Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cwjcc!gatech!mcnc!rti!sunpix!matthew
From: matthew@sunpix.UUCP ( Sun Visualization Products)
Newsgroups: comp.sys.apple
Subject: Re: Slot Assignments
Summary: To many bytes checked
Keywords: Slots, Booting
Message-ID: <700@greens.UUCP>
Date: 21 Jul 89 19:48:49 GMT
Organization: Sun Microsystems, Research Triangle Park, NC
Lines: 40

In article <7012@microsoft.UUCP>, Brian Willoughby writes:
| 
| 
| Dave seems to have answered all the questions, but I still haven't
| figured out why my Laser Universal Disk Controller (and Apple 3.5 Drive)
| won't auto boot on my II+.  I guess the ID bytes are incorrect for the
| routine in the II+ boot ROM.  I've tried it in slot 6 as the only drive
| controller, and the Applesoft prompt just appears, like there is no
| disk peripheral.
| 
| Oh, the woes of outdated systems :-)
| 
| Brian Willoughby
| UUCP:           ...!{tikal, sun, uunet, elwood}!microsoft!brianw


Brian,

     The reason why your UDC won't boot from power-on, is that Apple reduced
the number of bytes to check for a disk controller card from 4 to 3.  The
reasoning behind this?  Apple Pascal identifies drives by the same 4 bytes
as the old monitors use to do. ($01, $03, $05, $07).  Since Apple Pascal did
not know about the new disk drive, and since Apple Comp. did not want Apple 
Pascal confusing any non-Disk ][ drive as a Disk ][ drive, they eliminated
byte $07 from the list of valid ID bytes. (Actually it can be used to test to
see if the drive is a Disk ][ or not).

     The fix for your older system?  If you have modified, or are going to
modify, your monitor rom, search for the autoboot search routine.  It starts
by loading a value of $07 into one of the registers, just replace the $07 with
a $05.  Thats all there is to it. (Matter of fact, thats all Apple did to the
boot routine when they came out with the enhanced Apple //e roms).



-- 
Matthew Lee Stier                            |
Sun Microsystems ---  RTP, NC  27709-3447    |     "Wisconsin   Escapee"
uucp:  sun!mstier or mcnc!rti!sunpix!matthew |
phone: (919) 469-8300 fax: (919) 460-8355    |