Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!indri!dogie.macc.wisc.edu!uwvax!puff!cat28!blochowi
From: blochowi@cat28.CS.WISC.EDU (Jason Blochowiak)
Newsgroups: comp.sys.apple
Subject: Re: JMP/JML revisited...
Message-ID: <2762@puff.cs.wisc.edu>
Date: 11 May 89 00:15:41 GMT
References: <8905101021.aa15777@SMOKE.BRL.MIL>
Sender: news@puff.cs.wisc.edu
Reply-To: blochowi@cat28.CS.WISC.EDU (Jason Blochowiak)
Organization: U of Wisconsin CS Dept
Lines: 28

In article <8905101021.aa15777@SMOKE.BRL.MIL> JWANKERL@UTCVM.BITNET ("Josef W. Wankerl") writes:
>I didn't mean JML... I meant BRL.  (They both have L so I guess that's
>what messed me up.  I have it straight when I program...  :-)
>
>They're both 3 byte instructions, but is there any difference in
>execution time?  On range?
	According to Leo J. Scanlon's _Apple IIGS Assembly Language
Programming_, a BRL takes 3 cycles, and a JMP Absolute also takes 3 cycles.
I've learned not to trust the book, but this seems reasonable. Anyways, it
would seem that their range is exactly the same, it's just a matter of how
one gets to the destination - by using an absolute, or by using a relative
address. The BRL won't require an entry in the relocation dictionary, but
the JMP will - then again, I don't think this is a real consideration while
coding, unless you're REAL tight for memory. Obviously, BRL is relocatable,
so you can use it in a chunk of code that will move around after being
loaded (btw, there's a neat "relative JSR" that can be done with a PER and a
BRL - I think it's PER #2, but I'm not sure). So, I suppose BRL has the
advantage when you're within your own code, but isn't much good for calling
ROM locations (which would only be useful in ProDOS 8 programs, methinks) or
a fixed address in your code (which seems pretty daft, seeing as the
relocator exists).
>  -Gonzo


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		Jason Blochowiak (blochowi@garfield.cs.wisc.edu)
			"Not your average iconoclast..."
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