You may want to boot to DOS to start Linux from a DOS prompt using Loadlin. The kernel and loadlin are installed onto the onboard Flash when the Linux option is pre-installed at the factory. This is also useful for using an NFS root file system
All TS Single Board Computers come with DOS installed on onboard Flash. Usually this is bypassed and Linux runs from Compact Flash or DiskOnChip. In some cases you can also boot to DOS from the CF or DOC. If Syslinux is the bootloader you can type "DOS" at the boot prompt to run ROM-DOS.
To boot to DOS, change the CMOS settings, see ways to boot an OS on the SBC for instructions.