With the advent of Windows 8 Microsoft will support both traditional x86 processors and new System on a Chip (SoC) architectures, including ARM systems.
The traditional Windows 8 release, designed as the successor of Windows 7 will play nice with existing CPUs, as well as current hardware and software, but will also be compatible with legacy products, especially with older applications.
In contrast, Windows 8 for SoC will not offer compatibility or legacy application support.
According to Renée J. James, Senior Vice President, General Manager, Software and Services Group (via Channel Register), Windows 8 traditional will also feature a Windows 7 Mode.
“Windows 8 traditional means that our customers, or anyone who has an Intel-based or an x86-based product, will be able to run either Windows 7 mode or Windows 8 mode," James revealed. "They'll run all of their old applications, all of their old files – there'll be no issue.
"On ARM, there'll be the new experience, which is very specifically around the mobile experience, specifically around tablet and some limited clamshell, with no legacy OS. Our competitors will not be running legacy applications. Not now. Not ever."
When l first heard of the move, I could not help myself what exactly is Windows 7 Mode in Windows 8?
Customers can already access a Windows Mode when running Windows 7. I’m of course talking about Windows XP Mode, the free, virtualized copy of XP SP3 designed to run inside Windows Virtual PC virtual machines.
James’ mention of Windows 7 Mode could point to a similar virtualized copy of Windows 7 designed for Windows 8 customers.
Source: Windows 8 to Feature Windows 7 Mode - Softpedia