>Does anyone remember the key combination to gain access into an old IBM AT computer. 8088 days.

If the machine in question actually uses an 8088, then it would be an
original PC or, more likely, an XT. Both use a set of DIP switches on the
motherboard to configure various parameters, and cards are configured by
jumpers or switches. There is no BIOS setup as such on an 8088 machine.

If the machine is actually an IBM AT (or clone), it uses an 80286
processor. 'True blue' IBM ATs, and earler clones, use a setup program on
a floppy disk to configure the system's CMOS NVRAM. Later clones (and
some later motherboards in actual ATs) have a setup program built into the
BIOS, like 'modern' systems.

If your machine is actually an 8088 box, the DIP switch settings can be
found in a book that I have somewhere if I dig for it. If it is an AT (or
clone) which requires a setup disk, it should be possible to find one (or
an image file of one) on the web. If it is a machine with a setup program
in the BIOS (the only scenario in which a key combination would do
anything), then the particular key sequence depends on the particular BIOS
(just like newer systems). Holding DEL, holding F10, hitting
CTRL-ALT-INSERT or CTRL-ALT-ESC, are typical examples.

If you can give me more details, such as the exact model of the machine,
any messages which it displays during bootup, etc., then I might have a
better chance of giving you specifics.