Mac Musings

SSD: Why the 2010 MacBook Air Is So Fast

Dan Knight - 2010.10.27 - Tip Jar

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Since publishing this column, more facts have come to light about the 2010 MacBook Air (MBA) and its solid-state drives (SSDs). The SSDs are not soldered to the system board, as I had originally believed, but use a new connector, which means they can be replaced. The first SSD upgrades for the MBA. The drives appear to the operating system as SATA drives, and it appears that Apple is using 3 Mb/s SATA II, although the company has not confirmed that. Where this column refers to the SSD as being on the system board, make a mental note that it's connected to the system board via a connector.

"The new MacBook Airs are faster than their predecessors."

That simple statement in Macworld's benchmark report on the new MacBook Air (MBA) models comes as something of a shock when you consider that it applies to the 1.4 GHz 11.6" MacBook Air. In fact, it scores a lot higher than last year's 2.16 GHz mode.

The raw numbers are there: The 11" MBA has an overall Speedmark 6.5 score of 85. The 1.86 GHz 2009 MBA, 54. The 2.13 GHz version, 63.

As for the new 1.86 GHz 13" MacBook Air, it benchmarks at twice the performance of last year's 1.86 GHz model.

What's going on here?

It's the SSD

The biggest change in the MacBook Air is the move from slow 4200 rpm 1.8" hard drives to flash memory for data storage. Macworld reports that duplicating a 1 GB file took five times as long with the 2009 model's hard drive as with the 2010 model's solid-state drive (SSD). In other tests, the new drives came in at 21% faster.

But the surprising thing is that the processor intensive tests also saw huge increases. Those tests aren't supposed to be impacted by hard drive performance, the Core 2 Duo CPUs in the new MacBook Air are not a quantum leap from previous versions, yet "the new 1.86 GHz MacBook Air outperforms its predecessor in processor intensive tasks," according to Macworld.

And Macworld is not alone. Primate Labs has benchmark results using its Geekbench tests. The original 1.6 GHz MBA scores 2031. Last year's 1.86 GHz model rates 2444. This year's 1.86 GHz model achieves 2695, and the 1.4 GHz model comes in at 2026, approaching results for the original 1.6 GHz MBA.

What is going on here? How can SSD make such a difference?

Virtual Memory

In the old days, personal computers had a certain amount of memory installed, and that was it. If you ran out of memory, you had to quit one or more programs to make room. The amount of RAM was all you had.

Then came virtual memory, which allowed you to reserve a certain amount of space on the hard drive where you could swap data from RAM to the hard drive and back again. That was a whole lot slower than using system memory, but it meant that physical RAM was no long an absolute limit.

There was a tradeoff. Enabling virtual memory let you do more, but it also slowed you down. As programmers got smarter about it, they began writing programs where rarely used bits of code would normally be stored in virtual memory, leaving more physical RAM for real work.

The only way to improve virtual memory performance was with a faster hard drive, one that could move data to and from system memory more quickly.

And under old virtual memory schemes, such as the one used by the Classic Mac OS (versions 1.0 through 9.2.2), you were limited to whatever amount of drive space was reserved for virtual memory.

For Mac users, all of that changed with the introduction of Mac OS X. You no longer had to specify how much drive space was available for virtual memory - all free space on your hard drive was available. And you could no longer disable virtual memory; it was an inherent part of the operating system.

The Drive Matters

If you've ever booted the Classic Mac OS from CD, you know how slowly it loads but how quickly it runs once it's finished booting. And if you've ever booted Mac OS X from CD or DVD, you know how slowly it loads and how slowly it runs even after the system is booted. The problem is, OS X depends on virtual memory, and virtual memory depends on a drive you can write to - CDs and DVDs are not writeable and cannot be used for virtual memory, forcing OS X to get by with whatever physical RAM is installed. (Another benefit of the MDA's USB recovery drive is that it uses flash memory, making it a writeable drive.)

For installing the operating system every year or two or recovering from catastrophic drive failure (is there any other kind of drive failure?), that's not such a big deal. It's not something you're doing every day, every week, or every month. But for regular system maintenance, we recommend a separate hard drive or drive partition so you can avoid the Booting From the SuperDrive Blues.

A faster CPU means a faster system. Faster system memory means a faster system. More system memory means a faster system, since it reduced dependency on virtual memory. And a faster hard drive means a faster system - the more virtual memory is used, the more important it is.

2 GB Is No Longer Excessive

When Mac OS X first came to market in March 2001, you could install and run it on a G3 or G4 Mac with 64 MB of memory, although Apple recommended 128 MB. As users quickly discovered, more RAM let it run more quickly by reducing dependence on slow virtual memory.

OS X 10.2 required 96 MB, Apple suggested a minimum of 128 MB, and users recommended 192 MB as a realistic minimum - and 256 MB to 512 MB strongly recommended. With 10.3, 256 MB to 512 MB became the recommendation, and with 10.4 Tiger, you needed 256 MB and ideally had 512 MB to 1 GB.

As someone who uses Tiger daily, I can tell you that every bit of extra system memory improves performance. I've boosted my dual 1 GHz Power Mac G4 from 768 MB (installed when I purchased it secondhand) to 2 GB in incremental steps, and each additional 256 MB or 512 MB of RAM improved performance.

Mac OS X 10.4.4 was the first version for Intel-based Macs, and the Intel and PowerPC versions of Tiger could not run on the other hardware platform.

OS X 10.5 Leopard was the last version to support PowerPC Macs. Leopard required 512 MB, with 1 GB recommended, and the installer wouldn't let you put it on a Mac with less than an 867 MHz G4 CPU, although workarounds were found. OS X 10.5 was the only version that could be universally run on both Intel and PowerPC Macs.

I also use Leopard daily, and my Leopard Mac has less system memory than my Tiger Mac. 1.25 GB of RAM used to sound like a lot, but it's just adequate when you're running a dozen apps at the same time. This Digital Audio Power Mac (upgraded with a dual 1.6 GHz CPU card) only supports 1.5 GB of system memory, and although it would help a bit, I don't anticipate boosting memory any further. At this point I need to start seriously considering getting my first Intel-based Mac.*

OS X 10.6 Snow Leopard, released in August 2009, only runs on Intel-based Macs and requires at least 1 GB of memory. It really needs more than that, and the MacBook Air has always shipped with 2 GB as its only configuration. Problem is, 144 MB to 256 MB of that is used for video, leaving 1.75 GB for the operating system and software.

If you plan on using more than one browser, running Photoshop, or having a lot of programs active at the same time, you'll be using virtual memory in no time at all, which is why it's so nice that Apple finally offers a 4 GB version of the MacBook Air (you have to order it that way; user upgrades are not possible.)

It's That Much Faster

Where previous versions of the MacBook Air used a 4200 rpm hard drive for virtual memory, the 2010 models use fast flash memory. It's far faster - Macworld found copying a 1 GB file was five times as fast on the new MBA's SSD compared with last year's hard drive model.

Because virtual memory is always on, the speed of virtual memory has always been a factor in OS X performance. Until now, we really didn't see a huge difference because hard drives have latency and physical limitations on how quickly they can read and write data. A faster hard drive is somewhat faster than a slower one for virtual memory, but not on the same order as the flash memory in the new MBA.

Not only is SSD faster for disk-based tasks, but because virtual memory is always on, it improves performance for memory-based and CPU-based tests as well.

The Future of MacBooks

Steve Jobs said that the MacBook Air points to the future of MacBooks, and it's already evident that solid-state memory is a quantum leap over even fast hard drives in terms of boosting overall system performance.

CPUs are slowly getting faster, and until now, SSDs have been used to replace hard drives connected to a SATA interface. By putting flash memory on the system board, there's no bottleneck in accessing data, so flash-based MacBooks will boot more quickly, load apps more quickly, open files more quickly, browse the Web more quickly (all browsers cache data to the system drive), and overall do everything more quickly without any change in CPUs.

In short, with the 2010 MacBook Air, Apple has shown us what a significant bottleneck slow notebook hard drives have been. With the possible exception of next revision to the consumer MacBook, expect all future Mac 'Books to include SSDs.

Because Apple isn't competing on the low end of the notebook market and designs its own system boards, it can afford to do this, making a 64 MB or 128 MB SSD standard on the MacBook Air - and probably 256 MB and 512 MB on future MacBook Pro models.

Whither the Hard Drive?

I anticipate a future in which MacBooks no longer have a built-in optical drive and no longer ship by default with a hard drive. That said, I wouldn't be at all surprised to see Apple continue to offer space for an internal notebook hard drive, providing additional storage space for those who find SSDs too small for everything they do.

Within the coming year, I wouldn't be at all surprised to see flash memory replace hard drives in the Mac mini and iMac, and I'd be shocked if the 2011 Mac Pro doesn't have a system board flash drive, as this would really unleash its performance. Hard drives will be for additional storage.

Based on what we've seen with the lower speed CPUs on the 2010 MacBook Air, I look forward to the kind of speed boost we're going to see in future MacBooks and desktop Macs.

System board SSDs will come to the PC world eventually, but that's a world where most brands don't design their own system boards or manufacture their own hardware, choosing to depend on other companies to design and manufacture system boards, other components, and even assemble the end computer in many instances.

The new MacBook Airs are faster than their predecessors thanks to fast system board flash memory, and future Macs will have that same advantage. That's Apple innovation in action!

* I've been using Google Docs spreadsheets for a year or two now, and I recently accessed them on a friend's Windows notebook. Now that I have seen how slow things are on my dual 1.6 GHz G4, it's time to get serious about joining the Intel Mac world. I'm hoping finances will permit that in the not-too-distant future.

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Dan Knight has been using Macs since 1986, sold Macs for several years, supported them for many more years, and has been publishing Low End Mac since April 1997. If you find Dan's articles helpful, please consider making a donation to his tip jar.

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