There are any places where it said that the page size in the GT200 series is 512KB (e.g. Here)
I’m studying the performance of the TLB levels in the GT200 family and I would know if someone has checked this question because i have made any cases and always obtained 128KB of page size.
I don’t know if you’ve made any progress but I’m starting to suspect that the page size depends on the number of memory banks. I’m getting what look like TLB effects which are different on the GTX260 compared to the GTX280. If you have a GT200 with only 2 memory banks (such as the GT220 or GT240) maybe it would have a 128KB page size?