Just finished a build using a Silverstone GRANDIA GD04. Cable management was more difficult than I thought it would be. I've got one of my PSU cables (meshed) running underneath (near the air intake, but under the PCB) my 4890. I know the 4890 gets very hot and when the computer is running and the PCB is very hot to the touch. My concern is that I may melt or damage the PSU line running underneath the card? Is this possible or am I worried about nothing? Thank you
If the PCB really gets that hot, and is touching the cable - personally I'd move the cable. The wires wont get damaged as you need something stupid to melt steel or copper or whatever is in them but you don't want the sleeving to melt or warp shape etc. Can you not tie it down so it's not touching, or just move it out from the PCB at all?
Ideally, you don't want wiring near anything that could get hot enough to melt either the plastic mesh, or worse, the vinyl wiring insulation, which would expose the wiring and likely cause a short. As a 4890 and 4850 owner, neither of my cards has ever gotten hot enough to do that, even during quite lengthy gaming sessions.
Coincidentally, my 4850 system ran into a very similar problem...
The PSU of my 4850 system has a few relatively short cables. After installing it in a bottom-mount case (Antec 300), the 4+4-pin CPU power cable was too short to run behind and back over the top of the motherboard, despite the hole I drilled out for it. So, I had a choice - run it over the 4850 (where it could easily come in contact with the cooler's heatpipes), or run it under the card along the back of the motherboard. I chose to run it under the rear (right behind the PCI-E slot) of the card, right up along the back panel. I too was worried this might not be safe, so I wrapped that cable with yellow electrical tape. I figured a bright color would make detection of any problem easily noticeable, and none have come to pass. It's been working fine like that for over a year.
Your 4890 is unlikely to hit 100C, it will likely stay far below there. Since there is no active heatpump in the system, and therefore nothing can get hotter than the source, no part of your card should hit or exceed 100C which means it will have a pretty hard time melting the insulation of anything, especially sleeved cables with high temp insulation on them, it wont be a problem.