Analyst: iPad 3 GPU mismatched with high-end display

According to a recent analysis released by tech watcher David Kanter, Apple's iPad 3 possesses an unbalanced design, with an underpowered graphics processor for its high-end display. Kanter added that Apple's quick move in releasing the 4^th generation iPad with a graphic chip improved by Samsung's 32nm process technology shows Apple recognised this fault. (See Teardown: The 4th-Gen iPad unraveled.)

Kanter's analysis comes at a time when rumours of Apple's intent to shift some of the manufacturing of its A series processors from Samsung to Taiwan Semiconductor Manufacturing Co. (TSMC) have started to make its rounds. According to some Taiwanese newspapers, TSMC will start trial production of the A6X processor used in the iPad 4 during this quarter. (See Tear Down: Apple's A6X under the microscope.)

Rumors have circulated since March 2011 that Apple will switch from Samsung to TSMC for foundry work. Apple and Samsung are locked in legal battles around the world over patent infringement including one resolved last year in a San Jose trial.

As foundries, Samsung and TSMC both could offer Apple the latest 28 nm processes to bolster performance and lower power for the A series chips. One analyst speculated that Apple may have a long term supply contract for foundry services at Samsung, explaining its slow shift away from its smartphone and tablet competitor. Through much of 2012, TSMC had limited availability of its 28-nm process.

Access to the latest process technology is key for Apple, said Kanter, principal of Real World Technologies. "The high cost and power consumption of the A5X was undoubtedly one of the reasons why Apple opted to discontinue the iPad 3 a mere seven months" after it was launched, he said.

Apple moved quickly to adopt the so-called Retina display from Samsung in the iPad 3 released in March. However, the graphics processor in the A5X chip Apple used—made in a 45-nm Samsung process using "conventional SiON gate dielectrics"—could not adequately feed the new 2048×1536 display, Kanter said.

Superior graphics
"To put this in perspective, AMD and Nvidia were already shipping high-end 28-nm GPUs fabbed by TSMC as early as January 2012, although not in particularly high volumes," Kanter said.

When Samsung's 32-nm high-K metal gate process became available, Apple was able to rev up production of the A6X chip with superior graphics to drive the iPad 4 launched in September.

"Not only did the A6X offer substantially better graphics performance than the previous generation, but the die size is also considerably smaller, at around 123 mm²," Kanter wrote.

Kanter used a ratio of FLOPs/pixel to measure Apple's tablet graphics performance, noting the iPad 3 delivered 198 FLOPs/pixel, far less than the 381 FLOPs/pixel of the iPad 2. "Practically speaking, this means that any 3D applications which were moderately taxing on the iPad 2 could not take advantage of the Retina display."

By adopting the Retina display before competing tablets such as the Google Nexus 10, Apple retained a leadership advantage at the risk of disappointing some users with an under-power GPU in an unbalanced system, Kanter said.

- Rick Merritt
??EE Times