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AST RESEARCH TECHNICAL BULLETIN TB-0035 7-25-84
SWITCH SETTINGS FOR THE COMPAQ PORTABLE
Before one can reconfigure a COMPAQ (without hard disk), one must
first determine the revision of the ROM BIOS.
There are a few ways to do this. One way is to look on the
motherboard at the ROM chip, the revision should be indicated
there. The revision is also within the ROM chip, located at
F000:FFE6, in the format 'X COMPAQ', where X is the revision.*
Another way to determine the revision of the BIOS is from the
serial number. If the serial number is above 36792, then it is a
Rev. C, and if it is below, then it is a Rev. B. The COMPAQ Plus
(with hard disk) is a Rev. C.
To date, there are two revisions of BIOS in the COMPAQ portables;
Rev. B, and Rev. C. Revision A was preliminary and never shipped
installed.
Configuring a Revision B;
Consult your AST manual and use the switch settings for a PC-1.
All portables without hard disks and are a Rev. B, will have
two switch blocks.
Switch block 1 is indicated on the motherboard as 'SW1'. It
is located in the left rear corner on the motherboard,
partially hidden beneath the cooling fan.
Switch block 2 is indicated on the motherboard as 'SW2'. It
is located to the right and forward of switch block one.
When configuring, be sure to record the original switch
settings on both blocks, in case there is a problem you
won't have any trouble reconfiguring the way it was.
Configuring a Revision C;
Consult your AST mnnual and use the switch setting for an XT/
A revsion C may or may not have two switch blocks. If you
have a hard disk, you probably have only one switch block.
If in the event you have two, or you have a COMPAQ (without
the hard disk), you still use the setting for an XT. Switch
block 1, SW1, is disabled internally and not used. So the
switch block 2 is to be considered as the only switch block
on the motherboard.
Switch block 2, the only switch block you will use, is
located in the left rear corner of the motherboard.