3 ms·

How do people find hacks like this? Looking at the board, that resistor is one among tons of components.

by leoh 14y ago

ajross 14y ago
Mostly like inside or semi-inside info. Obviously anyone with a schematic and datasheet at any of the dozens of OEMs will be able to figure this out. But even without docs there were probably bunches of reference boards shipped out to integrators. It's not hard to visually diff a "Quadro" from a "Tesla" version of the same board. What I'm more surprised by is the fact that this was done by external resistors at all. Almost all chip configuration like this these days is done with on-die fuses that can't be hacked.
malloc2x 14y ago
If you read some of the comments, essentially: a) looking for resistors that could be placed in multiple positions on the board and b) following the traces from the resistors: going to GPU? probably not what you want. Going to PCIE interface? Probably correct.
memset 14y ago
He actually describes it in the thread, a little farther down: "No, no schematic, what I did was look for resistors that looked like they had an alternative position, have a look at the photos and you will see what I mean. Any that I suspected of being a strap I used a meter to check if the resistor was connected to ground of 3.3V directly, and looked where the general traces were going in the area. If they went towards the GPU and connected to one of the rails it was a pretty good bet that it was a hard strap." http://www.eevblog.com/forum/projects/hacking-nvidia-cards-into-their-professional-counterparts/msg203225/?PHPSESSID=f88387c520550af1e0508d8687b41928#msg203225 http://www.eevblog.com/forum/projects/hacking-nvidia-cards-i...
- pdmccormick 14y ago
  I once saw a networking IC that had a key strap-in pin multiplexed with an indicator LED, so if you wanted to change the brightness of the LED by varying the resistor value, watch out because you'll change the device behaviour! Good times...

How do people find hacks like this? Looking at the board, that resistor is one among tons of components.

by leoh 14y ago

How do people find hacks like this? Looking at the board, that resistor is one among tons of components.

Mostly like inside or semi-inside info. Obviously anyone with a schematic and datasheet at any of the dozens of OEMs will be able to figure this out. But even without docs there were probably bunches of reference boards shipped out to integrators. It's not hard to visually diff a "Quadro" from a "Tesla" version of the same board. What I'm more surprised by is the fact that this was done by external resistors at all. Almost all chip configuration like this these days is done with on-die fuses that can't be hacked.

malloc2x 14y ago

If you read some of the comments, essentially: a) looking for resistors that could be placed in multiple positions on the board and b) following the traces from the resistors: going to GPU? probably not what you want. Going to PCIE interface? Probably correct.

memset 14y ago

He actually describes it in the thread, a little farther down: "No, no schematic, what I did was look for resistors that looked like they had an alternative position, have a look at the photos and you will see what I mean. Any that I suspected of being a strap I used a meter to check if the resistor was connected to ground of 3.3V directly, and looked where the general traces were going in the area. If they went towards the GPU and connected to one of the rails it was a pretty good bet that it was a hard strap." http://www.eevblog.com/forum/projects/hacking-nvidia-cards-into-their-professional-counterparts/msg203225/?PHPSESSID=f88387c520550af1e0508d8687b41928#msg203225 http://www.eevblog.com/forum/projects/hacking-nvidia-cards-i...

pdmccormick 14y ago
I once saw a networking IC that had a key strap-in pin multiplexed with an indicator LED, so if you wanted to change the brightness of the LED by varying the resistor value, watch out because you'll change the device behaviour! Good times...