bitfixer
Veteran Member
Hi all,
I finally got around to attempting to fix a 2001-8 that I got years ago. This one has had a bit of a rough ride, the case is very rusted and the board itself had all of its ROMs pillaged. The CRT is also disconnected, it's in storage somewhere and need to dig that out.
Using a ROMulator with a BASIC 1 rom set, I attempted a startup. The character ROM as well is missing, which is not replaced by the ROMulator, so i halted the CPU and dumped the shadowed Video ram to see what the CPU had written there. The full video ram space was filled with 0x20 (space) characters. Normally this would contain the "Commodore basic" message and ready prompt.
I confirmed that the PETTEST rom and my own ram/rom test do show the appropriate contents in video ram during execution.
It looks to me that a portion of the startup sequence completes, including clearing the screen. But another condition is not met which prevents it from getting to the basic prompt. Any guesses as to why the startup could be stuck after clearing the screen? Thanks
I finally got around to attempting to fix a 2001-8 that I got years ago. This one has had a bit of a rough ride, the case is very rusted and the board itself had all of its ROMs pillaged. The CRT is also disconnected, it's in storage somewhere and need to dig that out.
Using a ROMulator with a BASIC 1 rom set, I attempted a startup. The character ROM as well is missing, which is not replaced by the ROMulator, so i halted the CPU and dumped the shadowed Video ram to see what the CPU had written there. The full video ram space was filled with 0x20 (space) characters. Normally this would contain the "Commodore basic" message and ready prompt.
I confirmed that the PETTEST rom and my own ram/rom test do show the appropriate contents in video ram during execution.
It looks to me that a portion of the startup sequence completes, including clearing the screen. But another condition is not met which prevents it from getting to the basic prompt. Any guesses as to why the startup could be stuck after clearing the screen? Thanks