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1. paulrickards (paulrickards@mastodon.social)'s status on Monday, 23-Oct-2023 10:38:38 JST paulrickards

   Current status.

   #AppleLisaClone #RetroComputing

   • paulrickards (paulrickards@mastodon.social)'s status on Monday, 23-Oct-2023 10:38:36 JST paulrickards

     in reply to

     It seems the Lisa thinks it only has 128Kbytes of memory, according to these memory locations ($294-297 maximum physical address and $2A8-2AB total memory). Need to look into the boot rom to see how memory size is determined.

     #AppleLisaClone #RetroComputing

   • paulrickards (paulrickards@mastodon.social)'s status on Monday, 23-Oct-2023 10:38:37 JST paulrickards

     in reply to

     Deep diving into buss error handling by reviewing the previous posts and the Lisa Boot ROM assembly.

     http://bitsavers.org/pdf/apple/lisa/firmware/Lisa_Boot_ROM_Asm_Listing.TEXT

     If I understand this correctly, memory $282 should hold the address that caused the bus error. In my case, I get

     282 0002 0000

     which I think is $020000 (high byte is ignored). Does that mean the problem is occurring at position 128kbytes in the RAM card? Not sure how to map that to a component/components yet.

     #AppleLisaClone #RetroComputing

   • paulrickards (paulrickards@mastodon.social)'s status on Monday, 23-Oct-2023 10:38:37 JST paulrickards

     in reply to

     Using the service menu and the display memory command 01FF00 with a length of 100 shows the contents of memory just fine.

     As soon as I cross the boundary into 020000 (say, with display memory 01FF80 length 100), the machine abruptly reboots and beeps twice (lo/hi).

     Is this a RAM card problem or a MMU problem?

     #AppleLisaClone #RetroComputing

   • paulrickards (paulrickards@mastodon.social)'s status on Monday, 23-Oct-2023 10:38:38 JST paulrickards

     in reply to

     A couple of posts about troubleshooting bus errors in a Lisa.

     https://lisalist2.com/index.php/topic,263.0.html

     https://lisalist2.com/index.php/topic,266.0.html

     #AppleLisaClone #RetroComputing