretty much exactly what we asked for, it is troubling that we even had to ask for it in the first place.

But the most anticipated feature of Z68 is its support for Intel's SRT SSD caching, and AnandTech takes a close look at the technology. With support currently available for Windows 7, it allows users to dedicate up to 64 GB of SSD space for caching purposes.

With Intel's RST 10.5 drivers and a spare SSD installed (from any manufacturer) you can choose to use up to 64GB of the SSD as a cache for all accesses to the hard drive. Any space above 64GB is left untouched for you to use as a separate drive letter.

Intel limited the maximum cache size to 64GB as it saw little benefit in internal tests to making the cache larger than that. Admittedly after a certain size you're better off just keeping your frequently used applications on the SSD itself and manually storing everything else on a hard drive.

That latter scenario is of course what Apple has chosen to do in the iMac with the secondary 256 GB SSD, although the company could certainly seek to utilize SRT on future systems as an alternative to the $600 price premium the larger SSD requires.

For its part, Intel has released a new "SSD 311" drive checking in at 20 GB and codenamed "Larson Creek". The SSD 311 is specifically designed as a caching SSD for Z68, utilizing high-performance and long-lasting single-level cell (SLC) flash memory and expected to be priced at around $110.

AnandTech goes on to explain the difference between the more secure "enhanced" and faster "maximized" modes for Intel's SSD caching and offers a number of benchmarks for booting and application launching. Overall, SSD caching offers much of the performance improvement of a full SSD solution, but at a fraction of the cost. Consistency is an issue, however, as the technology obviously requires that information be cached in the first place before speed enhancements can be seen. This limits speed improvements for application installation and first-time runs of applications, but frequently-used tasks quickly see significant speed increases.

Intel's Smart Response Technology (SRT) is an interesting addition to the mix. For starters, it's not going to make your high end SSD obsolete. You'll still get better overall performance by grabbing a large (80 - 160GB+) SSD, putting your OS + applications on it, and manually moving all of your large media files to a separate hard drive. What SRT does offer however is a stepping stone to a full blown SSD + HDD setup and a solution that doesn't require end user management. You don't get the same performance as a large dedicated SSD, but you can turn any hard drive into a much higher performing storage device. Paired with a 20GB SLC SSD cache, I could turn a 4-year-old 1TB hard drive into something that was 41% faster than a VelociRaptor.

It of course remains to be seen if Apple will even adopt SSD caching technology as an alternative to pricier standard SSD options, but the company's embracing of the Z68 chipset at least opens the door to the possibility at some point down the road.

Related roundup: iMac

Top Rated Comments

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44 months ago

Will this result in cheaper ssd prices now?


Not really but it will allow you to use small SSDs that might not be sufficient as a standalone drives. Basically, you can get SSD performance for less $ now.
Rating: 5 Votes
44 months ago

I like seagate's implementation better, where they actually put the ssd cache on the hard drive itself. Makes for a more compact arrangement. Don't know how the performance holds up, as seagate isn't currently offering as big of an ssd.


Seagate's option is easier for the end user but it lacks options. It is only available in 2.5" form factor and the maximum SSD size is 4GB. While it speeds up things a lot, 4GB isn't that much space so it can only hold a very limited amount of files.

I'm surprised that Seagate has not updated it and none of the other manufacturers have released something similar. I can see SRT being implemented in future laptops using mSATA SSDs. OEMs can set everything up in the factory so the end-user does not have to worry about hassling with it.

Could this be made to work in the new iMacs?

I assume software is also needed but I am sure someone will mess with it.


Theoretically yes. There is no word on official OS X support though so we may not see SRT in Macs in the near future.


$110 for only 20 GB? Holy crap!
I've thought this would be a great idea for a while now. but the price is still prohibitive for even the smallest SSDs. you can buy a 8 GB Flash Drive for like ten bucks, and a 16 GB one for like $25. Why not just put something like that directly on the motherboard for caching?

Edit: You can also get a 32Gb flash drive for just $50 so why $110 for the 20GB SSD? For that much you can get a 64 Gig flash drive It's the same tech


That 20GB uses SLC NANDs which are more expensive that the mainstream MLC NANDs. SSDs also need to use many NANDs to deliver good performance while flash drives can be a single NAND.

Nope. The MBPs use the HM65 chipset. You need a HM67 to get the feature as far as I know.


There is no mobile chipset that is comparable to Z68. ZM68 may come at some point but currently Z68 is the only one with SRT.
Rating: 4 Votes
44 months ago

$110 for only 20 GB? Holy crap!
I've thought this would be a great idea for a while now. but the price is still prohibitive for even the smallest SSDs. you can buy a 8 GB Flash Drive for like ten bucks, and a 16 GB one for like $25. Why not just put something like that directly on the motherboard for caching?


From what I understand the cheaper USB flash drives aren't as fast as the SSDs you would buy as a hard drive.

I would love for Apple to add the caching option in Lion. That would be a nice new feature to have. Currently I'm debating getting an SSD on my new iMac... it's tempting however, and this may tip the scales for me. :)
Rating: 3 Votes
44 months ago
$110 for only 20 GB? Holy crap!
I've thought this would be a great idea for a while now. but the price is still prohibitive for even the smallest SSDs. you can buy a 8 GB Flash Drive for like ten bucks, and a 16 GB one for like $25. Why not just put something like that directly on the motherboard for caching?

Edit: You can also get a 32Gb flash drive for just $50 so why $110 for the 20GB SSD? For that much you can get a 64 Gig flash drive It's the same tech
Rating: 2 Votes
44 months ago
I like seagate's implementation better, where they actually put the ssd cache on the hard drive itself. Makes for a more compact arrangement. Don't know how the performance holds up, as seagate isn't currently offering as big of an ssd.
Rating: 2 Votes
44 months ago

That is true, but $110 for a 20GB SSD is still expensive.

In several systems I use I've placed $80ish 64GB SSDs for the whole system drive. I dunno, I'd rather just have full out SSD performance for my system/apps/etc and not spend more money to start mixing SSD+HDD for less performance.


That's because the drives you've been using aren't Single Level Cell (SLC). They're the cheaper but less reliable Multi Level Cell or MLC. MLC drives have a limit of about 5000 erase/write cycles per block, whereas SLC is about 100,000. For a caching drive or one that will be written to frequently, SLC is important to prevent the drive dying prematurely. The problem with SLC, is it's extremely expensive for the same size drive.
Rating: 2 Votes
44 months ago

Some and arguably newer MBPs have a SATA III optical port


This is the big debate within the 2011 MBP community. Apple system profilier is showing SATA III for some and not for others. Do all the MBP have SATA III in the drive bay that would easily be activated through a firmware update, I hope so. With it being that fragmented I doubt Apple will enable SSD caching through OSX for the 2011 MBP's for this very reason. Might need to be hacked which could lead to other issues.
Rating: 2 Votes
44 months ago


I've got a late 2006 iMac that is fine for what I use it for, but the video card is failing at even warm temperatures and I am prone to Windows-like lockups lately. I was waiting for the 2011 refresh and hoping for the ridiculous performance boost that SSDs have provided MacBook Airs. Will No. 3 above provide it, or should I wait for Lion for more robust management of this?


Take your iMac apart and blow out all the dust, that'll help keep the GPU temperature down. Installing all your apps and OS on a SSD would be the best option. That way you can ensure exactly what you want to be fast (apps, iPhoto library, OS, etc) can be fast, but media like your iTunes library is kept off the SSD. I have an SSD in my 2006 Mac Pro, and it feels like a new machine.
Rating: 2 Votes
44 months ago

Intel offers two performance/integrity options. Best performance with deferred writes to hard disk, best integrity with write-thru. In this latter case, this might just work with a Thunderbolt connected SSD.


If the TBolt link is disconnected, the machine reboots, or probably even if it sleeps - it is probably necessary to flush the cache.

Reason being that any of the above could mean that either the SSD or the HDD could have been modified during the disconnect. That means that the cache could be out of synch - and the easiest method to resynch is to flush the cache and start over. This is similar to what happens if you pull a disk out of a RAID-5 array and reinsert - that disk has to be completely rewritten. (A hardware/software RAID-5 can tell if the disk was pulled while the array stayed off, and not resynch on every power cycle or reboot.)


Nothing like "must".
For example, if you use any kind of linked machines, clones, snapshots, or even sometimes sparse disk images, defragmenting can make things worse.


The standard method is to defragment the virtual disk from the guest, zero free space from the guest, then defragment the host image (folding any snapshot or linked images to a new base container file).

You're absolutely right that simply defragmenting on the guest alone can make an expandable disk image much worse. Two main reasons for this:[LIST=1]
[*]Even though from the guest the disk may appear very fragmented, on the host image there is temporal locality. As you're writing from the guest, the expanded segments are often close together. This can mean less physical head movement, although from the guest it looks like there would be a lot of head movement.
[*]The writes from the defragmenting may expand the disk further, and make the real disk more fragmented - and there's nothing to say that two adjacent clusters seen from the guest are on two adjacent cluster on the physical disk.
[/LIST]
Rating: 1 Votes
44 months ago

Not run out of space. A couple of gigs free space.

It's not a matter of raw space, but percentage.

You shouldn't let a drive fill up much past 80%, or it starts to impact the ability of the filesystem agorithms to efficiently place files. This is particularly true if you have a lot of write activity, even more so when dealing with large files.

If your drive is so full that only a few gigs are left, it is probably the cause of your thrashing (outside of doing something silly like running half a dozen VMs from a single spindle). Defragmenting - outside of corner cases - rarely makes any meaningful performance difference.
Rating: 1 Votes

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