Completely unsubstantiated.DigitalQuirk wrote:I think it possible that the 6560 is more sensitive than other chips, possibly because it does run hotter, which may lead to it failing first. Telling people it fails because of heat may cause them to replace the chip or their Vic, put on a heat sync, but continue to use the same failing power supply which otherwise seems to work. This false sense of security may cause them to go through a few 6560's before they realize what's going on.
In the C64, DRAM always fails first because it uses more voltage sensitive HMOS/CMOS technology while Commodore made chips use less sensitive NMOS technology.
If the 6560 was more sensitive to inadequate voltages because of its high running temperature, how come the 6567 in the 64 which runs even hotter does not fail before the DRAM chips, which produce little heat, when power supplies fail?
Its a question of doping used in the silicium chips and finding exact details about this on the internet is almost impossible. The fact that I can't provide a link to that specific information on the internet doesn't mean this isn't very well known to people experienced in semiconductor production.
Anyways, if you suspect your Commodore brick is the culprit, why don't you simply take a multimeter and check its output voltage?
BTW, you confuse personnal experience with "hear-says". C128 PSUs can and have destroyed equipment they power in the past. Old PC PSUs too. However advances in technology have made this impossible in good quality modern PSUs, including wallwarts. I am not going to give a power electronics course in a forum to demonstrate that.
It seems to me that according to you the bounds of human knowledge is limited to the internet. The fact that I cannot easily find a link to confirm a specific claim does not mean its unsubstantiated. I know for sure you can easily find that if you pay a trip to any good engineering school's library.
Anyways, as I said, Commodore wasn't the only one back in the days to use NMOS/HMOS fabrication process. If you look on wikipedia, you'll see that early intel 8086 and Motorola's 68000 used it too. Since these substrates were made the same way, I don't see why Commodore's chips would be affected differently by temperature. The impact of high temperature on the life span of these chips is thoroughly documented in many vintage databooks by these manufacturers.
Added edit:
The 6567 of the Commodore 64 is the only chip that I know of that dissipates more heat than the VIC-20's 6560.
Here is what Benj Edwards of PC World magazine had to say about this chip recently:
From here.The VIC-II chip, which was originally ceramic, was changed to plastic in later runs of the C64. Unfortunately, the plastic chips didn't conduct heat as well as the ceramic chips, and the VIC-II became a common point of failure in many C64 machines.
AFAIK, the 6560 is the most common point of failure in the VIC and it happens to be the chip that runs the hottest.
Any intelligent person can draw their own conclusions.
Drama...misspellings...Déjà vu! Notice how it's always the same pair! 
