Activate this option if your system contains a Vesa Local Bus (VLB) card that identify itself as an EISA card (such as the Adaptec AHA-284x). When in doubt, say N.
Activate this option if your system contains a PCI to EISA bridge. If your system have both PCI and EISA slots, you certainly need this option. When in doubt, say Y.
Activate this option if your system only have EISA bus (no PCI slots). The Alpha Jensen is an example of such a system. When in doubt, say Y.
By default, the kernel contains a database of all known EISA device names to make the information in sysfs comprehensible to the user. This database increases size of the kernel image by about 40KB, but it gets freed after the system boots up, so it doesn't take up kernel memory. Anyway, if you are building an installation floppy or kernel for an embedded system where kernel image size really matters, you can disable this feature and you'll get device ID instead of names. When in doubt, say Y.