You my friend, are an idiot. Use a computer with a bios, and I assure you you can boot from a floppy disk or a usb drive without an MBR. Don't confuse and MBR with a bootable sector, they aren't the same thing, but both perform similar functions. Just because it has a compatibility layer, doesn't mean it's just like the real thing, but I am pretty sure it can still boot from CD, which doesn't have an MBR, or a floppy if you still had something that old laying around. Or, format a usb drive without an MBR, and put one of the development OS's that use custom partition schemes without MBR's that work perfectly on old bios'. Stop pretending like you know anything about how a bios or computer works. Let me explain it, let me know where you get lost.
BIOS Starts up, and initializes all devices. It then checks your boot order you have selected (or default if you haven't gone into your bios). It then loads the FIRST sector of selected device (floppy, hd, cd, usb), whatever, to 0x7C00. It then checks that the last word (that's 2-bytes just incase you know less than i'm giving you credit for) to make sure it's 0xAA55 (also known as the boot signature, this is what tells the bios if this device is bootable or not). After verifying this boot signature (some bios' don't even check it actually, and some have an option to check it or not), it will pass control to the boot loader (aka, first sector of the boot device). The boot loader needs to determine how it wants to treat the boot device. The MOST COMMON method is by using an MBR (master boot record) within the first sector. The boot loader would read the MBR, and by checking the flags of each of the 4 entries, determine which is the bootable partition. Notice, this is the boot loader (boot sector) doing the checking of the MBR, NOT THE BIOS. The bios didn't care what the hell the partitioning method is, all it cares is that it found a boot signature and passed control. Please please please, read up on something before you sound even more retarded than you already do. I would also be willing to bet your motherboard does boot from something other than an MBR, please put a CD in your drive that's bootable and let me know what happens. If you're still not convinced, I could write some code to format a thumb drive with a custom boot loader that has no MBR and displays some random BS to your screen just to prove it's loading, but I doubt you'd follow through with checking since you obviously know more about the boot process than someone that has written multiple boot loaders, partition schemes, file system drives, partitioners, formatters, and a 32-bit multi tasking os of his own.