e6400 nvidia: copper shim

site/docs/hardware/e6400.md

@@ -118,6 +118,37 @@ see [../install/ich9utils.md](../install/ich9utils.md)*
 Issues pertaining to Nvidia GPU variants
 ========================================
 
+Copper shim for GPU cooling
+---------------------------
+
+NOTE: this section does *not* apply to XFR or ATG variants of E6400, which have
+a much beefier heatsink by default.
+
+The *default* heatsink in Nvidia variants of E6400 (regular model) has thermal
+paste for the CPU, and a thermal *pad* for the GPU. This pad is woefully
+inadequate, but replacing it with *paste* is a bad idea, because of the gap
+there would be between heatsink plate and GPU die.
+
+A solution for this would be to use a *copper shim*, with paste on each side,
+to replace the thermal pad.
+
+This eBay seller seems to make and sell a lot of copper shims, specifically
+for E6400:
+
+<https://www.ebay.com/itm/282033838969>
+
+If the listing ends, please [contact the Libreboot project](../../contact.md)
+so that this link can be replaced or (if a replacement link is no longer
+available) removed.
+
+If you buy one of those, could you measure it? Tell Libreboot the dimensions.
+Get in touch with us. It would be nice to know precise specs, but that seller
+provides what you need. If you find similar listings elsewhere, please also
+let us know.
+
+The shim will greatly reduce GPU temperatures, and probably improve performance
+due to less GPU throttling as a result of heat.
+
 Nouveau(in Linux) currently broken
 ----------------------------------