From d35e3011030538db2b48850c811076a0da934149 Mon Sep 17 00:00:00 2001
From: Rikard Nordgren <hrn@posteo.net>
Date: Mon, 26 Jan 2026 19:16:00 +0100
Subject: [PATCH] Update mov_r_FAC1_VAR

---
 STATUS.md                                | 2 +-
 src/basic/math_mov/bbd0.mov_r_FAC1_VAR.s | 9 +++++++--
 tools/similarity.c                       | 2 +-
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/STATUS.md b/STATUS.md
index ccb1b8b4..99c892ad 100644
--- a/STATUS.md
+++ b/STATUS.md
@@ -225,7 +225,7 @@ Floating point mathematical routines - not official, but well known and broadly
 | `$BBA6`   | `get_FAC1_via_INDEX`   | DONE     |                                                    |
 | `$BBC7`   | `mov_r_FAC1_TMP2`      | PARTIAL  | not fully tested yet                               |
 | `$BBCA`   | `mov_r_FAC1_TMP1`      | PARTIAL  | not fully tested yet                               |
-| `$BBD0`   | `mov_r_FAC1_VAR`       | PARTIAL  | not fully tested yet                               |
+| `$BBD0`   | `mov_r_FAC1_VAR`       | DONE     | From the Microsoft BASIC, original name: MOVVF     |
 | `$BBD4`   | `mov_r_FAC1_MEM`       | DONE     | From the Microsoft BASIC, original name: MOVMF     |
 | `$BBFC`   | `mov_FAC2_FAC1`        | DONE     | From the Microsoft BASIC, original name: MOVFA     |
 | `$BC0C`   | `mov_r_FAC1_FAC2`      | DONE     | From the Microsoft BASIC, original name: MOVAF     |
diff --git a/src/basic/math_mov/bbd0.mov_r_FAC1_VAR.s b/src/basic/math_mov/bbd0.mov_r_FAC1_VAR.s
index 9de76027..6330dd3b 100644
--- a/src/basic/math_mov/bbd0.mov_r_FAC1_VAR.s
+++ b/src/basic/math_mov/bbd0.mov_r_FAC1_VAR.s
@@ -3,9 +3,14 @@
 ;; #LAYOUT# *   BASIC_0 #TAKE
 ;; #LAYOUT# *   *       #IGNORE
 
-;
+
+; This file is under the MIT license, it contains code released by Microsoft Corporation.
+; See LICENSE for more information.
+
 ; Math package - move FAC1 (rounds) to memory variable
 ;
+; This is verified to be identical to the original Microsoft implementation where it was named MOVVF.
+;
 ; Input:
 ; - FORPNT ($49/$4A) - variable address
 ;
@@ -15,7 +20,7 @@
 
 mov_r_FAC1_VAR:
 
-	ldy #FORPNT+1
 	ldx #FORPNT+0
+	ldy #FORPNT+1
 
 	; FALLTROUGH to mov_r_FAC1_MEM
diff --git a/tools/similarity.c b/tools/similarity.c
index 5b62e59b..2108dd72 100644
--- a/tools/similarity.c
+++ b/tools/similarity.c
@@ -24,7 +24,7 @@ int phase_mask[MAX_SIZE+MAX_SIZE];
 // Pairs of start, end memory addresses of known exact similarity with the open source Microsoft BASIC
 unsigned short microsoft_basic_chunks[NUM_CHUNKS * 2] = {
     0xB849, 0xB84F,
-    0xBBD4, 0xBC1A
+    0xBBD0, 0xBC1A
 };