"destructive read of a ROM"?

[Tony Duell]

> 
> Over on comp.terminals someone wrote this about the VT100:
> 
> 	"The power-on operation does a "destructive" read of the
> 	ROM-based firmware.  After so many power-ups, the ROM becomes
> 	unreadable. This was a design issue at the time - the technology
> 	to fix it did not evolve until the VT200 series."

The polite reply, I believe, is B*llsh*t!

AFAIK, based on reading the VT100 schematics, there's nothing special 
about the power-on operation. It just reads the ROMs like any other ROM 
read. And the VT100 firmware is run from ROM all the time, it's not 
copied into RAM at power-up or anything like that. So presumably, if this 
were true, the ROM would die if the terminal is left on.

There ahd been semiconductor ROMs for about 10 years before the VT100, it 
was not new technology at the time. And AFAIK none of them had this problem.

Now, there is an EAROM in the VT100 to store the configuration settings. 
It has a limited number of write cycles (i.e. saving new configurations), 
but AFAIK no limit to reads (and it is read on power-up to restore the 
configuration, of course). Maybe that's where this story originates.

-tony