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Valued Contributor III
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Use of QuickSwitches on MAXII and some other PCI Compliant Dev Kits (Stratix, etc.)

Can someone explain me why there are 5V to 3V QuickSwitches on the 50some PCI Bus Signals/Lines on the MAXII Development Board Kit while this CPLD (EPM1270) is equipped with PCI 3.3V Clamp Diodes ???  

 

I saw this is the case too with at least the Stratix Development Board !  

(see the Schematics at the end of this document: https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/ds/ds_stratix_pci_bd.pdf )  

 

This seems redundant for me.  

Unless I'm missing something ??? :confused:  

 

Since the PCI 3.3V Clamp Diodes, why not connect the 5V Bus Signals/Lines directly to PCI pins of the EPM1270 ???  

 

Thanks for your lights on this matter because we're about to design a PCB supporting the 5V PCI Bus based on this MAXII Device...
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