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.

Trashbytes wrote on 2024-05-25, 13:44:

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.

Ah.. now it makes sense too, I didn't think of that. Thank you for clarifying. 😁 So therefore it's not possible to install USB on such PC at all, unless maybe if there's some weird adapter or a card that gets additional power from HDD or FDD power cable.

I've never seen a USB card with a Molex adapter but I dont see why it wouldn't be possible, perhaps Evilbay can provide a solution, them Chinese fellas get pretty creative with their angry pixie shenanigans.

Other users here may also have ideas about this.

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 don't see how this potential explanation would apply to the current scenario.

If the single notch on the PCI slot is closer to the front of the case (as opposed to being closer to the slot cover or bracket), it would mean the PCI slot is 5V only.

Adiitionally, a consumer (presumably) PC from 1997 (or even later) having only 3.3V PCI slots rather than 5V ones would not would not make sense either.

OP, Please share the brand and model of the motherboard and some photos of the PCI slots, of a card that works and a of a card that does not fit.

darry wrote on 2024-05-25, 14:47:

I don't see how this potential explanation would apply to the current scenario. […]
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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 don't see how this potential explanation would apply to the current scenario.

If the single notch on the PCI slot is closer to the front of the case (as opposed to being closer to the slot cover or bracket), it would mean the PCI slot is 5V only.

Adiitionally, a consumer (presumably) PC from 1997 (or even later) having only 3.3V PCI slots rather than 5V ones would not would not make sense either.

OP, Please share the brand and model of the motherboard and some photos of the PCI slots, of a card that works and a of a card that does not fit.

/ Shrug I cant think of any other reason a universal card wont go into any PCi slot, by rights it should fit into either types since its designed to do that. And yes you are right I misread the orientation, I read it as front of the slot rather than front of the case.

darry wrote on 2024-05-25, 14:47:

OP, Please share the brand and model of the motherboard and some photos of the PCI slots, of a card that works and a of a card that does not fit.

I took photos of my currently opened PC, the motherboard is pretty much the same in the other two PCs, maybe minor differences, the slots are the same.

These two cards are examples, the black USB PCI card does not fit in, the green network card fits in nicely.

I've had some cards that needed a v-shaped form on the connector in order to be able to slot them down; some cards were simply cut off flat at the bottom of the connector, and were too hard to insert without filing off a bit on each side of the edge connector.

There is also some leeway in spacing between motherboard position and the case wall, sometimes one need to shift the mobo a bit to accommodate cards that are a too close fit.

Rwolf wrote on 2024-05-25, 18:01:

I've had some cards that needed a v-shaped form on the connector

I noticed that some of those non-fitting cards are V-shaped and some are U-shaped, none of them fit in whatsoever. The placement seems exactly fitting so it must be the thickness then. But this is still unclear, are my slots 3.3 of 5 volts? I have received conflicting information on that. If they're 3.3, then I guess I should forget about using USB cards anyway.

I had no idea that PCI slots can vary this much until I started trying those USB cards. Never had any issues with ISA slots yet.

SGM wrote on 2024-05-25, 18:14:

Rwolf wrote on 2024-05-25, 18:01:

I've had some cards that needed a v-shaped form on the connector

I noticed that some of those non-fitting cards are V-shaped and some are U-shaped, none of them fit in whatsoever. The placement seems exactly fitting so it must be the thickness then. But this is still unclear, are my slots 3.3 of 5 volts? I have received conflicting information on that. If they're 3.3, then I guess I should forget about using USB cards anyway.

I had no idea that PCI slots can vary this much until I started trying those USB cards. Never had any issues with ISA slots yet.

All PCI and ISA cards are 1.6mm thick. The slots in the pic are 5V keyed slots. No conflicting info about this, it's the PCI standard as set by Intel.

Trashbytes wrote on 2024-05-25, 14:13:

I've never seen a USB card with a Molex adapter but I dont see why it wouldn't be possible, perhaps Evilbay can provide a solution, them Chinese fellas get pretty creative with their angry pixie shenanigans.

Other users here may also have ideas about this.

Every USB card that can deliver more power than a USB mouse requires has a molex/sata/berg power connector on it. This is extremely common. Not sure how you have not seen one.

kingcake wrote on 2024-05-25, 18:18:

All PCI and ISA cards are 1.6mm thick. The slots in the pic are 5V keyed slots. No conflicting info about this, it's the PCI standard as set by Intel.

I measured all the fitting and non-fitting cards. There was a 0.4mm difference without exception. 😳

Trashbytes wrote on 2024-05-25, 14:13:

I've never seen a USB card with a Molex adapter but I dont see why it wouldn't be possible, perhaps Evilbay can provide a solution, them Chinese fellas get pretty creative with their angry pixie shenanigans.

Other users here may also have ideas about this.

I have seen quite a few powered USB cards, but the ones that had a Molex connector were typically only found in the early days of premium USB 2.0 and combo FireWire controller cards - the juice was needed for better performance and to provide USB and FireWire socket power - and they were quickly replaced by cards that used SATA power connectors, and the Molex ones were relegated to the discount bins or repackaged with Molex-SATA power adapters.

Am not 100% sure the VT6212 is fully 5v tolerant. The NEC D720101 is, has dual voltage buffers and uses 3.3v for all core volts (has one regulator) except the VDD-PCI pin which detects if in 3.3v or 5v PCI slot.
The datasheet for VT6212 does say 5v signal tolerant but lists two core volts, VCC25 @ 2.5v and VCC33 @ 3.3v and lists VCC max of 4.0v, also the card has only one regulator (presumably for the 2.5v) so if in a AT board PCI slot the VCC would be getting 5v not 3.3v...
cannot find info if the buffers are dual voltage....

Horun wrote on 2024-05-25, 18:42:

The datasheet for VT6212 does say 5v signal tolerant but lists two core volts, VCC25 @ 2.5v and VCC33 @ 3.3v and lists VCC max of 4.0v, also the card has only one regulator (presumably for the 2.5v) so if in a AT board PCI slot the VCC would be getting 5v not 3.3v...
cannot find info if the buffers are dual voltage....

PCI provides 3 set of supply voltages: 5V, 3.3V and "the I/O voltage". The VT6212 is obviously meant to be placed directly on the 3.3V rail without any regulator. The term "5V tolerant" means that it can cope with 5V signalling level even if Vcc is just 3.3V. A card with that chip connected to the 3.3V rail will work in any board that is able to supply that rail, even if "the I/O voltage" is 5V. Starting with PCI 2.2, providing 3.3V on the 3.3V rail is mandatory, even in 5V I/O systems. In earlier systems, providing 3.3V was optional if the I/O voltage is 5V. In that case, the 3.3V connections in the PCI slots are unconnected. There will never be 5V on that pins, so the VT6212 will not get fried by an overly high Vcc - but at the same time, the card will not work in systems without 3.3V at the PCI slots, because the VT6212 will get no power at all.

The VT6212 is a good example for a chip that is a perfect fit for a "universal voltage PCI card": The same card works in PCI systems with either 5V or 3.3V signalling voltage, because the VT6212 is able to deal with either 5V or 3.3V signalling - you don't even need to switch anything, because its "high" level and its "low" level at 3.3V supply voltage meet the specifications of both standard TTL (5V PCI) and 3.3V PCI. At the same time, that card also is a good example for a card that fails to work without 3.3V supply voltage on PCI slots.

There are two distinct "era" PCI slots. The ones in the photo are the old style without the relief cut on the rear vertical edge of the slot to clear for 64-bit cards to overhang. It's possible the thickness tolerances on the "old" slots are tighter than the later ones.

Regardless, the 3.3V vs 5V keying is NOT relevant here, that's not the problem.

Edge connectors like that are usually made for 1.6mm +/-10%. Based on that, I would think that 1.8mm is close enough, but the cards that you measured as 1.4mm are too thin. It's possible that both measurements are 0.2mm too thin, which would result in the new cards being way too thick to fit in any PCI slot.

USB 2.0 is too CPU-demanding for socket 7 anyway. I've even had USB 2.0 with one of those VT6212 cards transfer files significantly slower than the onboard USB 1.1 ports with a K6-2/500.

Sometimes the end of the card bracket is too long and is touching the case, this prevents the card from going down completely into the PCI slot.

Ydee wrote on 2024-05-26, 08:37:

Sometimes the end of the card bracket is too long and is touching the case, this prevents the card from going down completely into the PCI slot.

That was never the case with my PC's, I also tried them without the bracket, they just don't go in, as if trying to shove an ISA card into a PCI slot.

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.