The Virtex-4 features, such as the programmable IDELAY and built-in FIFO support, simplifythe bridging of a high-speed, PCi-x core to large amounts of DDR-SDRAM memory. Onechallenge is meeting the PCi-x target initial latency specification. PCi-x Protocol Addendum tothe PCI Local Bus Specification Revision 2.0a ([Ref 6]) dictates that when a target signals adata transfer, "the target must do so within 16 clocks of the assertion of FRAME#." PCItermination transactions, such as Split Response/Complete, are commonly used to meet thelatency specifications. This method adds complexity to the design, as well as additional systemlatency. Another solution is to increase the ratio of the memory frequency to the PCi-x busfrequency. However, this solution increases the required power and clock resource usage.
This book is intended as a thorough introduction to both PCI and PCi-x. Is as a “companion” to the specifications. If you’re designing boards or systems using offthe-shelf PCI interface silicon, this book together with the silicon vendor’s data sheets should be sufficient for your needs. On the other hand, if your goal is to design PCI silicon, motherboards or backplanes, you will undoubtedly need to reference the specifications for additional detail.
2.0.12 (May 13th, 2004)
- Flag driver threads with PF_FREEZE to support software suspend.
2.0.11 (May 7th, 2004)
- Avoid split-completion bugs in certain PCi-x chipsets by
breaking up large completion entry DMAs on ADB boundaries.
2.0.10 (April 9th, 2004)
- Return "command timeout" status instead of "selection timeout
status" to the SCSI mid-layer in response to selection timeouts.
While the latter may seem more correct, the mid-layer will not
offline devices suffering from persistent selection timeouts.
This leads to extremely long recovery times for devices that
go missing. Returning command timeout status causes the mid-layer
to enter recovery and eventually offline persistently missing
devices.