Dell PCI slot voltage

Question

Dell specs for PCI slots say this:

3.3 Volt External Operation (some pins 5 Volt
Tolerant); 1.8V internal regulation

Does anyone know what this really means? For example, Optiplex machines have 5V keyed PCI slots, and the specs say "PCI 2.3" and the mysterious comment above. Does this mean that it's possible to put in a 3.3V only card (using an adapter so it will fit), and the card will not be damaged by 5V signals on the motherboard?

I've asked several Dell tech support and sales people, they can't answer this basic question.

-Jeff

dg1261 · Answer

I won't try to interpret what Dell's specs mean--they're often more confusing than helpful. If it's really PCI 2.3, though, I think that means it will accept 3.3V cards only.

Is the Optiplex in your possession, or are you trying to spec something you haven't been able to examine yet? If you can examine it, take a look at the PCI slots. 3.3V slots have the key toward the bracket end of the slot. 5.5V slots have the key toward the opposite end. So either your 3.3V card will fit or it won't.

Bottom line: if the card fits in the slot, it should work.

See also: pinouts.ru/Slots/PCI_pinout.shtml

jbrower888 · Answer

DG1261-

> Is the Optiplex in your possession, or are you trying to spec something you haven't been able to

> examine yet? If you can examine it, take a look at the PCI slots. 3.3V slots have the key toward the

> bracket end of the slot. 5.5V slots have the key toward the opposite end. So either your 3.3V card

> will fit or it won't.

I have personally examined the machine, and as I mentioned, the slots are 5V keyed (notch on inner end). A 3.3V PCI card can fit if I use a Universal adapter, which is like a very small PCI riser card with nothing on it except connectors.

The question is whether Dell truly implemented PCI 2.3 and drove all signals on the PCI bus as 3.3V or whether their spec is a fake and the slot actually drives 5V signals, as the physical keying would indicate. Does anyone know how to get an answer from a motherboard engineer or specialist at Dell who would know the real answer?

So far all Dell tech support and sales people I've talked to are clueless about this. The difference between PCI 2.2 and 2.3 specifications are lost on them -- and worse, they have no idea what their own specs are talking about.

-Jeff

dg1261 · Answer

'the slots are 5V keyed (notch on inner end). A 3.3V PCI card can fit if I use a Universal adapter, which is like a very small PCI riser card with nothing on it except connectors.' Oh. Sorry, I didn't know such a thing existed, so misunderstood your question. (Given that the voltage levels on certain contacts are different depending on the keying, I wouldn't have thought such an adapter possible.)

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Dell PCI slot voltage

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