/usr/src/sys/i386/boot/biosboot/boot.c
--- boot.c.orig	Sat Feb 28 07:56:14 1998
+++ boot.c	Fri Jul 17 17:19:17 1998
@@ -102,6 +102,9 @@
 	 * The default boot device is the first partition in the
 	 * compatibility slice on the boot drive.
 	 */
+#ifdef FORCE_BOOT_HD
+	drive = 0x80 + FORCE_BOOT_HD;
+#endif
 	dosdev = drive;
 	maj = 2;
 	unit = drive & 0x7f;