The 68000 as PDP-11 Clone

[Ron Natalie <ron>]

> 
> Of course there are *some* differences. And of course the 68000 is a 
> 32-bit machine (crammed onto a 16-bit bus) while the pdp is a 16-bit one.

And it has the bytes in the wrong order.

> As far as relative code, the pdp is missing something. How do you
> load the address of a variable relative to the PC? This way:
> 
> 		mov	pc,r0			; address of `here'
> 	here:	add	#foobar-here,r0		; make relative
> 
Bad example, now what are you going to do with this loaded
address?  PDP-11 instructions allow things like

		tst	foobar(pc)

which is exactly equivalent to
		
		tst	foobar