Anyway, in practice, without the RAM Limitation Patch (and possibly some other RLoew's patches too, in case the board be relatively new), the limit is about 1.5 GiB RAM, as my list clearly shows (and, by now, I do believe the few reports of > 1.5 GiB RAM without the RAM Limitation Patch may not be really stable, at all, just undertested).
The method you use, @ragnargd, is xRayeR's... It relies on the fact that HIMEMX.EXE hides the XMS memory from windows. Then again, as soon as that RAM is really used, as in filling a XMS Ramdisk, the system will "crash 'n burn", so to say. RLoew has explained it in much more detail in various of his older posts, but, in a nutshell, that's it.