Multi-platform distribution format (Was: Backups [was

tony duell ard at
Mon Sep 21 11:40:38 CDT 2015

> If it was possible to perform a LLF using the same RX50 drive on
> the Rainbow, what was the reason why an LLF could not also be

It is. Remember the RX50 is just a drive, it does not include any of
the controller electronics.

> performed on a PDP-11?  There seems to be a number of possibilities:

> (a)  There was some hardware that the Rainbow had which was missing
>        on the PDP-11 systems

It's more the reverse!. The Rainbow just has a standard controller chip on the 
processor bus (I forget which processor, I can look at the schematics if you
want). The controller chip can do what is needed for a LLF, and there is
nothing in the way to prevent software from sending the commands to do

On the PDP11 there is a lot more stuff between the processor and the disk
controller chip. Even the Pro 300 series has a microcontroller (8051?) on
the floppy controller board. Therefore the processor you can program
(PDP11) can't do arbitrary things to the disk controller chip, it is very likely
that sending the right commands to do an LLF is one of the things you
can't do.


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