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.

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