> 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 that. 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. -tony
