Silicon Graphics CHALLENGE L, User Manual, Page: 151 / 164

Special VME Considerations
135
allotment would already be saturated. In addition, it is also possible to use a
single 150-watt VMEbus board, providing the remaining VME slots are also
not used.
Special VME Considerations
Generally, there are VME boards or devices that should not be integrated
into the Challenge system. This section provides guidelines for selecting or
designing third-party VME boards.
Caution: Be sure to observe these general rules to avoid possible damage to
the VMEbus and system.
• Devices acting as an A16 VME MASTER will not be able to access
system memory via DMA.
• Devices should require 8-bit interrupt vectors only .
• Devices must not require UAT (unaligned transfers or tri-byte) access
from the Challenge system.
• Devices in Slave mode must not require address modifiers, other than
Supervisory/Nonprivileged data access.
• While in VME Master mode, devices must access only the system
memory that uses Nonprivileged data access or Nonprivileged block
transfers.
• Devices must have the ability to be configured so that their address
range does not conflict with those used by the Challenge. Also, the
device should be able to respond to an address generated by the
system.
• The Challenge system does not support VSBbus boards.
• Be sure to place boards starting in slot 1, or jumper the daisy-chained
signals across the empty slots. Otherwise, breaks occur in the interrupt
acknowledge and bus arbitration schemes.
• Metal face plates or front panels on VME boards may need to be
removed. The plate could prevent the I/O door from properly closing
and possibly damage the I/O bulkhead.