spktu
Member level 5
5v add in boards for pci slot
In the PCI Local Bus Technical Summary **broken link removed**
it is said, that :
"The PCI specification defines two types of connectors that may be implemented at the system board level: One for systems that implement 5 Volt signaling levels, and one for systems that implement 3.3 Volt signaling levels.
Three types of add-in boards may be implemented: "5 Volt add-in boards" include a key notch in pin positions 50 and 51 to allow them to be plugged only into 5 Volt system connectors. "3.3 Volt add-in boards" include a key notch in pin positions 12 and 13 to allow them to be plugged only into 3.3 Volt system connectors. "Universal add-in boards" include both key notches to allow them to be plugged into either 5 Volt or 3.3 Volt system connectors. Universal boards must be able to adapt to operation at either signaling level. "
I checked a PCI slot ( on a common P4 motherboard ) intended for "5 Volt add-in boards".
It really had +5V on appropriate pins as should have been in a 5V System Environment.
BUT ALL I/O PINS IN THAT SLOT HAD 3.3Volts LEVELS!!!
Questions:
1). Did anybody see PCI slot intended for "3.3 Volt add-in boards" on common P4 motherboards?
Why are they ever needed if even PCI slot intended for "5 Volt add-in boards" have all I/O pins at 3.3 Volts?
2). If I design a PCI controller with a non-5Volts tolerant FPGA, than shall I put level convertors from 5V->3.3V?
In the PCI Local Bus Technical Summary **broken link removed**
it is said, that :
"The PCI specification defines two types of connectors that may be implemented at the system board level: One for systems that implement 5 Volt signaling levels, and one for systems that implement 3.3 Volt signaling levels.
Three types of add-in boards may be implemented: "5 Volt add-in boards" include a key notch in pin positions 50 and 51 to allow them to be plugged only into 5 Volt system connectors. "3.3 Volt add-in boards" include a key notch in pin positions 12 and 13 to allow them to be plugged only into 3.3 Volt system connectors. "Universal add-in boards" include both key notches to allow them to be plugged into either 5 Volt or 3.3 Volt system connectors. Universal boards must be able to adapt to operation at either signaling level. "
I checked a PCI slot ( on a common P4 motherboard ) intended for "5 Volt add-in boards".
It really had +5V on appropriate pins as should have been in a 5V System Environment.
BUT ALL I/O PINS IN THAT SLOT HAD 3.3Volts LEVELS!!!
Questions:
1). Did anybody see PCI slot intended for "3.3 Volt add-in boards" on common P4 motherboards?
Why are they ever needed if even PCI slot intended for "5 Volt add-in boards" have all I/O pins at 3.3 Volts?
2). If I design a PCI controller with a non-5Volts tolerant FPGA, than shall I put level convertors from 5V->3.3V?