CBM 8032 won't boot

[Phlup[]

Checking an 8032 before putting it on the market, I get the startup beep but then see the attached screen. Any thoughts? Thanks.

 

[Hugo Holden]

After the boot up, for some reason, the CPU could not find any valid code to run and was sent to an address with 00 in it(the BRK opcode), when this is the case it jumps to the TIM (terminal interface monitor). This reports the contents of the CPU's registers, it is also a very useful monitor for inspecting memory, loading & running programs etc.

Possibly this represents corruption of some bytes in the ROM's holding BASIC.

Try typing X which should exit the TIM and go back to BASIC, if BASIC is working that is.

There was also some modification that caused the computer to go directly to the TIM after power up, so if BASIC works when you exit to it, maybe this PET has that mod.

TIM - C64-Wiki

www.c64-wiki.com

 

[daver2]

The /DIAG signal enters one of the PIAs or the VIA chip. I can't tell you which one at the moment). If this pin is LOW on powerup, this is the behavior you will get. If the PIA/VIA is duff, you may also get the same outcome.

Dave

 

[dave_m]

The /DIAG signal enters one of the PIAs or the VIA chip. I can't tell you which one at the moment). If this pin is LOW on powerup, this is the behavior you will get. If the PIA/VIA is duff, you may also get the same outcome.

Dave

Daver, no, as Hugo says, it is a BRK (B*) to the Monitor. If /diag was held Low, it would perform a Call to the Monitor. The Program Counter is sometimes in low RAM and sometimes at $Dxxx.I would guess bad ROM or bad zero page RAM.

 

[daver2]

True. I didn't check the PC.

The problem with being in a rush...

Dave