kym@bingvaxu.cc.binghamton.edu (R. Kym Horsell) (10/03/90)
In article <34469@cup.portal.com> Don_A_Corbitt@cup.portal.com writes: >roy@phri.nyu.edu writes: [equality comparison faster than greater] >I haven't seen this in print, but I assume it is because there is extra >delay waiting for carry propagation to set the condition code. XOR can >test all the bits in parallel. I think there is still O(log n) delays for all the bit XOR's to get together into a final result. However, AND-ing together 32 XOR's is a much easier proposition than handling carry lookahead for the same number of bits (assuming greater/less is done using effectively an ALU subtract). The more efficient means of generating less/greater, comparable to the the speed of XOR's for equality, are typically uneconomic to implement in dedicated h/w. -Kym Horsell