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Re: PRSNT Signals


1 - PCI Slots aren't plentiful system resources so I'd look at using a Drive
Power cable before using a PCI Slot just for power. There wouldn't be any
other reason for this not to be acceptable practice.

2 - PRSNT Pins: Some system resources can use PRSNT pins to detect if a device
is in the slot and not provide PCI Clock and other resources if a card is not
detected. The pins should be tied to indicate the power your board would draw.
In your case the only reason you would only want to make sure your card is
detected via PRSNT pins is if the host system would choose not to power an
unoccupied slot.

3 - TDO should be connected to TDI to keep chain going, but no one really uses
connector JTAG yet.

- Cary

----- Original Message -----
From: peter.ross <peter.ross@imshq.ftech.co.uk>
To: <pci-sig@znyx.com>
Sent: Tuesday, February 15, 2000 4:50 AM
Subject: PRSNT Signals

We are currently developing a PCI expansion card product. This will require
the use of two slots, although only one is intended to be connected to the
bus. The second card will take only power from the motherboard connector.

Some questions on this:

1. Is this an acceptable practice?
2. According to the V2.1 specification, the PRSNT signals are used for two
purposes: to indicate the power requirements of the board; and to indicate
that there is a board present. Does this mean that the host computer would
attempt to configure the card in this slot, given that at least one of the
PRSNT signals was tied down? Would this cause a problem?
3. I assume that TDO would have to be connected to TDI ?


Peter Ross