add rename description

diff --git a/3d_gpu/microarchitecture.mdwn b/3d_gpu/microarchitecture.mdwn
index 7975be84c063dc5e0eb71d69137156f9bd46ed2f..360970645f3f20e62e1d9825d81bba8ae77846d8 100644 (file)
--- a/3d_gpu/microarchitecture.mdwn
+++ b/3d_gpu/microarchitecture.mdwn
@@ -402,6 +402,21 @@ and there are several of them:
 
 ## Register Renaming
 
+There are several potential well-known schemes for register-renaming:
+*none of them will be used here*.  The scheme below is a new form of
+renaming that is a topologically and functionally **direct** equivalent
+of the Tomasulo Algorithm with a Reorder Buffer, that came from the
+"Register Alias Table" concept that is better suited to Scoreboards.
+It works by flattening out Reservation Stations to one per FU (requiring
+more FUs as a result).  On top of this the function normally carried
+out by "tags" of the RAT table may be merged-morphed into the role
+carried out by the ROB Destination Register CAM which may be merged-morphed
+into a single vector (per register) of 1-bit mutually-exclusive "CAMs"
+that are added, very simply, to the FU-Register Dependency Matrix.
+
+In this way, exactly as in the Tomasulo Algorithm, there is absolutely no
+need whatsoever for a separate PRF-ARF scheme.  The PRF *is* the ARF.
+
 Register-renaming will be done with a single extra mutually-exclusive bit
 in the FUxReg Dependency Matrix, which may be set on only one FU (per register).
 This bit indicates which of the FUs has the **most recent** destination