(no commit message)

diff --git a/3d_gpu/architecture/dynamic_simd/add.mdwn b/3d_gpu/architecture/dynamic_simd/add.mdwn
index 250c4723ea13ddb289699256470db8c8f7673cca..5ed776a302783f0a830a6a35629344b9381a5009 100644 (file)
--- a/3d_gpu/architecture/dynamic_simd/add.mdwn
+++ b/3d_gpu/architecture/dynamic_simd/add.mdwn
@@ -50,9 +50,12 @@ carry-out-cascade example:
     partition:      1    0    0    1      (4 bits)
     actual   : <--->|<------------>|<---> actual numbers
     carryotmp: o4   o3   o2   o1   o0     (5 bits)
-    cascade  : |    |    x    x    |
-             : v    v    x    x    v
+    cascade  : |    |    x    x    |      o2 and o1 ignored
     carry-out: o4   \->  -->  o3   o0     (5 bits)
 
-
+because the partitions subdivide the 5-wide input into 8-24-8, o4 is already
+in "both" the MSB-and-LSB position for the top 8-bit result; o3 is the
+carry-out for the 24-bit result and must be cascaded down to the *beginning*
+of the 24-bit partitioned result (the LSB), and o0, like o4, is already in
+position because the partition is only 1 wide.