DP Tool Club 8/CDASC08.ISO/VRAC/BIOSHELP.ZIP/BIOSHELP.DOC

Text File | 1993-05-11 | 8.4 KB | 144 lines

    Shadowing:
        Some adapter cards have a BIOS chip which contain code necessary
    for the proper operation of the adapter. For example, VGA cards have
    a VGA BIOS chip with video write routines. The average access time for
    a ROM chip is 170 Ns. This is considered very slow. The average access
    time for motherboard DRAM is 70 or 80 Ns, normally twice as fast as a
    ROM chip. AMI BIOS will set aside an area of memory from C000:0000 to
    C7FF:FFFF. The video adapter BIOS is copyed into this area. Instead of
    accessing the video ROM for video BIOS calls, the system will access
    section of memory to get the proper code. This greatly improves video
    speed. The process of copying video ROM to RAM for faster access is
    called VIDEO BIOS SHADOWING. AMI BIOS will copy itself to another
    section of RAM from F000:0000 to FFFF:FFFF. This is called SYSTEM ROM
    BIOS SHADOWING and greatly enhances system performance. Some older AMI
    BIOS and all new BIOS (dated2/2/92 and after) will also support shadowing
    for other adapters cards which reside at different addresses.

    ADAPTER BIOS ADDRESSING:
        At any address reserved for adapter BIOS, the first two sections of
    the address will contain the numbers '55 AA'. This will be true for any
    BIOS. To confirm this, go into DEBUG. Type 'D C000:0' to see the first
    block of memory in the VGA BIOS. On the screen, the upper-left-most
    characters will be '55 AA'. When having trouble with an adapter, check
    in this manner to see that the BIOS is functioning properly. If the BIOS
    appears okay, check to see that no other peripherals are set to the same
    address. If two adapter cards are suspected to be in conflict, remove
    all but the video card and drive controller and try the cards one at a
    time to see if they function.

    RESET XCMOS:
        For older AMI BIOS (pre-1991) the contents of Extended CMOS Setup
    may be reset to the default values by holding down the INSert key and
    turning on the system. An XCMOS Checksum Error will be generated. This
    error can be corrected by entering XCMOS Setup, writing CMOS registers
    and exit, and rebooting the system. For newer AMI BIOS, the only way to
    load default values for XCMOS is to enter CMOS Setup and select LOAD
    DEFAULT VALUES from the menu.

    AMI PRODUCT PURCHASES:
        AMI Corporate Offices does not do any direct sales of BIOS, manuals,
    hardware or software products to the end user. BIOS and manuals are
    available from Washburn & Co at [phone] or Upgrades Etc at
    [phone]. When calling these companies, proper information must be
    given in order to determine the correct BIOS needed. If the machine has
    AMI BIOS currently, the distributor will need the reference number
    located at the bottom of the AMI copyright screen when the system is
    booted. If the machine does not have AMI BIOS, the distributor needs to
    know what speed the board is and what chipset (e.g. C&T, OPTI, etc.) is
    used. If the machine has cache memory, consult the dealer or manufacturer
    of the board for a new BIOS that will support the cache. For information
    on AMI motherboards or hardware products, contact the AMI Sales
    department to find the nearest dealer.

    PASSWORD FEATURE:
        New AMI BIOS (2/2/91 and later) are equiped with a password feature
    which can be set to ask for a password to enter setup or every time the
    system is booted. Normally this password is set by the computer dealer
    before the user gets the system. Sometimes users may assemble thier own
    system or CMOS information may be lost. In these cases, the following
    information is necessary. When the password feature is first enabled,
    a CURRENT PASSWORD will not exist. The default password is 'AMI'. In
    order to change the password, select the CHANGE PASSWORD option from the
    main menu of the CMOS setup routine. The machine will ask for the CURRENT
    PASSWORD. 'AMI' must be entered at this point. The new password may then
    be entered, then re-entered for confirmation.

    CMOS SETUP:
        It is a popular misconception among new computer users and people
    who are not very involved with hardware that the CMOS is a part of the
    BIOS. The setup program in the BIOS is a very basic interface program
    which only allows the user to put information into the CMOS memory and
    XCMOS registers. The screen for standard setup should be basically self-
    explanatory. Drive types, monitor types, time and date should all be
    easy to enter for the user. The settings in the extended setup really
    have to do with the chipset on the motherboard. Questions on XCMOS should
    be directed to chipset or motherboard manufacturers for BIOS dated pre-
    1991. Any BIOS dated 1991 is in what is called the HI-FLEX format. A
    HI-FLEX BIOS User's Guide is available to help the user understand the
    screens. An appendix is also available to help explain the options in
    the advanced setup so that the user can pick the options best suited
    for his/her environment. The best place to get a good explaination of the
    chipset options is of course the chipset manufacturer.

    CUSTOMIZATIONS:
        Customized BIOS is available from Washburn & Co or Upgrades Etc.
    Examples of customizations are personalized copyright screens, changes
    to the drive table, and having some options absent from the setup menu.
        Some OEM companies have licensed AMI BIOS and are allowed to
    customize the main code for use with thier motherboards. Some examples
    are Everex and Mylex. The motherboard manufacturer must be consulted for
    a BIOS upgrade in these cases. Standard AMI BIOS will not work because
    it would not contain the proprietary changes made by the OEM.Megabytes

    A Megabyte is 1024 Kilobytes, which is 1024 bytes; thus 1 Megabyte is
1024 * 1024 BYTES. 1 Meg actually equals 1,048,576 bytes. Most drive
manufacturers specify the drive capacity in millions of bytes and call it
Megabytes, possibly to make the drive sound larger than it is. AMI BIOS
calculates drive capacity in Megabytes using the follwing calculation:

Millions of Bytes    =    CYL * HEADS * SEC/TRACK * 512 (BYTES PER SECTOR)
Megabytes             =    MILLIONS OF BYTES / 1024 / 1024

    The following example uses a Seagate ST-251:

820 * 6 * 17 * 512 = 42,823,680 million bytes
42,823,680 / 1024 / 1024 = 40.83 MEGABYTES

    In the drive specs provided by Seagate, the ST-251 is listed as a
42 Megabytes drive. The average end-user will become confused when he/she
sees the AMI BIOS calculate 40.8 Megabytes.

Maximum parameters supported by DOS are 1024 cylinders, 64 heads, and
64 sectors per track. Exceptions are EDSI and SCSI, which have BIOS on the
controllers for translation. Also, some IDE drives do their own translation.

    ESDI drives are ALWAYS drive type 1 when using the controller
translation, normally type 47 when not using controller translation.

    SCSI drives are specified as NOT INSTALLED.

    IDE drives don't adhere to the AT bus standards. A provision was made
in the 4/9/90 release of AMI BIOS to be able to use IDE drives. (Some of
the read routines were changed. All other info is proprietary)

    Drive type 47 (user defined) was put into the BIOS in late 1989 and
must have the ScratchRAM option set to 2 (to protect info).

    ERROR NO ROM BASIC can be caused by not having an active partition. The
error means the computer can't find anything to boot from.

    In the new HI-FLEX BIOS, most boards will have the option to shadow
the C000 area. Some boards will have the option to cache this area. This
makes for extremely fast video times.

    C000 cacheing also has one drawback. The caching is done in the 486
8K internal cache. This cache cannot be write-protected. Whenever a BIOS
test is done with AMIDIAG, the program sees that there is a BIOS present.
The program has no knowledge of the Video ROM Cache and will treat the code
as being a normal shadowed BIOS. The program will see that this BIOS is
NOT Write-Protected. A NON WRITE-PROTECTED BIOS is viewed as an error
condition and the BIOS ROM TEST will fail.   Currently, there is no work-around
to
this problem. The BIOS test must be performed with the C000 ROM CACHE
option disabled.