From: Maxwell Beck <max@rastertail.net>
Date: Mon, 30 Dec 2024 21:21:14 +0000 (-0600)
Subject: Tighten drive lookahead, improve track stepping
X-Git-Url: https://rastertail.net/scm/?a=commitdiff_plain;h=2a3984933e9b39cd37a136dd2a95645bff0d3774;p=pico1541.git

Tighten drive lookahead, improve track stepping
---

diff --git a/src/drive.c b/src/drive.c
index cc85635..64b765a 100644
--- a/src/drive.c
+++ b/src/drive.c
@@ -55,7 +55,7 @@ void drive_step_up(drive_t *drive) {
 	if (drive->track < 39 && drive->halftrack == 0) {
 		drive->image_ptr += SECTORS_PER_TRACK[drive->track] << 8;
 		drive->track += 1;
-		drive->sector = drive->sector % SECTORS_PER_TRACK[drive->track];
+		drive->sector = drive->sector * SECTORS_PER_TRACK[drive->track] / SECTORS_PER_TRACK[drive->track - 1];
 	}
 }
 
@@ -64,7 +64,7 @@ void drive_step_down(drive_t *drive) {
 	if (drive->track > 0 && drive->halftrack == 0) {
 		drive->image_ptr -= SECTORS_PER_TRACK[drive->track - 1] << 8;
 		drive->track -= 1;
-		drive->sector = drive->sector % SECTORS_PER_TRACK[drive->track];
+		drive->sector = drive->sector * SECTORS_PER_TRACK[drive->track] / SECTORS_PER_TRACK[drive->track + 1];
 	}
 }
 
diff --git a/src/drive.h b/src/drive.h
index c41712a..e131c5c 100644
--- a/src/drive.h
+++ b/src/drive.h
@@ -4,7 +4,7 @@
 #include <stdbool.h>
 #include <stdint.h>
 
-#define DRIVE_LOOKAHEAD 16
+#define DRIVE_LOOKAHEAD 8
 
 extern const uint8_t SECTORS_PER_TRACK[40];
 extern const uint8_t BITRATE_PER_TRACK[40];