The original post said "8I915ME-RH" not "8I915ME-GL".
Gigabyte dont list a "RH" version, it may be a regional designation; either way the chipset allows Core2 Duo and Quad cpus, so will probably work.
For the cost of a cheap 2nd hand chip from Ali Express, it is worth trying.
Where did you see that allows core 2 quad, it has n/a in the cpu supported table for core 2 duo, that means not supported.
Sorry, my mistake; usually manfs dont list cpu ranges that dont work, only specific models - usually for power reasons.
Having said that, according the the Intel spec sheet, the chipset itself (Intel 915) DOES allow Core2 Duo and Quad; it may be that Gigabyte havent included the microcode needed to identify them; or that the boards power circuits are so pared down, that it is incapable of supplying the juice needed.
If it is the later reason, a Xeon may still work, as they have versions with a lower power requirement than the Core 2 equivalent.