Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!shadooby!ginosko!uunet!munnari.oz.au!csc!ccadfa!usage!basser!metro!ipso!fawlty!johnmac
From: johnmac@fawlty.towers.oz (John MacLean)
Newsgroups: comp.sys.apple
Subject: Un-documented ROM vector
Message-ID: <504@fawlty.towers.oz>
Date: 5 Oct 89 04:41:55 GMT
Organization: Tower Technology, Lane Cove, NSW
Lines: 33

Did ye all know that in ROM version 01 (the second ROM version we got
in Aus) there is a routine that checks for the existence of the expanded
ROM containing all the extra tools?

I cannot remember the vector off hand - its around $E1/00?? and is one
of the first or only unused vectors in the original Firmware Reference
manual. 
On a warm boot this vector is JSLed to and a routine in bank $FE 
checks for the existence of a string "ROMTOOLS" in some other bank
(I think it is $F8). If it is there, then a JSL is made to that 
bank presumeably to start up the ROM tools, and a second JSL is
made to the bank to retrieve a version number?

If you want to find this code have a look for the string - I think
it is in the first few pages of bank $FE but it about a year since I
found this.

Shoot me down if this is documented, but I have not seen it ...

The interesting thing is that this means that the code for expanded
ROMs was at least being tested back in 87 (maybe early 88) when we
received the ROM 01 update.
It also means that an add on ROM card (attachable to an AE card via the
connection for eg) could be made to put all the tools into ROM. Such an
upgrade might be more cost effective than a motherboard replacement,
and would work with no software changes ...

John MacLean
-- 
Internet: johnmac@fawlty.towers.oz.au			  Phone: +61 2 427 2999
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Snail:    Tower Technology
	  31-33 Sirius Rd, Lane Cove, NSW 2066, Australia.