The 2013 MacBook Air Review (13-inch)
by Anand Lal Shimpi on June 24, 2013 12:01 AM ESTA Custom Form Factor PCIe SSD
In the old days, increasing maximum bandwidth supported by your PATA/SATA interface was always ceremonial at first. Hard drives were rarely quick enough to need more than they were given to begin with, and only after generations of platter density increases would you see transfer rate barriers broken. Then came SSDs.
Not only do solid state drives offer amazingly low access latency, but you can hit amazingly high bandwidth figures by striping accesses across multiple NAND Flash die. A 256GB SSD can be made up of 32 independent NAND die, clustered into 8 discrete packages. A good controller will be able to have reads/writes in flight to over half of those die in parallel. The result is a setup that can quickly exceed the maximum bandwidth that SATA can offer. Today that number is roughly 500MB/s for 6Gbps SATA, which even value consumer SSDs are able to hit without trying too hard. Rather than wait for another rev of the SATA spec, SSD controller makers started eyeing native PCIe based controllers as an alternative.
You can view a traditional SSD controller as having two sides: one that talks to the array of NAND flash, and one that talks to the host system’s SATA controller. The SATA side has been limiting max sequential transfers for a while now at roughly 550MB/s. The SATA interface will talk to the host’s SATA interface, which inevitably sits on a PCIe bus. You can remove the middle man by sticking a native PCIe controller on the SSD controller. With SATA out of the way, you can now easily scale bandwidth by simply adding PCIe lanes. The first generation of consumer PCIe SSDs will use PCIe 2.0, since that’s what’s abundant/inexpensive and power efficient on modern platforms. Each PCIe lane is good for 500MB/s, bidirectional (1GB/s total). Apple’s implementation uses two PCIe 2.0 lanes, for a total of 1GB/s of bandwidth in each direction (2GB/s aggregate).
The move to a PCIe 2.0 x2 interface completely eliminates the host side bottleneck. As I pointed out in my initial look at the new MacBook Air, my review sample’s 256GB SSD had no problems delivering almost 800MB/s in peak sequential reads/writes. Do keep in mind that you’ll likely see slower results on the 128GB drive.
Users have spotted both Samsung and SanDisk based PCIe SSDs in the 2013 MacBook Airs. Thankfully Apple doesn’t occlude the controller maker too much in its drive names. An SM prefix denotes Samsung:
My review sample featured a Samsung controller. There’s very little I know about the new Samsung controller, other than it is a native PCIe solution that still leverages AHCI (this isn't NVMe). Within days of Apple launching the new MBAs, Samsung announced its first consumer PCIe SSD controller: the XP941. I can only assume the XP941 is at least somewhat related to what’s in the new MBA.
The Samsung controller is paired with a 512MB DDR3 DRAM and 8 Samsung 10nm-class (10nm - 20nm process node) MLC NAND devices.
New PCIe SSD (top) vs. 2012 MBA SATA SSD (bottom) - Courtesy iFixit
Despite moving to PCIe, Apple continues to use its own proprietary form factor and interface for the SSD. This isn’t an M.2 drive. The M.2 spec wasn’t far enough along in time for Apple to use it this generation unfortunately. The overall drive is smaller than the previous design, partially enabled by Samsung’s smaller NAND packages.
Facebook
Twitter
RSS
233 Comments
View All Comments
doobydoo - Tuesday, June 25, 2013 - link
Sigh @ Ignorant people who compare processors of different architectures by GHz.TheinsanegamerN - Sunday, June 30, 2013 - link
the boost clocks are similar, and the haswell boosts way more than ivy bridge did. look at the cpu scores, which are similar, despite the 400 mhz reduction.Krysto - Monday, June 24, 2013 - link
Disappointing to see that even Apple has started being misleading about its battery life for laptops.It seems unlike Steve Jobs, Tim Cook is more of a "regular manager" who prefer spec lists and bullet points, over being truthful to customers. Now they're just lying about battery life numbers just as every other PC OEM out there - 12h of battery life! (but you might actually get only half of that).
And all that with a CPU that is 20 percent slower than last year, and a GPU that's twice as big but only 10-20 percent better than last year.
Also, the dual core Haswell chip alone costs $350? Yikes. So you still think these chips have any chance of competing in the tablet space, Anand? The whole of iPad Mini costs less than that, with a sub $30 chip. Intel is as behind as always when it comes to competing in the mobile space.
madmilk - Monday, June 24, 2013 - link
Sheesh, at least read the review. The battery life is 11 hours on the light workload, which is certainly more than half of the advertised 12. This difference is easily accounted for by the higher screen brightness and Flash. The 1.3GHz Haswell is not 20% slower either than the comparable 1.7GHz Ivy. More like 5% at worst, and in several cases faster. The GPU is 20% faster in a _much_ lower TDP, once the FIVR and PCH are accounted for, which contributes to the very impressive battery life on the heavy workload as well. As for Haswell pricing -- ULV i5/i7 are in another league compared to any ARM offering on the market. Atoms and Celerons are more appropriate for the toy tablet market.Sushisamurai - Tuesday, June 25, 2013 - link
... If you read the fine print on apple's website, they increased the benchmark demands on the MBA compared to previous battery tests just to make the 12 hrs seem more realistic. CNET and a few other sites posted their battery tests of the 13" to be rated for 14+ hours. I think anand already made a point about this...And if you compare ARM A9's & ARM A15's performance to intel's haswell platform... You would know ARM processors really can't compete on the same level. There's a reason for that price difference
lyeoh - Monday, June 24, 2013 - link
OK, so which review site is better? So that we can go read it as well...whyso - Monday, June 24, 2013 - link
You know what would be nice. GPU benchmarks for the rmbp 13" or HD 4000 from a standard voltage part to see how it compares to the HD 5000.tipoo - Monday, June 24, 2013 - link
Agreed. It can be confusing when the ULV parts have the same name as normal TDP parts and perform significanlty differently.tecsi - Monday, June 24, 2013 - link
Could these MBAs support external 4k displays given the Intel 5000? There appears to be a new Thunderbolt part—is this Thunderbolt 2? I am surmising that this support could be turned on in MBAs when the Mac Pro arrives with Mavericks, along with potentially Apple 4k displays.tipoo - Monday, June 24, 2013 - link
Not Thunderbolt 2. Only the new Mac Pro has that right now.