(no commit message)

diff --git a/openpower/sv/biginteger.mdwn b/openpower/sv/biginteger.mdwn
index ee2694751c2e2e5f6e581ff4e6ed33301abd83c3..bfd566cfd06b1305d27e0fdf17cef7a5cc733593 100644 (file)
--- a/openpower/sv/biginteger.mdwn
+++ b/openpower/sv/biginteger.mdwn
@@ -41,6 +41,15 @@ ALU.
 
 ## Multiply
 
+Long-multiply, assuming an O(N^2) algorithm, is performed by summing
+NxN separate smaller multiplications together.  Karatsuba's algorithm
+reduces the number of small multiplies at the expense of increasing
+the number of additions.  Some algorithms follow the Vedic Multiply
+pattern by grouping together all multiplies of the same magnitude/power
+(same column) whilst others perform row-based multiplication: a single
+digit of B multiplies the entirety of A, summed a row at a time. This
+algorithm is the basis of the analysis below (Knuth's Algorithm M).
+
 Multiply is tricky: 64 bit operands actually produce a 128-bit result,
 which clearly cannot fit into an orthogonal register file.
 Most Scalar RISC ISAs have separate `mul-low-half` and `mul-hi-half`