Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!oliveb!apple!farrier
From: farrier@Apple.COM (Cary Farrier)
Newsgroups: comp.sys.apple
Subject: Re: JMP/JML differences
Message-ID: <1729@internal.Apple.COM>
Date: 9 May 89 15:51:55 GMT
References: <8905081131.aa03291@SMOKE.BRL.MIL>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 28

In article <8905081131.aa03291@SMOKE.BRL.MIL> JWANKERL@UTCVM.BITNET ("Josef W. Wankerl") writes:
>
>I've just been wondering what the advantages vs. disadvantages of
>using a JML instead of a JMP would be.  I guess an advantage of the JML
>would be that it wouldn't need space in a loader relocation dictionary.
>Is there any other difference??

	Actually, any label reference (which isn't thrown out by optimizing),
	except brances (they contain an offset in the operand), will find 
	its way into a relocation table.

	The difference between a JMP and a JML is that a JMP instruction
	can only jump to an address within the current code bank, while a JML
	can jump to any address in any bank.  The reason is because the JMP
	only uses a 16 bit address, and the JML uses a 24 bit address.  The
	JMP will affect only the program counter (PC), and not the code bank
	register (K), while the JML will affect both.

	Most decent assemblers will convert any JMP instructions to JML if
	long addressing is required, so your code may vary.

Cary Farrier


-- 
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| Cary Farrier | farrier@apple.com | Ok, how's this for net traffic?
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