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Saturday, April 03, 2010, 05:00 pm PT (08:00 pm ET)

iFixit's iPad teardown finds huge dual battery, 256MB of RAM in A4 [u]

Investigative work by the team at iFixIt has revealed a series of interesting details about the iPad's internal details, including a large battery and RAM incorporated within its A4 System on a Chip.

The company's teardown reveals that the iPad's battery has 5.5 times the capacity of the iPhone. It's actually two battery packs wired in parallel, the company reports, providing a total of 24.8 Watt-hours. "In contrast," the report notes, "the iPhone 3GS has a 4.51 watt-hour battery and the MacBook Air has a 40 watt-hour battery."

On average, the device "sips just 2.5 Watts. That's 1/5 the power of a compact fluorescent bulb," the report states. Even so, the larger battery demands more charging power than standard USB ports provide. It needs its included 10 watt charger, and won't charge while syncing with a standard USB-equipped Mac or PC.

A4 includes system RAM

"The A4 is a Package-on-Package (PoP), with at least three layers of circuitry layered on top of each other," the site notes. Apple's "A4 is packaged just like the iPhone processors, microprocessor in one package and two memory modules in the other package. They're all sandwiched together in a very nice and thin PoP.

"The iPad RAM is inside the A4 processor package. Confirming this took quite a bit of sleuthing: we had to partner with Chipworks to X-ray the processor. The X-ray revealed two layers of RAM. In addition to the ARM processor, the A4 package contains two stacked Samsung dies. We will be releasing a detailed analysis of the A4 in conjunction with Chipworks in a few days."

The A4 contains "256MB of memory per die, for 512 MB total" the company's teardown notes. That's twice the system RAM of last year's iPhone 3GS and third generation iPod touch.

Update: iFixit updated their report to note that the iPad actually incorporates the same 256MB of system RAM as the iPhone 3GS.

iFixIt iPad teardown preview


Physical features

"The rear case is machined from a single billet of aluminum, increasing weight but greatly improving the rigidity of the device," iFixIt reports, adding that "the empty void in the upper right corner [of the WiFi-only model] is where the cellular communications board would go in the 3G iPad."

The iPad's "touch circuit design is more similar to the old 2G and early 3G iPhones than the current 3GS," the teardown revealed. "Chipworks informed us that 'there is so much room in the iPad that Apple didn't need to use small chips, just the right ones and cheap ones.'"

Additionally, the rumored slot that was once imagined to be for a camera "is actually taken up by the ambient light sensor." iFixIt also noted that the iPad's "glass panel is quite thick: about 1.18 mm, compared to the iPhone's 1.02 mm thick glass. This is necessitated by the panel's large size."

The WiFi antennas on the iPad are mounted facing both the front corner and the back, where they penetrate through the solid aluminum back via the window provided by the black plastic Apple logo.