AMI Plus BIOS

POST screen for AMI Plus BIOS

AMI Plus BIOS, commonly nicknamed as AMIBIOS Pre-Color between enthusiasts since it predates the AMI Hi-Flex BIOS (which was the first version to have a colourful setup utility), is a version of AMIBIOS released by American Megatrends in 1987. It is the earliest version of AMIBIOS to include a built-in setup utility for configuring the CMOS settings without booting into a separate floppy disk for setup.

Plus BIOS was also the first and only version of AMIBIOS to include a built-in system diagnostics program, a limited version of AMIDIAG to be exact. Although AMIDIAG was not included with all versions of this BIOS, the ones that have it use "D" or "DE" for the CMOS setup type code in the BIOS string (see #BIOS string section for further info).

Setup Utility

Very early releases of AMI Plus BIOS included a more limited setup utility which requires re-configuration of each setting in the utility entirely each time to change a setting. At some later point a new, more straightforward setup utility was included. Some board manufacturers like PCChips and TriGem also used their own setup utility with AMI Plus BIOS, which look different from AMI's utilities.

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  Early setup utility

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  Late setup utility

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  PC Chips setup

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  Late TriGem setup

AMIDIAG

Limited version of AMIDIAG included with some AMI Plus BIOSes

Main page: AMIDIAG

AMIDIAG was a system diagnostics utility developed by American Megatrends for DOS based operating systems. The version included with some Plus BIOSes is limited compared to the actual, full version of the program.

The following diagnostics are included with the limited Plus BIOS version:

Hard Disk

Note: Hard disk diagnostics are only accessible when a hard disk is detected in AMIDIAG.

• Hard disk format
• Automatic interleave
• Locate & mark bad sectors (Media analysis)
• Performance test
• Seek test
• Read/verify test
• Cylinder read/write test (Check test cyl.)
• List bad tracks (Force bad tracks)

Floppy

• Floppy format
• Drive speed test
• Random read and write test
• Disk change line test

Keyboard

• Scan/ASCII code test

Video

• Sync test
• Adapter test
• Attribute test
• 80x25 display test
• 40x25 display test
• 320x200 graphics test
• 640x200 graphics test
• Page selection test
• Colour test

Miscellaneous

• Printer adapter test
• Communication adapter test

Technical limitations

While default AMI setup utilities allow configuration of hard disks up to approximately 32 GB, due to lack of LBA (Logical Block Addressing) on most versions of AMI Plus BIOS, which it never officially received although some very late code forks might have it, only hard drives of up to 504 MB can be used.

BIOS string

AMI Plus BIOS also introduced a new 16/17-character BIOS string format, compared to the older one used on AMIBIOS 2.2x. The first (or on 17 character strings, first two) character of the string indicates the CMOS setup type. D indicates built-in AMIDIAG diagnostics, E indicates no AMIDIAG but extended CMOS setup, S indicates only regular setup. "DE" was also used occasionally, which indicates both built-in AMIDIAG and extended CMOS setup are available.

The new string is formatted as the following:

D: CMOS setup type, CCC: Chipset type, MMMM: Manufacturer/OEM identification code, SSSSSS: BIOS subcore release date, KK: Keyboard controller (KBC) ID (with second character indicating the model).

DCCC-MMMM-SSSSSS-KK

Note: As stated above, occasionally 17 character strings (instead of 16) were also used, where one extra character is used for the CMOS setup type section for "DE" (built-in AMIDIAG diagnostics and extended CMOS setup)

Example string: D286-1277-043089-K0

This string is for a 04/30/89 (April 30, 1989; date is in American format) dated subcore AMI Plus BIOS with regular CMOS setup and built-in diagnostics ("D") for a machine with a discrete i286 logic ("286") and a default/unknown keyboard controller (K"0") made by Trangg Bow Co. ("1277").

The manufacturer, chipset and keyboard controller codes can be found here.