Re: VIC 26 Lines Bug - Truth or Legend ?

From: Marko Mäkelä (
Date: 2001-08-17 07:58:05

Hello Andre,

> i was recently pointed to the 26 Lines Bug.
> It has been said, that using this VIC-Mode, the VIC gets pretty hot.

Sounds like an urban legend, similar to the one that unauthorized copies
of audio CDs can damage the laser in a CD player.

The VIC is based on NMOS technology.  Its electric power consumption (and
thermal power dissipation) are rather independent of the clock frequency.

> I tried the text26 Program from frodo, but had no success in heating
> them more up.

If the video chip was manufactured in CMOS technology, where both states
(high and low) are actively driven by semiconductors, then it could heat
up a little.  During a high->low or low->high transition of a signal, it
can happen that both semiconductors (P-channel and N-channel) are
momentarily conducting at the same time.  This is why the power
consumption of CMOS devices increases with the clock frequency.

Has anyone made any experiments with overclocking NMOS chips?  Do they
overheat?  Can permanent damage occur if the chips don't overheat?
(Please use a 6502 or some other easily obtainable chip in your tests;
don't destroy custom Commodore chips that are no longer manufactured.)


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