Chainload non-EFI Linux from EFI Linux

Solution 1:

AFAIK, the only boot managers that can chain load from EFI mode to BIOS/CSM/legacy mode are:

• Your firmware's boot manager. Details vary greatly from one firmware to another, but in general, you'd hit a function key (or sometimes Esc) early in the boot process.
• My rEFInd boot manager. To use this option, you must uncomment the scanfor line in refind.conf and ensure that hdbios is among the options on that line. This option isn't 100% reliable, though; some motherboards don't support it, and even if your firmware does support it, the feature will probably boot only from the first hard disk.