video window size & AGP aperture size ? ? ?

While tweaking my GeForce2 MX 400 64mb chip I found two settings in bios that have to do with my AGP card. One is "onchip video window size" and the other is "AGP aperture size"

In bios found settings for on chip video window size 32/64 and AGP aperture size 32/64

I decided to change these around a bit to see what would happen.

onchip video window / agp aperture size

at 64/64 score 4504
at 32/64 score 4503
at 32/32 score 4511 and 4591
at 64/32 score 4491 4489 4493

Don't know what's going on here. If you look changing the onchip video window size made no difference at all. Maybe someone can explain to me what that setting is so I can better understand it, I have no idea what the onchip video window size is or what it should be set to for my 64mb GeForce 2mx 400 card.
You also notice that changing the AGP aperture size did make a small difference but nothing huge. The larger aperture size seemed to give higher scores.

So If someone can give a good explanation or knows where I can read one It would be greatly appreciated.

The AGP aperture is an area of system RAM reserved for use by the AGP card for storing textures if it needs to. The RAM is available for use by the system as normal if not used by the graphics card. This feature was of importance for graphics cards in the past, when cards typically only had 4MB or 8MB of onboard memory. However, as most modern AGP graphics cards now have 32MB or 64MB of SDRAM, the setting is now of much less consequence. It is generally advised to set the AGP aperture to half the system RAM - i.e. set to 32MB with 64MB of RAM. However, this advice predates the use of systems with more than 64MB of RAM and large graphics cards memories. In most cases you are unlikely to need to set the AGP aperture at more than 32MB, although in order to complete some of the artificial 3DMark200x benchmarks you may need to use an aperture of 64MB to hold all the textures.