Apple's A5X Die (and Size?) Revealed
by Anand Lal Shimpi on March 15, 2012 5:15 PM ESTiFixit saved us all a whole lot of trouble and performed a teardown of the new iPad announced last week. The internals were mostly what we expected, down to the Qualcomm MDM9600 LTE baseband. Despite many of the new iPad's specs being a known quantity prior to launch, there were a few surprises in the teardown.
First and foremost, Apple has moved away from a PoP (Package-on-Package) stack with the A5X SoC and now uses two discrete DRAM devices. The iPad iFixit took apart featured two 512MB Elpida LP-DDR2 devices on the side of the PCB that doesn't feature the A5X (in yellow, below). The A5 SoC featured a dual-channel (2x32-bit) LP-DDR2 memory interface running at up to an 800MHz data rate.
Elpida, like most DRAM manufacturers, does a terrible job of keeping its part number decoders up to date publicly so these two devices (B4064B2MA-8D-F) aren't well documented. The first character in the part number ("B") tells us that we're looking at mobile/low-power DDR2 memory. The next two characters ("40") typically refer to the device density, the 4 in this case likely means 4Gbit while the 0 is a bit odd since it usually refers to DRAM page-size. It's the fourth and fifth characters that are a bit odd to me ("64"). Usually these tell us the width of the DRAM interface, the 64 would imply something that doesn't appear to be true (initial memory bandwidth numbers don't show any increase in memory bandwidth). It's quite possible that I'm reading the part number incorrectly, so if anyone out there has an updated source on Elpida (and other) DRAM part numbers please do share. Update: The 64 doesn't imply a 64-bit interface as we can see from this datasheet. The two devices are 32-bits wide each, unchanged from A5 implementations. Thanks ltcommanderdata!
As you might have guessed from the fact that Apple now adorns the A5X with a metal heatspreader, Apple has potentially made the shift from a wirebond package to flip-chip. What you're looking at in the shot above with the heatspreader removed is the bottom of the A5X die. If you were to drill down from above you'd see a layer of logic then several metal layers. Moving to a flip-chip BGA package allows for better removal of heat (the active logic is closer to the heatsink), as well as enabling more IO pins/balls on the package itself. Running gold wires from a die to the package quickly becomes a bottleneck as chip complexity increases.
Note that it is possible for Apple to have used flip-chip in the A5 and simply hidden it under the PoP memory stack. Intel's Medfield for example uses a FC-BGA package but will be covered by DRAM in a PoP configuration.
Update: Chipworks has actually measured the A5X die: 162.94mm^2. This means that our visual inspection was inaccurate and Apple is likely still on a 45nm process, which would explain the unchanged CPU clocks. This also helps explain the move away from a PoP stack. At 45nm the A5X's worst case thermals (heavy GPU load) probably demand much better cooling, hence the direct attach heatspreader + thermal paste.
Using the Toshiba eMMC NAND that resides next to the A5X as a reference, we can come up with a rough idea of die size. Based on Toshiba's public documentation, 24nm eMMC 16GB parts measure 12mm x 16mm. Using photoshop and the mystical power of ratios we come up with a rough estimate of 10.8mm x 10.8mm for the A5X die, or 117.5mm^2. If you remember back to our iPad analysis article, we guessed that conservative scaling on a 32nm process would give Apple a ~125mm^2 die for the A5X. While there's a lot of estimation in our methodology, it appears likely that the A5X's die is built on a 28/32nm process - or at least not a 45nm process. Note that this value is entirely dependent on the dimensions of Toshiba's NAND being accurate as well as the photo being as level and distortion-free as possible.
I'll chime in a little later to talk about A5X SoC performance.
Images courtesy iFixit
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r3loaded - Thursday, March 15, 2012 - link
Hasn't Elpida just filed for bankruptcy? I hope there's enough stock of chips to supply Apple.ltcommanderdata - Thursday, March 15, 2012 - link
http://omapworld.com/4430_8Gb__DDR_PoP_111_1003122...(Document for 8Gb variety but nomenclature should be the same)
The -8D on the Elpida RAM is for LPDDR2-800. It's disappointing that Apple didn't move to LPDDR2-1066 to better feed the stronger GPU.
If the A5X requires a heat spreader and can't use PoP for the RAM, does that make the A5X inappropriate for the next iPhone since the iPhone doesn't really have logic board room to spare for separate RAM chips?
name99 - Thursday, March 15, 2012 - link
My guess is that what we are seeing here is a plan B.Plan A was to use the A6, but that was presumably delayed, so we have Apple scrambling to stick a better GPU on the A5 die, and other niceties were brushed aside. This included DRAM PoP.
I also suspect that we might see an iPad speed bump maybe in November or so, swapping the A6 (and likely also the 9615) into as otherwise unmodified device. Doing so would, among other things, allow Apple to deliver the second part of the "new iPad" message --- we sell devices, not specs, and we upgrade them when we're ready.
If I'm right that a plan B was necessary for this iPad because the world expected a new model announcement in March, then I imagine Apple was mighty pissed off that they were forced into a situation where they had to scramble in this way, and will do everything they can to break future expectations. A speed bump in the second half of the year is the easiest way to do that.
(I suspect they likewise want to get off the "new iPhone expected in July" treadmill. Let's not be surprised if this one is likewise called "new iPhone", NOT iPhone 5, and if Apple likewise --- maybe again in November --- throws in a minor speed bump --- maybe improved flash or better WiFi or something --- to break people's expectations of when iOS devices are updated.)
agent2099 - Thursday, March 15, 2012 - link
Considering the iphone 4S is almost identical hardware to the iphone 4, apple has had 2 years to work on the iphone 5. For this reason I doubt it will be "delayed." I expect a new iphone this summer. We are already at 21 months of the same iphone shell, with apple only upgrading the internals.name99 - Thursday, March 15, 2012 - link
if A6 is delayed because of, eg problems in a new process at the fab, it doesn't matter how long iPhone 5 has been in planning. Unexpected things happen and that is life.gunblade - Thursday, March 15, 2012 - link
I don't believe Apple is using managed NAND yet. So, in this case this should be a standard 8bit synchronous NAND device.Mugur - Friday, March 16, 2012 - link
I believe that the "plot" to have only one iPad, one iPhone like MBP etc. may be true. The fantastic thing about Apple is that they managed to really have no use for better cpu/ram/etc specs in their iDevices. This of course because of their OS/closed ecosystem (you know the saying: "Try to look pretty while doing nothing").Needless to say that this is not what I like, that's why I will probably never own an iDevice...
Of course they will up the specs when really need it (like the GPU for the 2048x1536 screen). In fact, the screen is now the only reason one person outside the Apple magical marketing circle would buy a new iPad for. But besides web browsing, reading and photos, there will be, for a long time, no other application that will use that resolution. All other content will be scaled up from 1024x768 for two reasons: they will have to work on the older model(s) too and the lack of performance from cpu/gpu. It's like buying an 1080p notebook with an entry level (or any level by the way) GPU from NVIDIA or AMD and try to play the latest games at native resolution with every detail maxed out... And for 2048x1536 you need now a Core i7 / Radeon 7970 with a 500W PSU.
Ragashingo - Friday, March 16, 2012 - link
The early benchmarks I've seen floating around showed the new iPad to have GPU performance that exceeded its increase in resolution. Meaning that a game or app on the new iPad can run at full "retina" resolution and still get a performance boost.As for content needing to be scaled. Yeah, that will happen for a bit, but the iOS community is fairly unsympathetic to developers who take too long to update their apps to support the latest thing. Apps not supporting the new screen resolution or new new OS features tend to fall by the wayside and get replaced by ones that do.
UpSpin - Friday, March 16, 2012 - link
pixel resolution got quadrupled compared to the iPad 2GPU performance got doubled (in an ideal wordl) compared to the iPad 2.
A game which runs on the iPad 2 in the native resolution and maxes the GPU out on the iPad 2, will not be able to run in the iPads 3 native resolution with the same effects turned on.
So either they have to upscale the game, thus no use of the retina display in games, or turn off effects, thus worse effects. So a high end game will be forced to upscale. That's simple mathematics.
Steelbom - Friday, March 16, 2012 - link
You said: "But besides web browsing, reading and photos, there will be, for a long time, no other application that will use that resolution. All other content will be scaled up from 1024x768 for two reasons: they will have to work on the older model(s) too and the lack of performance from cpu/gpu."That's not how apps scaling works on iOS. The OS handles everything, which means, all non-OpenGL ES apps will automatically take advantage of the higher resolution. (Text, UI and such.) The only aspect the developer needs to deal with aside from possible minor code tweaking, and I mean minor, is to provide double resolution media.
OpenGL ES games will run at the original resolution until updated, but there's nothing preventing developers from updating. It won't break app compatibility.
Regarding performance, the CPU won't be stressed from the higher resolution and the GPU is enough to handle the higher resolution. Look at Infinity Blade: Dungeons and Sky Gamblers: Air Supremacy, both which were demoed at the Keynote, and they run on the iPad 3. Infinity Blade 2 has been updated already to support the retina display on the iPad 3, as has Real Racing 2, the latter saying it runs at 2048x1536 with 4x AA. No word yet on what Infinity Blade 2 runs at, but I'd expect 2048x1536 as well.