RAM 6.0 BUX II Series Betriebsanweisung PDF herunterladen (Seite 36)

VxWorks

Hardware Considerations Guide, 6.0

transactions on the PCI bus. The result was that every device driver for devices

which might be placed on the PCI bus would not work, because they use the full

PCI capabilities and transactions of less than 64-bit size. So, no PCI devices would

work for any system based on that host bridge with standard drivers, and all

device drivers on such a system must be custom versions, resulting in greater

software costs.

Another example of this problem on a device was an early version of a specific

SCSI-2 device. In an earlier version of VxWorks, the Wind River SCSI driver legally

asserted the attention line during the command phase. The microcode used in the

device was incompatible with this, and caused the entire bus to become unusable.

Although Wind River has modified the SCSI driver in a way which overcomes this

particular difficulty, this example does illustrate the consequences of hardware

which does not fully conform to industry standards.

There are many devices which exhibit this problem. In each case, the solution

requires either additional expense in software development, more than making up

for the savings of the reduced part, or reduced system capability and/or

performance.

The resolution is to design using hardware which fully complies with the required

standards.

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RAM 6.0 BUX II Series Betriebsanweisung Seite 36