[GTALUG] Graphics cards - - - too much 'joy'

[D. Hugh Redelmeier]

| From: o1bigtenor via talk <talk at gtalug.org>

| On Fri, Dec 6, 2019 at 7:50 AM D. Hugh Redelmeier via talk
| <talk at gtalug.org> wrote:

| > <https://allpinouts.org/pinouts/connectors/power_supply/pci-express-pcie-6pin-power/>
| > <https://allpinouts.org/pinouts/connectors/power_supply/pci-express-pcie-8pin-power/>
| >
| > Or better (but look way down, from "6 Pin PCI Express (PCIe) Power
| > Cable Connector" on):
| >
| > <https://www.moddiy.com/pages/Power-Supply-Connectors-and-Pinouts.html>
| >
| > The original 6 pins are all assigned 12v or ground.  The extra pins in
| > the 8 pin connector are just grounds.  All seem to be connected.
| 
| The top row is the issue.

I'm not 100% sure how the pins are numbered and I'm not 100% sure what the 
"top" is.

| The top row are all labelled as ground (IIRC the bottom row are all 12 V.

Careful.  Both of the extra two pins are ground.  So if the bottom row of the six 
pin connector were all 12V, that would NOT be true of the 8-pin connector.

| AIUI
| that is the newer style of connector. In the past there was not uncommonly
| used a cable w an 8 pin on one end and a 6 + 2 on the other. The 8 pin then on
| the left hand side had both top and bottom pins labelled as ground so it makes
| sense that one ground line was omitted - - - - especially as the predominant
| graphics boards at the time used 2 - 6 pin connectors.

Why does it make sense to omit a ground line?  If it is specified to be 
ground, it ought to be supplied as ground.  As I read it, the power supply 
must supply ground on all the ground pins but the video card is free to 
not use some of them.

If one of the pins from the power supply isn't connected, then the
cable is defective.

Note: it might be connected within the connector itself via an
internal jumper.