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Coldstart your XE [message #280158] Thu, 06 March 1986 12:35 Go to next message
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Article-I.D.: inuxm.327
Posted: Thu Mar  6 12:35:16 1986
Date-Received: Fri, 7-Mar-86 07:29:46 EST
Distribution: net
Organization: AT&T Consumer Products, Indianapolis
Lines: 157
Xref: watmath net.micro.atari:2954 net.micro.atari8:45

                        ADD A COLD START RESET TO YOUR XE

               After I got my new 130XE, I began to get a little
          frustrated by the ram chips in it.  In order to do a cold
          start, I had to leave the machine off for at least 20
          seconds.  This is a *real* long time.

          I was convinced there had to be a better way.

               First of all a little history about what causes the
          problem.  When Atari switched to the XL/XE line of computers,
          they changed the reset button to do a hard chip reset instead
          of an interrupt like on the old 800's.  This means that every
          time the reset button is pressed the 6502 does a reset and
          starts over.  The software must determine whether this is a
          cold start (power up) or a warm start (reset button).  It
          does this by checking for a signature in the ram.  On the XE
          there are three bytes $33D, $33E, $33F.  If these three bytes
          are intact ($5C $93 $25) then it does a warm start.  If any
          of them are wrong then it does a cold start.

               The same day that I picked up my 130XE, I ordered the
          OMNIVIEW XE operating system from CDY.  This OS gives you
          several advantages.
               1. It does away with the need for a translator disk.  It
          looks like  the old Rev B operating system.
               2. It gives me an 80 column mode for some applications.
               3. It reverses the effect of the option key at
               4. It gives me ramdisk capability with any DOS.

          This OS only uses the first byte of the signature ($33D).

          I decided to fix my OMNIVIEW XE OS first.

          You will need access to an EPROM burner and a 27128 EPROM to
          make this fix.
         The fix.....

               My fix involves 'stealing' the reset vector and checking
          the keyboard secondary buffer.  This is a byte at $2F2 where
          the keyboard handler keeps the last button press to see if it
          should start auto-repeating on the next key stroke.  I
          decided to use 'shift esc reset' as my cold start method.  If
          the byte at $2F2 is $5C then the last key press was the
          'shift esc' and I trash the byte at $33D and let the system
          continue with a normal reset.  This will cause a COLD START
          without touching the power switch.

          The program.....

               LDA $2F2   load the last key buffer
               CMP #$5C   check it for 'shift esc'
               BNE EXIT   branch if it isn't
               LDA #$00   load a zero
               STA $033D  trash the signature
          EXIT JMP RESET  continue with the system reset vectors

          I made this change on the OMNIVIEW XE rom from CDY first.
          These are the changes for the OMNIVIEW XE rom.

             **********  DAVID YOUNG are you listening.  ***********

          The changes....

                 ADDRS  OLD  NEW
                  3FFC   29   20   power up reset vector
                  3FFD   EF   E9   power up reset vector
                  2920   44   AD
                  2921   61   F2
                  2922   76   02
                  2923   69   C9
                  2924   64   5C
                  2925   20   D0
                  2926   59   05
                  2927   6F   A9
                  2928   75   00
                  2929   6E   8D
                  292A   67   3D
                  292B   20   03
                  292C   CF   4C
                  292D   CD   29
                  292E   CE   EF

               These bytes were used for Dave's title 'David Young
          OMNIVIEW XE (C)1985'.  Sorry Dave, but this was the only safe
          place I could find!!!!

          If you boot without basic his message will be messed up.

          NOW THE XE......

               There are about 30 bytes of $00 in the rom at address
          $24A0.  This area was reserved for jump vectors, but was
          never needed.  The XE OS does a rom checksum during power up.
          So I changed that routine so it will always pass the check.

               This fix should also work on the XL series, but you may
          have to find a new location for the code.

          The changes....

                 ADDRS    OLD     NEW
                  3FFC     AA      A8   power up reset vector
                  3FFD     C2      E4   power up reset vector
                  3F90     38      18   defeat the rom check
                  24A8     00      AD
                  24A9     00      F2
                  24AA     00      02
                  24AB     00      C9
                  24AC     00      5C
                  24AD     00      D0
                  24AE     00      05
                  24AF     00      A9
                  24B0     00      00
                  24B1     00      8D
                  24B2     00      3D
                  24B3     00      03
                  24B4     00      4C
                  24B5     00      AA
                  24B6     00      C2

               If you have both systems installed with a switch to
          select one of them at a time, you may want to make an
          additional change.  Right now both systems use $5C for the
          first signature byte.  You might change one of them to use a
          different signature byte.  This would require finding all the
          places in the OS that it checks this byte and making the
          neccessary changes.

               Once in a while, if your system is 'locked-up' it may
          take two attempts to get a cold start.  It seems the first
          attempt gets the interrupt system working, then the second
          attempt does the coldstart.


          Hope this works for you.

          Ted Burger

          All the standard disclaimers apply.  I don't work for any of
          the above companies, some people claim I don't work at all!!
Re: Coldstart your XE [message #283120 is a reply to message #280158] Mon, 10 March 1986 07:53 Go to previous messageGo to next message
Originally posted by: DYOUNG@USC-ISID.ARPA (C. David Young)
Article-I.D.: ucbvax.8603101314.AA23043
Posted: Mon Mar 10 07:53:29 1986
Date-Received: Wed, 12-Mar-86 05:28:39 EST
References: <327@inuxm.UUCP>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 13

Regarding the coldstart from the keyboard, this has been a feature of
OMNIVIEW XL/XE for several months now. I chose to use the HELP key but
technique is about the same. By the way, I check 2 locations on RESET
to distinguish between coldstart and warmstart (not just 1 as your
note says).

The 130XE seems to have a real problem on powerup. I have talked to
many XE owners and many of them report problems with cycling power.
Does anyone know why the 130XE has this problem but not the 800XL?
Their operating systems are identical.

David Young
Re: Coldstart your XE [message #283121 is a reply to message #280158] Mon, 10 March 1986 07:58 Go to previous message
Originally posted by: DYOUNG@USC-ISID.ARPA (C. David Young)
Article-I.D.: ucbvax.8603101324.AA23200
Posted: Mon Mar 10 07:58:23 1986
Date-Received: Wed, 12-Mar-86 05:39:21 EST
References: <327@inuxm.UUCP>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 6

As a followup to my last message, anyone who wishes to upgrade their
OMNIVIEW chips can do so by sending in the chip with $10.00:
CDY Consulting, 421 Hanbee, Richardson TX, 75080.

David Young
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