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diff --git a/openpower/sv/remap.mdwn b/openpower/sv/remap.mdwn
index 1d10b417487e79c7bb1940cf0884b3e3c88db3db..9e832390b0c92d0023495503c5b02ac18291c0df 100644 (file)
--- a/openpower/sv/remap.mdwn
+++ b/openpower/sv/remap.mdwn
@@ -221,7 +221,7 @@ Form: SVM-Form SV "Matrix" Form (see [[isatables/fields.text]])
 
 Fields:
 
-* **SVxd** - SV REMAP "xdim"
+* **SVxd** - SV REMAP "xdim" (SVGPR>>1 for Indexed REMAP)
 * **SVyd** - SV REMAP "ydim"
 * **SVzd** - SV REMAP "zdim"
 * **SVRM** - SV REMAP Mode (0b00000 for Matrix, 0b00001 for FFT etc.)
@@ -250,6 +250,11 @@ Fields:
 Examples showing how all of these Modes operate exists in the online
 [SVP64 unit tests](https://git.libre-soc.org/?p=openpower-isa.git;a=tree;f=src/openpower/decoder/isa;hb=HEAD)
 
+In Indexed Mode, there are only 5 bits available to specify the GPR
+to use, out of 128 GPRs (7 bit numbering).  Therefore, only the top
+5 bits are given in the `SVxd` field: the bottom two implicit bits
+will be zero (`SVxd || 0b00`).
+
 `svshape` has *limited applicability* due to being a 32-bit instruction.
 The full capability of SVSHAPE SPRs may be accessed by directly writing
 to SVSHAPE0-3 with `mtspr`. Circumstances include Matrices with dimensions