"Apple is testing multiple next-generation iPhones, and we have independently heard that at least one of these devices sports a brand new display," declares 9to5Mac. See also iPhone 5 release date, specs and rumour round-up.

It's unclear what 9to5Mac means by "independently heard." "Dependently heard" makes more sense, since they're depending on at least one person or perhaps on another rumor site for the assertions. But needless to say, there's not a hint of who the source might be. Electricpig charitably if unjustifiably assumes in its headline that 9to5Mac has a "secret source," and later, with even more charity and even less justification, assumes it's a "secret insider." Visit New iPhone 5 to have flexible display.

Apple is testing "a few next-generation iPhone candidates," 9to5Mac claims. Two of these candidates have "a larger display," specifically 3.999 inches diagonally. "Apple will not just increase the size of the display and leave the current resolution, but will actually be adding pixels to the display," according to the website. Go to iPhone 5 will "launch" in September.

9to5Mac doesn't reference The Verge post several weeks ago that laid all this out, but here it is, one of the rare iPhone 5 blog posts that was genuinely speculative. The Verge post explains that by changing the iPhone's aspect ratio from the current 3:2 to 9:5, Apple could create an iPhone with a significantly larger screen area but keep the same overall phone dimensions. The screen would have the same width, 1.84 inches, but would be longer 3.49 inches compared to the current 2.91. Importantly, that change would preserve Apple's Retina Display pixel density.

One difference between The Verge and 9to5Mac is that the former speculated that the new vertical pixel total is 1152 and the latter asserts that it's 1136. John Gruber, at Daring Fireball, thinks the 1136 number makes more sense: His calculations show 1136x640 pixels would be "one pixel away" from a 16:9 aspect ratio. Take a look at Group test: What's the best smartphone?

iphone 5 3.9-inch

"We've also heard that Apple will be taking full advantage of their new pixels," announces 9to5Mac, as though this would be a change from Apple's lax past practice of letting all those pixels go to waste.

"Apple is currently testing builds of iOS 6 that are custom-built to the new iPhone's display. These builds include a tweaked home screen with a fifth row of icons (besides the stationary app dock) and extended application user interfaces that offer views of more content," according to 9to5Mac.

They seem to be suggesting that iPhone 5 would have a unique version of the iOS firmware, which seems unlikely, to put it mildly. Rollup assumes iOS would have code to detect that it's being installed on a bigger-screened iPhone and then make whatever adjustments the UI would require.

In a separate post related to the possible pixel/aspect ratio change, Gruber says it would add some work and complexity for developers, but Apple could have an option for minimizing that. "iPhone apps are already expected to be at least somewhat flexible in height," he explains. "In short, 'windows' on iOS resize like windows on a Mac. Except instead of the user being able to resize the window in both dimensions to any arbitrary size, on iOS 'windows' are expected to resize only in one dimension."

If, as some expect, Apple introduces iOS 6 at its upcoming Worldwide Developers Conference, it could encourage developers to be flexible "by changing the way notification banners are displayed," Gruber says. Currently, these banners "are shown one at a time, and cover the content of the underlying app." If Apple adopts something like WebOS format, then the banners would "stack" on the screen, and the app shrinks to fit the remaining space.

"If Apple introduced something like this in iOS 6, they could encourage iOS developers to adopt the recommended APIs to be responsive to changes in available vertical screen space," Gruber speculates. "For now, they could pitch this in the context of shrinking screen space in response to on-screen notification banners, but, come October, apps that do the right thing would automatically be responsive to, say, a new device with 176 more pixels."

Whatever 9to5Mac "independently heard," it apparently didn't hear much in the way of details about all these test units floating around. The post says nothing about the screen size of the other units, or in what ways the two 3.999-inch units are otherwise alike or different.