Microsoft plans to launch at least one Surface all-in-one PC next month, reports ZDNet. The company has been testing 21-inch, 24-inch, and 27-inch models for quite some time, but it is unclear which variant it plans to launch at its event in October. ZDNet reports:I've heard that Surface Cardinal could be positioned as a product that can turn your desk into "a studio." My bet: Cardinal is the rumored Surface All-in-One device running Windows 10, which may come in one, two and/or three different screen sizes (21, 24 or 27), as first reported by Windows Central. This may be the consumer-focused version of Microsoft's Surface Hub, as Windows Central speculated, using the Perceptive Pixel screen technology that's at the core of Surface Hub.