AMI Plus BIOS, also nicknamed "AMI Pre-Color BIOS" by enthusiasts since it predates the AMI Hi-Flex BIOS (first version with 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 the BIOS string section for further info).
Setup utility
Very early releases of AMI Plus BIOS included a limited, quirky setup utility which displayed all settings one-by-one (with the setup exit prompt displayed last) instead of displaying all at once, requiring going through all settings and skipping the ones that shouldn't be changed until the exit setup prompt is displayed, each time the setup utility is run. At some later point a new, easier to use setup utility with more options was included, displaying all settings at once, including the exit prompt.
Some board manufacturers like PCChips and TriGem also used their own setup utilities with AMI Plus BIOS, which are different from the default utilitİes included by AMI.
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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
Main page: AMIDIAG
AMIDIAG is 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 software.
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 the default setup utilities included with the BIOS allow configurations of hard disks up to 32 GB, only hard drives up to 504 MB can be used in most cases due to lack of LBA (Logical Block Addressing) in most versions, which was never officially included with Plus BIOS. Although some very late code forks such as the TriGem version has LBA. Various workarounds also exist for this limitation, such as using Ontrack Disk Manager.
Identification string
AMI Plus BIOS also introduced a new 16/17-character format for the identification string, compared to the older format used with 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 for 17 character strings, 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 to indicate the CMOS setup type "DE" (for 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.