Token Ring LANstations with DOS 5 and LAN Manager 2.x

Following the recent release of the Token Ring LANstation we have identified a number of configuration issues when the machine is used in conjunction with DOS 5 and Microsoft LAN Manager 2. The configuration issues only become apparent when using Upper Memory Blocks to high-load device drivers.

The problem occurs because the Token Ring adapter uses a block of shared RAM that APRUMB.SYS uses by default. The solution, therefore, is to exclude the portion of memory that the Token Ring module uses to prevent the module failing to initialize the network stack.

For example, if the LANstation is being connected to a standard LAN Manager 2 network and the shared RAM space in the reference/setup disk has been set to 16K, the APRUMB.SYS line within CONFIG.SYS should read:

DEVICE=C:\DOS\APRUMB.SYS /X:C000-C800

This is because the shared RAM space of the Token Ring adapter starts at C000, and the RAM can only be excluded in 32K blocks, hence the end value of C800.

If the LANstation is being used with the IBM LAN Support program instead of the LAN Manager 2 stacks, the shared RAM exclusions need to be altered from those stated above. This is because the LAN Support program itself uses another block of high memory. In this case the APRUMB.SYS line in CONFIG.SYS should be:

DEVICE=C:\DOS\APRUMB.SYS /X:C000-C800 /X:D800-DBFF

Here the second exclusion is the block of memory being used by the LAN Support program.

We would like to thank Richard Barriault at Phillips Petroleum for supplying the IBM LAN Support program information.