P112 B/P BIOS Configuration


B/P BIOS configuration modification procedures are documented in section 6.2 the BP-MAN.ZIP file located here.  This page details the specific configuration of the B/P BIOS boot disk delivered with the GIDE.

The B/P BIOS boot process is a two-stage boot.  The first stage - cold boot from power on or reset - brings up a limited, 64K-only version of B/P BIOS.  The boot can take place from either GIDE partition 0: or the first floppy drive.  (For the purposes of this discussion, the cold boot always takes place from Floppy Drive A:, but it is important to note that GIDE is also a boot device.)  When the cold boot is complete, the following configuration is in effect:

Boot Image:

bulletDrive A: is Floppy A:
bulletDrive B: is Floppy B:
bulletDrive F: is GIDE 0: on Master IDE (8MB Partition)
bulletDrive G: is GIDE 1: on Master IDE (8MB partition)
bullet9600 baud, 8N1, no handshaking

(IDE partitions are kept relatively small to minimize the impact on TPA memory allocation.)

After the cold boot has completed initialization, the banked image can be loaded if the P112 has more than 64K RAM, normally by the same batch file that initialized the boot image.  The banked image is memory-size dependent, so images are available on the boot disk for 128K, 256K, 512K, and 1MB RAM.  The primary difference between the images is the availability and size of the RAM disk.  The 128K image does not have a RAM disk, while the other images provide a RAM disk of varying sizes.

Banked Image:

bulletDrive A: is Floppy A:
bulletDrive B: is Floppy B:
bulletDrive F: is GIDE 0: on Master IDE (8MB Partition)
bulletDrive G: is GIDE 1: on Master IDE (8MB Partition)
bulletDrive H: is GIDE 2: on Master IDE (16MB partition)
bulletDrive I: is GIDE 3: on Master IDE (16MB partition)
bulletDrive J: is GIDE 4: on Master IDE (16MB partition)
bulletDrive M: is the RamDisk (not available on 128K image)
bullet9600 baud, 8N1, no handshaking

(IDE partitions can now be much larger because the Allocation Vector tables are located in banked memory and no longer have an impact on the TPA.  Even so, the size of partitions 0: and 1: cannot be modified without also modifying them for the Boot image, and thus impacting Boot image TPA space.)



The BPCNFG program is used to configure either the boot image stored on the system tracks, or the banked image stored as a file.  The two methods are shown here:

BPCNFG A:                 <-- Open and configure the system track boot image on drive A:
BPCNFG image.img  <--- Open and configure the specified banked image.

Other than the different command-line arguments, the two invocations of BPCNFG operate identically.

Once started, BPCNFG presents a menu of options:

  1. System Options
  2. Character I/O Options
  3. Floppy Subsystem Options
  4. Hard Disk Subsystem Options
  5. Logical Drive Layouts

Although all of the menu options need to be fine-tuned for your P112, only three of them will be discussed here.  The Character I/O Options menu allows you to set the baud rate, parity, stop bits, word size, and handshaking options of all I/O ports.  The purpose of most of these settings is obvious, but the handshaking option requires a little more explanation.

"RTS/CTS = Yes" is the setting for hardware handshaking.  With the P112's terminal port on P4, it actually sets the 80182's ESCC #1 serial port to "Auto Enable" mode, where an active signal on the incoming DCD line is the receiver enable, and an active signal on the incoming CTS line is the transmitter enable.  If you're using this type of handshaking to achieve higher baud rates, bear in mind the setup requirements - both these signals must be active for two-way communications.

The Hard Disk Subsystem menu is where you enable the GIDE controller and enter the IDE drive's Cylinder, Head, and Sector (CHS) values.  These values are normally printed on the drive's label.  This must be accomplished prior to accessing the IDE drive.

Logical Drive Layouts is where you'll change a drive's logical assignment.  With the Boot and Bank configurations shown above, the Floppy drives are A: and B:, while the IDE drive partitions are F:-J:.  With this menu, you can change the assignment of any of the drives.  Normally, after loading the boot and bank images to the IDE drive, you'll want to reassign drives A:-E: to the IDE partitions, and drives F: and G: to the floppy drives.  Thus, when booting from floppy disk, Drive A: is Floppy 0:, but when booting from the GIDE, Drive A: is GIDE partition 0:.



  1. Configuration changes will not take effect until you reset the system.
  2. The B/P BIOS can operate at baud rates to 115.2K, but the P112 ROM is limited to 38.4K.  If you choose to operate above that, the ROM sign-on will be gibberish, but the operating system will boot properly and the B/P BIOS will shift the baud rate to whatever you selected.
  3. There is a bug in the BPCNFG baud rate tables: 56K is listed as 76K.
  4. If you want to add up to two more floppy drives (max = 4) or more IDE partitions (or even a second IDE drive) you'll have to re-compile the BIOS.  While not particularly difficult, it can be a tedious process.  Contact me via e-mail for assistance.

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