UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Just got myself a commodore pet setup but not working

SiriusHardware · 10th Jun 2022, 4:56 pm

I note from a parallel 4032 thread over on VCFED - a machine with the other type of board as it happens - that it is possible for the startup chime to be present even when there are possible problems in zero page RAM, so the firmware which generates the chime must be careful not to use any RAM resources itself. If so that was a good decision by Commodore since it provides an indication that the CPU is able to execute firmware from the PROMs even when zero page RAM is not working. It's a useful diagnostic indicator.

10th Jun 2022, 4:56 pm	#31
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,575	Re: Just got myself a commodore pet setup but not working I note from a parallel 4032 thread over on VCFED - a machine with the other type of board as it happens - that it is possible for the startup chime to be present even when there are possible problems in zero page RAM, so the firmware which generates the chime must be careful not to use any RAM resources itself. If so that was a good decision by Commodore since it provides an indication that the CPU is able to execute firmware from the PROMs even when zero page RAM is not working. It's a useful diagnostic indicator.