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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Kaboose - Thursday, March 15, 2012 - link
Nice little article, I hate how apple hasn't moved up from 16GB base model to 32GB (especially since most apps more then doubled in size!)michael2k - Thursday, March 15, 2012 - link
They are size constrained; they chose instead to make the battery bigger.When they can move back to PoP and stack the DRAM on top of the CPU they will have enough space, again, to increase the flash on the thing.
Or they might figure out how to make the screen more efficient, reducing the number of LEDs, thereby shrinking the battery, and making more space for storage.
Peanutsrevenge - Thursday, March 15, 2012 - link
Yea, gotta hate how big those microSD cards are!That's an idea, allow consumers to upgrade their own storage, wow, that's a bloody great idea!
parlour - Thursday, March 15, 2012 - link
Bad idea from a user experience perspective. Having to manage where things end up is very confusing and hard to get right. If the OS tries to do it, it’s bound to confuse users, if the user has to do it there has to be this whole other level of file management on top of everything.One example: So there is an app in the internal memory and it needs more space, so it saves some of its stuff on the card. What happens when the user takes out the card? That's not unsolvable problem, mind you, but it adds unneeded complexity.
(I’m not sure about this, but isn’t speed also a concern here? If apps on external memory load slower user experience suffers.)
artemicion - Thursday, March 15, 2012 - link
Very apt observation. Illustrates the difference between design focused on end-user-experience and design focused on features. Apple haters tend to favor the products with the longer spec sheets whereas Apple loyalists tend to favor products that are simpler because less options = less clutter.Rather fruitless to debate which camp is "right." Personally, I prefer the more open experience of PCs on my desktop and prefer the simpler Apple experience on my mobile devices.
yankeeDDL - Friday, March 16, 2012 - link
Well, I am an Android user and for me non-removable microSD is a deal breaker, also on Android phones.It goes beyond my comprehension why Google decided not to have a removable microSD on the Nexus S, which is "huge".
I don't remove my SD card very often, but there are times where I find it priceless (e.g.: updating my music -which can take some time while I make up my mind- without having to stay plugged in).
I do see the point about less option vs more features. Personally, I think Apple does not give the freedom to upgrade the microSD so they can charge $100 more to go from 16GB to 32GB (http://store.apple.com/us/browse/home/shop_ipad/fa... while a 16GB microSD class10 costs $18 (http://www.newegg.com/Product/Product.aspx?Item=N8... and you can get 16GB for cheaper with lower speed class.
They do it because they can. I'd do the same if I was them.
gorash - Thursday, March 15, 2012 - link
Honestly, we're not 6 year olds... Even if we couldn't store apps on memory cards, we can at least store movies and photos and music on SD cards.dagamer34 - Thursday, March 15, 2012 - link
You expect too much from your average user.defter - Friday, March 16, 2012 - link
That's a poor excuse. This problem can be solved easily if apps that are installed to the memory, don't use memory card by default.The real reason for omitting memory card slot is greed. 16GB microSD card costs $16 in retail Apple is paying a lot less for it. Thus Apple takes $10-12 worth of memory and sells it for $100 (price difference between 16GB and 32GB models), quite a good business.
This is also the reason why they are still selling 16GB model. If they would increase the minimum memory size to 32GB then the cheapest Ipad wouldn't look that cheap anymore. And if they would sell 32GB model for $499, then they would lose 16GB.
Lack of memory card slot also means that the only way to increase your memory is to buy a new device. This also benefits Apple, since there are users who are happy with their device otherwise, but want more memory.
Unfortunately, most of the consumers are quite stupid and they are wooed by cheap initial prices (oooh, Ipad is only $499, Iphone is cheap with contract). They don't realize that by choosing inflexible products they are paying much more in the end.
name99 - Thursday, March 15, 2012 - link
Yes yes, you hate non-removable batteries and no USB port the lack of an ability to add a slow crappy external memory to your device. We've heard it a thousand times already.Go buy a fscking playbook or whatever it is you want and stop wasting our time with the same damn complaints we've been hearing since the original iPhone.