DEC Rainbow Hard drive.

Jeffrey Armstrong jba at
Fri Aug 31 10:38:36 CDT 2007

> Is the only difference between the -A and -B the firmware ROM? If you 
> the later firmware and put it into a -A mainboard would the machine (a) 
> still work and (b) let you boot from a hard drive (asuming you'd also
>fitted the controller card)?

I would be surprised if that did work.  There are some hardware 
differences in the 100A and 100B.  The graphics hardware is slightly 
different, and the quantity of memory on the motherboard is different. 
I'm sure there are also more subtle differences which I didn't mention. 
Anyway, it proably wouldn't work, but then again, I've never tried.

There are also other differnces that have nothing to do with the firmware. 
The 100A used an AC fan, while the 100B used a quieter DC fan.  The 100A 
power supply was not quite beefy enough to run the big hard drives, 
although it would unreliably work.  The power connector on the 100A for 
the second drive was also excessively short so it wouldn't reach the 
standard DEC hard drives alone anyway.  Usually, 100As have the block 
letter logo on the front, while 100Bs have the script Rainbow logo.


jba at
SDF Public Access UNIX System -

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