From 8e9117eb864a6ffc66ced72f5bb168ee0b1cbf76 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Sat, 28 Dec 2024 03:40:59 +0100
Subject: [PATCH] [KERNAL] improve entropy_get by including scanline as source
 (#379)

---
 kernal/drivers/x16/entropy.s | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernal/drivers/x16/entropy.s b/kernal/drivers/x16/entropy.s
index aaacf493..0c2692a6 100644
--- a/kernal/drivers/x16/entropy.s
+++ b/kernal/drivers/x16/entropy.s
@@ -32,9 +32,9 @@ entropy_init:
 ;            x    random value
 ;            y    random value
 ;---------------------------------------------------------------
-; We only have two bytes of entropy, so we return the XOR in the
-; third byte:
-;            a    timer lo
+; We only have two bytes of entropy from the timer, so we
+; also return the XOR with the current scan line as 3rd byte
+;            a    timer lo eor rotated scanline
 ;            x    timer hi
 ;            y    timer lo + timer hi
 ; Timer lo is read twice, so there will be some difference.
@@ -43,5 +43,7 @@ entropy_get:
 	tax
 	adc d1t1l ; feed in .C from user
 	tay
-	lda d1t1l
+	lda VERA_IRQ_LINE_L
+	rol
+	eor d1t1l
 	rts