Who is making ARM-based Windows tablets?

Perhaps it goes without saying, but we Microsoft watchers still know very little about the plans of Microsoft hardware partners around Windows 8.

Sure, for a couple of years there have been demos of early hardware (mostly x86-based) running Windows 8. At the recent Computex show, there were even a few details shared by Asus and Toshiba about Windows-on-ARM tablets they're planning, which will run Microsoft's Windows RT operating system.

(Windows RT, formerly known as Windows on ARM, or WOA, is a version of Windows optimized for ARM chips from Nvidia, Texas Instruments, and Qualcomm that's largely similar, though not identical to, Windows 8.)

Reports circulating on June 29 about Hewlett-Packard's plans regarding Windows on ARM -- or lack of such plans -- got me thinking about which PC makers have committed to producing ARM-based Windows hardware.

Asus and Toshiba are on board, as is Microsoft (and its manufacturing partner, rumored to be Pegatron). Microsoft will sell a Windows RT, Microsoft-branded Surface machine, officials said recently, which should be out once Windows 8 is generally available. (That date is expected to be on or around October 2012.) And Acer is planning to join the Windows ARM tablet roster in the first quarter of 2013, Acer officials said in June of this year, although the company has yet to show publicly any Windows RT tablets.

Hewlett-Packard officials have not said in any formal capacity that the company is going to deliver an ARM-based tablet, as far as I can tell. There have been rumors about such a move for months, but I can't find or recall anyone seeing or demonstrating an HP-branded ARM tablet running Windows. There are also rumors Dell may be planning an ARM-based Windows 8 tablet, but nothing official from the company, as far as I know.

On June 29, Bloomberg got an HP representative on record as saying HP's plan is to start with machines running Windows 8 on Intel x86 chips. The first HP Windows 8 tablet deliverable is going to be a business-targeted tablet.

Via a tweet, Bloomberg also noted that the HP representative said this plan was already on the books before Microsoft showed off early prototypes of Microsoft-branded Surface tablets running on both ARM and x86 processors earlier this month -- flying in the face of another June 29 report by the SemiAccurate site that claimed HP cancelled plans to do a Windows RT tablet because company officials were angry about Microsoft's Surface.

There are supposedly "several" Windows RT tablets in the pipeline, I've heard. But when I asked Microsoft today for a list of which companies are committed, I was told by a representative that the list is not public.

Microsoft officials have said that the new ARM-based Microsoft Surface tablets will be out when Windows 8 is generally available, which most company watchers believe will be this fall, most likely in October. The Intel-based Microsoft Surface tablets will be out three months after the Windows RT ones are delivered, Microsoft executives also have said.

Microsoft is privately testing Windows RT in-house and with select partners. So far, independent reviewers have not been provided with Windows RT tablets to test (again, as far as I know).