These computers are sometimes confused with the ultra-mobile PC category, which is the name of a platform of small form-factor tablet PCs. UMPCs are smaller than subnotebooks, however both generally run full desktop operating systems such as Windows or Linux, rather than specialized software such as Windows CE, Palm OS, or Internet Tablet OS. Subnotebooks are also sometimes confused with netbooks which are a different category of devices that branched off from mini notebooks in general. Netbooks are most often much less expensive than subnotebooks, as they are optimized for use as portable Internet capable devices and generally lack the processing power of a workstation. Netbooks typically have 9W TDP CPUs, sacrificing performance for power efficiency, whereas subnotebooks often use 18W TDP processors.