I have a confession to make. For the past year I’ve been using a
27-inch iMac as my primary workstation. I always said that if I had a
less mobile lifestyle the iMac is probably the machine I’d end up with
(that was prior to the announcement of the new Mac Pro of course). This
past year has been the most insane in terms of travel, so it wasn’t a
lack of mobility that kept me on the iMac but rather a desire to test
Apple’s new Fusion Drive over the long haul.
It’s entirely possible to mask the overwhelmingly bad experience of a
hard drive in a high performance machine by only sampling at the
beginning of the journey. When the OS is a clean install, the drive is
mostly empty and thus operating at its peak performance. Obviously
Apple’s Fusion Drive is designed to mitigate the inevitable performance
degradation, and my initial take on it after about a month of use was
very good - but would it last?
I’m happy to report that it actually did. So today’s confession is
really a two-parter: I’ve been using an iMac for the past year, and I’ve
been using a hard drive as a part of my primary storage for the past
year. Yeesh, I never thought I’d do either of those things.
|
Apple 2013 iMac |
|
Configuration |
21.5-inch iMac |
21.5-inch Upgraded iMac |
27-inch iMac |
27-inch Upgraded iMac |
|
Display |
21.5-inch 1920 x 1080 |
21.5-inch 1920 x 1080 |
27-inch 2560 x 1440 |
27-inch 2560 x 1440 |
|
CPU (Base/Turbo) |
Intel Core i5-4570R (2.7GHz/3.2GHz) |
Intel Core i5-4570S (2.9GHz/3.6GHz) |
Intel Core i5-4570 (3.2GHz/3.6GHz) |
Intel Core i5-4670 (3.4/3.8GHz) |
|
GPU |
Intel Iris Pro 5200 |
NVIDIA GeForce GT 750M (1GB GDDR5) |
NVIDIA GeForce GT 755M (1GB GDDR5) |
NVIDIA GeForce GTX 775M (2GB GDDR5) |
|
RAM |
8GB DDR3-1600 |
8GB DDR3-1600 |
8GB DDR3-1600 |
8GB DDR3-1600
|
|
Storage |
1TB 5400RPM |
1TB 5400RPM |
1TB 7200RPM |
1TB 7200RPM |
|
WiFi |
802.11ac |
|
I/O |
4 x USB 3.0, 2 x Thunderbolt, 1 x GigE, SDXC reader, headphone jack |
|
Starting Price |
$1299 |
$1499 |
$1799 |
$1999 |
This year the iMacs get incrementally better. Displays and resolutions
are the same, but silicon options are a bit quicker, 802.11ac is on deck
and the SSDs all move to PCIe (including Fusion Drive). As tempted as I
was to begin my first look at the 2013 iMac evaluating the impact of
going to faster storage, it was the entry-level model that grabbed my
attention first because of a little piece of silicon we’ve come to know
as Crystalwell.
The CPU: Haswell with an Optional Crystalwell
The entry level 21.5-inch iMac is one of the most affordable options in
Apple’s lineup. At $1499 Apple will typically sell you a dual-core
notebook of some sort, but here you get no less than a quad-core, 65W
Core i5-4570R. That’s four cores running at 2.7GHz, and capable of
hitting up to 3.2GHz. In practice I pretty much always saw the cores
running at 3.0GHz regardless of workload. I’d see some excursions up at
3.1GHz but for the most part you’re effectively buying a 3GHz Haswell
system.
The R at the end of the SKU connotes something very special. Not only
do you get Intel’s fastest GPU configuration (40 EUs running at up to
1.15GHz), but you also get 128MB of on-package eDRAM. The combination of
the two gives you a new brand: Intel’s Iris Pro 5200.
The Iris Pro 5200 is a GPU configuration option I expect to see on the
15-inch MacBook Pro with Retina Display, and its presence on the iMac
tells us how it’ll be done. In last year’s iMacs, Apple picked from a
selection of NVIDIA discrete GPUs. This year, the entry level 21.5-inch
model gets Iris Pro 5200 while the rest feature updated NVIDIA Kepler
discrete GPUs. It’s the same bifurcation that I expect to find on the
15-inch MacBook Pro with Retina Display. As we found in our preview of
Intel’s Iris Pro 5200, in its fastest implementation the GPU isn’t
enough to outperform NVIDIA’s GeForce GT 650M (found in the 2012 15-inch
rMBP). Apple’s engineers aren’t particularly fond of performance
regressions, so the NVIDIA GPUs stick around for those who need them,
and for the first time we get a truly decent integrated option from
Intel.
Most PC OEMs appear to have gone the opposite route - choosing NVIDIA’s
low-end discrete graphics over Intel’s Iris Pro. The two end up being
fairly similar in cost (with Intel getting the slight edge it seems).
With NVIDIA you can get better performance, while Intel should deliver
somewhat lower power consumption and an obvious reduction in board area.
I suspect Iris Pro probably came in a bit slower than even Apple
expected, but given that Apple asked Intel to build the thing it
probably felt a bit compelled to use it somewhere. Plus there’s the
whole believing in the strategy aspect of all of this. If Apple could
shift most of its designs exclusively to processor graphics, it would
actually be able to realize board and power savings which would have an
impact on industrial design. We’re just not there yet. Whether we ever
get there depends on just how aggressive Intel is on the graphics front.
I already went through what the 128MB eDRAM (codename Crystalwell) gets
you, but in short that massive on-package memory acts as a L4 cache for
both the CPU and GPU. You get 50GB/s of bandwidth in both directions,
and access latency somewhere between L3 cache and main memory requests.
OS X doesn’t seem to acknowledge Crystalwell’s presence, but it’s
definitely there and operational (you can tell by looking at the GPU
performance results). Some very specific workloads can benefit
handsomely from the large eDRAM. At boot I suspect key parts of the OS
are probably cached on-package as well, something that’ll have big
implications for power usage in mobile. Unfortunately my review sample
came with a hard drive, and these new iMacs aren’t super easy to break
into (not to mention that Apple frowns upon that sort of behavior with
their review samples), which hampered the user experience. OS X
continues to do a good job of keeping things cached in memory, and the
iMac’s 8GB default configuration helps there tremendously. Whenever I
was working with data and apps in memory, the system felt quite snappy.
I’ll get to the benchmarks in a moment.
The non-gaming experience with Iris Pro under OS X seemed fine. I
noticed a graphical glitch under Safari in 10.8.5 (I saw tearing while
scrolling down a long list of iCloud tabs) but otherwise everything else
looked good.
|
iMac (Late 2013) CPU Options |
|
|
21.5-inch |
27-inch |
|
|
Base |
Upgraded |
Optional |
Base |
Upgraded |
Optional |
|
Intel CPU |
i5-4570R |
i5-4570S |
i7-4770S |
i5-4570 |
i5-4670 |
i7-4771 |
|
Cores / Threads |
4 / 4 |
4 / 4 |
4 / 8 |
4 / 4 |
4 / 4 |
4 / 8 |
|
Base Clock |
2.7GHz |
2.9GHz |
3.1GHz |
3.2GHz |
3.4GHz |
3.5GHz |
|
Max Turbo |
3.2GHz |
3.6GHz |
3.9GHz |
3.6GHz |
3.8GHz |
3.9GHz |
|
L3 Cache |
4MB |
6MB |
8MB |
6MB |
6MB |
8MB |
|
TDP |
65W |
65W |
65W |
65W |
84W |
84W |
|
VT-x / VT-d |
Y / Y |
Y / Y |
Y / Y |
Y / Y |
Y / Y |
Y / Y |
|
TSX-NI |
N |
Y |
Y |
Y |
Y |
Y |
In typical Intel fashion, you get nothing for free. The 128MB of eDRAM
comes at the expense of a smaller L3 cache, in this case 4MB shared by
all four cores (and the GPU). Note that this tradeoff also exists on the
higher end Core i7 R-series SKU, but 6MB of L3 is somehow less
bothersome than 4MB. This is the lowest core:L3 cache ratio of any
modern Intel Core series processor. The 128MB eDRAM likely more than
makes up for this reduction, and I do wonder if this isn’t a sign of
things to come from Intel. A shift towards smaller, even lower latency
L3 caches might make sense if you’ve got a massive eDRAM array backing
it all up.
I have a confession to make. For the past year I’ve been using a
27-inch iMac as my primary workstation. I always said that if I had a
less mobile lifestyle the iMac is probably the machine I’d end up with
(that was prior to the announcement of the new Mac Pro of course). This
past year has been the most insane in terms of travel, so it wasn’t a
lack of mobility that kept me on the iMac but rather a desire to test
Apple’s new Fusion Drive over the long haul.