At 9:47 AM +0100 12/31/01, Andrea Cocito wrote:
>  >In fact, I've been waiting for a chance to ask whether Apple's BootROM is
>>ROM at all!  A design which copies NVRAM into RAM, boots an operating
>>system, erases the RAM copy of NVRAM, and then potentially rewrites the
>>NVRAM seems like insanity to me, but apparently there are many PC BIOSes
>>that work the same way.  (I thought they were designed to have a
>>non-flashable area of ROM, so that you couldn't shoot yourself in the foot.)
>>
>>-- Derek
>
>The BootROM is not ROM. You can shoot yourself in the foot (been there,
>done that, sent the machine to Apple..).

Sun Ultra 1's are almost the same.  No real ROM at all.

They do have two duplicate copies of the PROM though and they flash 
them separately.  The hardware will boot if either half of the PROM 
is OK.

DS1 spacecraft is also like that, but we never had the nerve to 
reflash the A side.  ;-)
-- 
The opinions expressed in this message are mine,
not those of Caltech, JPL, NASA, or the US Government.
Henry.B.Hotz@jpl.nasa.gov, or hbhotz@oxy.edu