[rescue] A5000 questions...

Curtis H. Wilbar Jr. rescue at hawkmountain.net
Wed Aug 6 17:12:23 CDT 2003

>From: Dave McGuire <mcguire at neurotica.com>
>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.

Yikes... that's it... 25MHZ !  Oops !

The SS1 had a 20MHZ sbus I think... and in the SS10/20 I think the
sbus is 20mhz when your doing 40mhz mbus, and 25mhz when doing 50mhz
mbus.... correct ?

>   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

big oops there... thanks for catching me Dave...

-- Curt

>Dave McGuire                 "You don't have Vaseline in Canada?"
>St. Petersburg, FL                     -Bill Bradford
>rescue list - http://www.sunhelp.org/mailman/listinfo/rescue

Curtis Wilbar
Hawk Mountain Networks
rescue at hawkmountain.net

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