The mystery number '63' in the context of demand paging

I am running a code that mimics demand paging system here are some of the parameters:

Page size = 4096 bits
Processor = 32 bits
Number of page frames = (variable)

I run my code with a fifo or random page replacement algorithm with number of page frames set to 100. My disk read/ write ends at 63.

Then when I changed the Processor size to 32 bits - this boundary moves to 16.

The latter case, I understand. If the page frame count is more than the possible page table entries, (2^4) ther开发者_高级运维e is no need for evictions.

But I don't understand why in the former case, where the page table entries go up to 2^20, the disk read/write stops at 63 with both page replacement algorithms.

What is this mystery 63 number? Any idea where this may be coming from? Thank you.

The reference string had only 63 pages -- now that I have gotten some sleep...