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HDK Technical Reference

Bus

A bus is the hardware used to connect peripheral devices to the computer. SVR5 and SCO OpenServer 5 support a number of industry-standard buses with different performance levels. Various bus standards are compared below.

Supported bus types

 Bus type   Clock speed   Bus width   Bus speed
 (Mhz)      (Mhz)         (bits)      (MB/sec)
 ------------------------------------------------------
 ISA-8      8             8           5 (continuous)
 ISA-16     8             16          10 (continuous)
 EISA       8             32          32 (burst)
 MCA        10            32          40 (burst)
 PCI        33            32          132 (continuous)
 VESA       33            32          132 (continuous)

DDI coding

Use the facilities discussed in ``Autoconfiguration'' to detect and configure devices on any supported bus type. SCO SVR5 1 and 2 and SVR5 support bus-independent APIs for access to for this purpose. bus-dependent configuration space. Specifically:

ODDI coding

On SCO OpenServer 5, separate functions are defined for accessing each supported bus type. These include:


archtobus(D3oddi)
extract bus type from architecture; used for ISA, EISA, and MCA architectures.

pci_buspresent(D3oddi)
determine the presence of a PCI bus.

Because a system can have a PCI bus in combination with any other bus type, driver writers must use both functions in drivers that support both PCI and non-PCI cards.


© 2005 The SCO Group, Inc. All rights reserved.
OpenServer 6 and UnixWare (SVR5) HDK - June 2005