*pop...

mkarcher wrote on 2024-05-26, 12:10:

I know that this thread is about badly manufactured cards using a PCB that's too thick. While I didn't observe this on PCI cards […]
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Trashbytes wrote on 2024-05-25, 13:44:

Perhaps the card is designed that way because it doesn't support 3.3v only PCI slots, universal is meant to signify that it supports either but that's not always the case and being a USB card it likely wants a 5v slot to provide +5V to USB peripherals which a 3.3v only slot cant do.

I know that this thread is about badly manufactured cards using a PCB that's too thick. While I didn't observe this on PCI cards yet, I've seen a set of overly thick 30-pin SIMMs, so I know that components using overly thick PCBs are a thing.

Nevertheless, I want to point out that a slot keyed for "3.3V" still has its 5V supply. A slot with the 3.3V key does not mean that there are no 5V supply pins on the slot. The 3.3V key means that the system this slot belongs to is specified to never have more than 3.3V on the signal lines. The two practical implications for PCI cards are: First, you may use 3.3V-only logic that is not 5V tolerant on a card that is keyed as 3.3V only. Second, a card keyed as "3.3V only" must never output levels above 3.3V on the PCI signal lines.

A standard PCI slot has

• 8 pins of +5V, independent of the keying
• 12 pins of +3.3V, independent of the keying. Before PCI 2.2, these pins were allowed to be not connected to anything in 5V PCI slots.
• 5 pins of at the I/O voltage, that is 5V on 5V slots and 3.3V on 3.3V slots.
• 17 ground pins on "universal" boards, 21 ground pins on 3.3V or 5V boards. The second notch of a universal board replaces 4 ground pins. 33-Mhz-only systems may use the 66-MHz indication pin as another ground pin, increasing the number to 18/22.

As the 8 pins of +5V not optional in any PCI revision, there should be no need for a Molex connector to get +5V. PCI boards may consume up to 25W, but are "recommended" to not consume more than 10W in default configuration. As 4 ports of USB 2.0 are specified to consume 10W at max, and the supply of the controller chip is negligible in comparison, the amount of power available on a PCI slot should also suffice for any 4-port USB 2.0 controller card.

I didn't know this, I was always under the assumption that 3.3v only PCI cant supply 5v to cards that are keyed only for that voltage and vise a versa, early PCI was damn weird