crank MaxIOsize from 32k to 64512 (126*512) to permit reading
exabytes tapes written with `tar b 126'.
it might make more sense to get rid of the MaxIOsize limit altogether.

Reference: /n/sources/patch/applied/scuzz-big-exabyte
Date: Wed Apr 13 02:05:52 CES 2005

--- /sys/src/cmd/scuzz/scsireq.h	Wed Apr 13 02:04:37 2005
+++ /sys/src/cmd/scuzz/scsireq.h	Wed Apr 13 02:04:35 2005
@@ -3,7 +3,7 @@
 	CtlrID		= 7,		/* default controller target ID */
 	MaxDirData	= 255,		/* max. direct data returned */
 //	MaxIOsize	= /*32*512*/ 96*1024,	/* max. I/O size */
-	MaxIOsize	= 32*1024,	/* max. I/O size */
+	MaxIOsize	= 126*512,	/* max. I/O size (e.g. exabyte @ tar 126) */
 	LBsize		= 512,		/* default logical-block size */
 };