Technical speculation on Apple A4
What A4 stands for?
- “A” likely stands for Apple. It’s not clear why “4”. It may indicate quad core? It’s known that Cortex-A9 could have upto 4 cores.
Who designed it?
- Apple bought p.A.semi in Apr/2008. Given that the chip was made at Q4/2009, the T/O should be as early as Q2/2009.
- If PA semi started design A4 from Q3/2008, they only had 3Q to complete the design. This is too short to complete CPU design from the beginning.
- Apple uses Samsung’s S5PC100 AP for iPhone 3GS.This AP uses Cortex-A8, which is single core version. The speed is known as 600 (under clocked from 833MHz), and uses Samsung 45nm tech.
- Samsung is known to push cortex-A8 speed up to 1GHz, and A4 might use this version of CPU (without underclocking), but multi core version. –> Apr/2010 update: From reverse engineering of iPad shows that the A4 is using Cortex A8 single core. It’s known that single core Cortex A8 on 45nm only speed up to 650MHz. So the GHz claim from Apple A4 is considered from Intrisity Hummingbird design that speeds up Cortex A8 to GHz at 45nm. Here is some more details. http://spectrum.ieee.org/semiconductors/processors/evidence-for-intrinsity-in-the-ipad 4 in A4 now turned out that not for “Quad” core.
- It makes sense that iPad uses same software stack as iPhone, so Samsung AP should work fine without big risk. P.A.Semi may work with Samsung to implement in multicore as Cortex-A9.
- Here is come comparison between Cortex-A8 and A9
|core||Single core only||Multi core (1~4)|
|Dhrystone performance||2.0 DMIPS/MHz||2.5 DMIPS/MHz/core|
|Architecture||ARMv7-A Cortex||ARMv7-A Cortex|
|Frequency||600MHz to 1GHz at 65nm||800MHz (worst case, power optimized) using TSMC 40G|
|Power at target frequency||–||0.5W|
|Chips||TI OMAP 3xxxx Samsung S5PC100||TI OMAP 4xxxx ST U8500
Nvidia Tegra 2
|Devices||Apple iPod touch (3rd gen) Apple iPhone 3GS
- Samsung, in fact, #2 AP vendor following TI, so Apple could take advantage of it.
Top-5 Suppliers of Standalone Applications Processors in Q2
(Ranking by Percentage of Revenue)
|4||4||Marvell Technology Group||7.7%||7.4%|
|–||–||Top 5 Companies||65.1%||66.3%|
- Here is some comparison among different iPhone and Palm pre
- Here is a block diagram of Samsung’s S5PC100
- Apple used PowerVR’s SGX as a GPU in iPhone 3GS, but in iPad, they might integrate GPU within A4 package as a SiP. From the introduction video of iPad, Apple hardware VP spent a lot of time explaining how good the graphic performance of iPad. P.A Semi might play a big role here in integrating GPU and CPU in SiP.
- There is a speculation that A4 might use ARM’s Mali GPU together with Cortex (http://www.eetimes.com/showArticle.jhtml?articleID=222700553&pgno=2&printable=true&printable=true), but it’s less likely that Apple changes things too many at once when things work just fine in smaller platform. Next version of A4 might use ARM’s GPU, but considering Apple’s strategy so far, it’s unlikely that Apple relies on both CPU and GPU on the same IP company.
Who makes it?
- It’s highly likely that Si is made from Samsung using 45nm technology, but more pushed version like TGO technology (similar to TSMC’s 40 LPG) to improve the speed.