Each partition on the HD has a certain amount of memory buffers assigned to it, which you can see (and temporarily change) using the addbuffers command. The boot-time buffer sizes can be changed via HD partitioning software like HDToolbox.
If you want to boot the game from floppy with the HD still attached, hold down both mouse buttons on reboot to get to the boot menu and disable all the HD partitions. When it boots it'll then be like the HD was not attached.
