boot2 patch, please test.

Some embedded boxes do not have the keyboard controller, and this
patch adds a timeout so they do not get stuck waiting for it to
become ready.

Please test that this patch does not have any effect on normal
PC architecture machines.

Index: i386/boot2/boot1.S
===================================================================
RCS file: /home/ncvs/src/sys/boot/i386/boot2/boot1.S,v
retrieving revision 1.27
diff -u -r1.27 boot1.S
--- i386/boot2/boot1.S	14 May 2004 20:29:29 -0000	1.27
+++ i386/boot2/boot1.S	29 May 2004 19:49:52 -0000
_at__at_ -203,7 +203,9 _at__at_
  * Enable A20 so we can access memory above 1 meg.
  */
 seta20: 	cli				# Disable interrupts
-seta20.1:	inb $0x64,%al			# Get status
+seta20.1:	dec %cx
+		jz seta20.3
+		inb $0x64,%al			# Get status
 		testb $0x2,%al			# Busy?
 		jnz seta20.1			# Yes
 		movb $0xd1,%al			# Command: Write
_at__at_ -213,6 +215,7 _at__at_
 		jnz seta20.2			# Yes
 		movb $0xdf,%al			# Enable
 		outb %al,$0x60			#  A20
+seta20.3:
 		sti				# Enable interrupts
 		retw				# To caller
 /*

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