VAXstation/MicroVAX 2000 CPU/FPU overheating?

Tony Duell ard at p850ug1.demon.co.uk
Fri Feb 29 18:46:23 CST 2008


> 
> At 9:26 -0600 2/29/08, Dave wrote:
> >Yes, I'm wondering if it's something like that, however how likely is it
> >that both devices would experience the same fairly-uncommon failure mode
> >at the same time?
> 
> I'm chiming in very late and probably not very helpfully, but is 
> there any way a decoupling cap in the vicinity of the FPU/CPU could 
> either load them or generate heat itself by beginning to short to 
> ground? My only VAX (4000VLC) had a fault like that in the reset 

Interesting idea.... I've worked with chips that had connectiosn for 
decoupling capacitors for particualr secitons in the chip (the most 
ovious being the Transputer which needs a 1uF capacitor between 2 of its 
pins to decouple the clock multiplier PLL). In general, these components 
are not conencted to a power line or ground other than through the chip.

I have no idea if the VAX 2000 chips are like this, but if they are, then 
a leak in one of those cpacitors would certainly cause thigns to run hot.

-tony



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