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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name99 - Thursday, March 15, 2012 - link
(a) How many people do you know who are using their MacBook Pro SD card slot as a hard drive? Why not? Because SD is slow crappy storage.(b) If all you want is to to suck in photos off SD-cards (the reason Apple added SD-card readers to MacBooks) buy the damn iPad camera kit. It sells in any Apple store. It has been around for at least a year, maybe two years.
Look, Apple sells the product it sells. The way it wants to do things in this (iOS) space has been obvious for at least five years. Complaining that they won't adapt their ways to suit what you CLAIM you want (and let's be honest, you're not going to buy an iPad even if they do every damn thing you ask for) is a waste of everyone's time.
gorash - Thursday, March 15, 2012 - link
1. That depends on the SD card, of course. SD cards are getting faster.2. Great, so now I have to buy a $30 dongle sticking out just to use an SD card? That would make the iPad less portable, a device which is supposed to be portable.
gorash - Thursday, March 15, 2012 - link
Let's face it, the real reason why they didn't include an SD slot is so people will buy their overpriced internal memories.FATCamaro - Friday, March 16, 2012 - link
No, SDCards are slow. This is why they haven't been traditionally used in high end DSLRs.havoti97 - Friday, March 16, 2012 - link
I don't need the lastest and greastest SATA III bandwidth to stream movies off an SD card. Of course the moment Apple includes the SD slot, it will render the 32 and 64GB models unattractive to 99% of the potential buyers.Einy0 - Friday, March 16, 2012 - link
Yes, slower than top end CF cards. I hardly call 20-30 MB/s slow especially for music and movie files. Someone else hit the nail on the head, Apple doesn't put as SD card slot because people won't buy their over-priced higher capacity versions if they did.KitsuneKnight - Friday, March 16, 2012 - link
Top end SDcards might be able to get slightly decent sequential performance, but they're still horrible for random read/writes (which are always what hurts you the most).I sprung for an expensive 32GB SD card (the highest Class I could find... I'd have to dig it out of the phone to be sure the exact one), and the performance was still crap. Sure, sure, it's fine for playing movies/music, but those are ideal situations for it... large sequential files!
For other things? Not so much.
Dug - Friday, March 16, 2012 - link
Macbooks have an SD card to transfer content to the Macbook, such as pictures from camera. It's not used as a storage device.You can transfer data from SD to iPad too with an adapter. They didn't add it because of space. And most people will use icloud or any other computer to get their data anyway.
No one in their right mind would keep anything of value on and SD card. They are crappy and they do fail all the time.
Kristian Vättö - Thursday, March 15, 2012 - link
I think Apple has concentrated on other components and increasing the storage would not fit in the bill of materials. NAND is priced per GB so you don't get more GB for more money when buying bigger capacities, hence 32GB costs about twice as much as 16GB.solipsism - Thursday, March 15, 2012 - link
I wouldn't be surprised if the additional cost in component materials has reduced their profit margin with this 3rd gen iPad. All of this tech seems well ahead of the curve for a $499 entry price.