[rescue] A5000 questions...

Dave McGuire mcguire at neurotica.com
Wed Aug 6 16:29:28 CDT 2003

On Wednesday, August 6, 2003, at 05:16 PM, Curtis H. Wilbar Jr. wrote:
>> OK, since the document for the 501-5202 mentions the A5k, I guess it
>> works.  Here, I'd been under the impression that Sun's wierd 25MByte
>> existed for sbus.
> I think that is the bandwidth for an SBUS card....  that is independent
> of the bandwidth of the interface is supports (although it is a choking
> point for external interfaces with higher bandwidth than the sbus).

   Uhhhhhhhhh, NO.  Sbus is usually clocked at 25MHz and it's four bytes 
wide, making it about the equivalent in performance to baseline PCI.  
The faster (33MHz) baseline PCI clock advantage is eaten up by the way 
sbus starts and stops transfers...with sbus, one transfer can start on 
the very next cycle after the last transfer ends, but with PCI there 
are intervening arbitration cycles.

   First-generation PCI, Sbus, and DEC's TurboChannel are pretty much 
equivalent in performance, if my tired brain is remembering all the 
numbers correctly.


Dave McGuire                 "You don't have Vaseline in Canada?"
St. Petersburg, FL                     -Bill Bradford

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