Microcode, which is a no-go for modern designs

dwight dkelvey at hotmail.com
Fri Jan 4 09:08:05 CST 2019


May ability to understand these papers is somewhat limited. If I understand correctly the following.
Most divide routines that I've seen allow the remainder to be 1,0,-1 relative to the normal remainder. The answer will converge as the error of the remainder never leaves this range.
In the case of the pentium, the remainder is 2,1,0,-1,-2. This allows the division to converge on the answer quicker. The error was that if the remainder was right on one edge it would eventually fall of the edge and not converge. From the paper, that would be the 5 1's in a row, of the divisor.
At least that is my understanding. It is to early in the morning for me.
Dwight

________________________________
From: Eric Smith <spacewar at gmail.com>
Sent: Thursday, January 3, 2019 11:55 PM
To: dwight; General Discussion: On-Topic and Off-Topic Posts
Subject: Re: Microcode, which is a no-go for modern designs

And the original analysis paper, "It Takes Six Ones to Reach a Flaw":
http://www.acsel-lab.com/arithmetic/arith12/papers/ARITH12_Coe.pdf



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