On Friday 17 June 2005 10:14 am, Mike Williams wrote: > Are you sure you've got that the right way round? > I though 5V PCI cards have a second slot in the connector, 3.3V's do not. > So you can't put a 3.3V card in a 5V slot, but can put a 5V card in a 3.3V > slot. 3.3V cards that can handle 5V are the exception, and to add more > confusion, there are probably boards with 3.3V style connectors, than can > supply 5V if required too. Fun, eh?
I ran into this problem with a Rvia TNT graphics card. My understanding is that there are actually two notches/gaps in the slot. One for 3.3V, and one for 5V. If a card handles either then it will have two notches. If it handles one or the other it will have the appropriate gap. Some motherboards supply 3.3V, some supply 5V, and some supply both. I happened to have a TNT which wouldn't fit into a motherboard. I swapped it with another card which had two notches that was in another motherboard which was compatible with the single-notched board. The freed-up TNT would then work in the newer board. I'm sure somebody can explain all of this better than I can, but that was when I first learned about the two voltage conventions. I think one of the boards I was working with was from a Dell, which might explain the limitations on compatiblity. The name-brands tend to save $10 on the motherboard by using less versatile models, since they have full control over all the other stuff going into the system. Retail boards tend to be more versatile, since they cater to a market where people are likely to have a load of old cards they plan on recycling. The same applies to power supplies - where you or I would use a 400W supply Dell will use an cheap 250W supply and find the one model of motherboard on the market which is actually compatible with it. With their volumes they can more easily afford to buy 500 different models of parts and spend 500 hours figuring out which ones work together best than to spend an extra $10 per unit getting parts with sufficient tolerances that it doesn't matter. (Have I mentioned I don't like name-brand consumer boxes?)
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