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Amiga Technical References

A2286 AT Bridgeboard Information

Jumper and socket locations:

|                                                                   |  
|                               ||J13                               |  
|                                                                   |  
|                                                                   |  
|                                                                   |--
|                                   ||J14    ||J6                 ::| |
|                               ---------------                   ::|F|
|                               |             |                   ::|L|
|                               |             |                J12::|O|
|                               ---------------                   ::|P|
|                              ------------                       ::|P|
|                              | ROM BIOS |                       ::|Y|
|                              |  (odd)   |                       ::| |
|                              ============                         |--
|                              | ROM BIOS |                         |  
|                              | (even)   |                         |  
|                              ------------                         |  
|                             ===J5                                 |  
|                                                                   |  

Comnnecting the battery

Locate the battery connector J13 on the sandwich board. There is only one way the battery connectors fit together.

Jumper Information.

  • J5: RAM configuration, default: 1024 kbytes
    1024 kbytes |     o-o |   640 kbytes | o-o     |

  • J14: Video mode configuration, default: mono
    Color |     o-o |   Mono | o-o     |

  • J12: Floppy disk connector on the sandwich board.

  • J4: Internal floppy disk controller (on the AT-Bridgeboard maninboard), default: enabled
    Disabled |     o-o |   Enabled | o-o     |
    NOTE: When you install the external Floppy/Harddisk controller, you MUST first disable the internal Floppy controller.

  • J6: Internal Floppy disk type, default: 5.25"
    5.25",1.2 MB |     o-o |   3.5", 1.44 MB | o-o     |

Technical Specifications:

Installing an external video adapter
Before powering off the system to place the external video adapter in a PC/XT slot, you have to run PCPrefs from the PC drawer. After double clicking on the icon, you must switch off Mono and Color-video by clicking these items. Use the SAVE command to make these preferences active when booting the AT-Bridgeboard the next time. Power off the system to install the external video adapter.

Using Autoboot system software
NOTE: If you have a real PC hard drive and controller installed, Autoboot will not function!

Autoboot is system software that allows the bridgeboard to use an Amiga file as a PC hard drive. The fake hard drive is emulated at the PC's BIOS level for 100% compatibility. To the PC the Autoboot volume appears as a normal PC hard drive. On the Amiga side the hard drive exists as an AmigaDOS file on any device and directory you choose. Any size PC hard drive can be emulated as long as there is enough room for the Amiga file. This Autoboot file can then be used as a normal hard drive. It can be fdisk'ed, formatted, and made to boot the PC at power up.

To set up an autoboot volume you need to do the following:

  1. Edit your startup-sequence to include this line after the binddrivers command:
    run >nil: sys:pc/pcdisk

  2. Create the Autoboot file on the Amiga. To do this use the makeab command included with the PCInstall disk. Decide where you want the file to be and issue the command:
    makeab drive:directory/filename
    Makeab will now ask you for the number of heads, sectors/track, and number of cylinders to emulate. Autoboot can emulate any type and size of PC hard drive, even hard drives that do not really exist!

    To set up a 10MB fake drive using an Amiga Hard drive you could give makeab the following parameters:
    makeab dh0:fake_c

    Enter number of heads: 4
    Enter sectors/track: 17
    Enter number of cylinders: 306

    Makeab will now print the size of the proposed file and ask you to accept it. You can either restart and choose different parameters, or create the file. If you accept the parameters, makeab will generate the file in the proper format for AutoBoot. Note: makeab creates the file FULL-SIZED and may take a while to create large volumes.

  3. Now that the file is created, you must tell the system where to find it. The system looks for the file ABOOT.CTRL in the SYS:PC/System directory. This file should contain the full path-filename of the file you created with makeab. For this example you would use ed or a suitable editor to create the file sys:PC/System/aboot.ctrl and in this file there should be one line followed by a carriage return:
    which is the name of the file just created. Save this file and you are now finished with the work on the Amiga side. Note: You can have multiple Autoboot volumes and switch between them by changing the contents of ABOOT.CTRL, only one AutoBoot volume can be active at any one time. You must first reboot the Amiga to make the change active.
To use the AutoBoot volume from the PC you will first have to boot the PC with a standard DOS disk. Follow the normal procedure for initializing a PC hard drive, i.e. fdisk and format.
    First run fdisk on the PC. Then partition the fake hard drive. You will normally use the entire disk for the DOS partition, selection 1, but you may also partition the hard drive any way you like.

    Next format the fake drive using the PC format command. If you wish to make the drive bootable you must use the /s option with format. Example:
    Format c: /s
    You may now remove the floppy DOS disk and reboot the PC. The PC will now boot off the AutoBoot volume and you may copy files onto it as a normal PC hard drive.
If you have a real PC hard drive and controller installed, AutoBoot will be disabled!

If your AutoBoot file resides on a FastFilingSystem partition you may need to add the following line to the partition mountlist entry:
  Mask = 0
Since this will slow down all file access to the partition it is recommended that you create a separate partition for the Autoboot file.

If you are using this software with a 2286 AT bridgeboard you must do the following:

Follow the instructons in your user's manual to install the software using the BridgeInstall or BridgeInstall512 program.

  1. After you have installed the software, double click on the icon for the PC drawer to open it.
  2. Double click on the PCPrefs icon to open PCPrefs.
  3. Use the mouse to select D000 memory window. (Do this even if D000 is already selected!)
  4. Click on the save gadget to make the changes permanent.
  5. Reboot the Amiga using Ctrl-Amiga-Amiga.
When the PC boots you should see the message:
  Janus Handler Version x.xx
  Janus Library Version xx.x
You MUST see this message for the Janus software to function properly. If you do not see the message check the following:
  1. The directory Expansion MUST be in the SYS: directory at binddrivers time and MUST contain Janus.library and Janus.Library.info
  2. The directory SYS:PC/System directory must be present at binddrivers time and MUST contain the file PC.Boot and 2500Prefs
  3. The memory window in PCPrefs MUST be set to D000.

Copyright © 2000 Amiga Auckland Inc. All rights reserved.
Revised: June 16, 2005.