On 2018-04-10 09:12, Johnny Billquist wrote:
On 2018-04-10 03:28, Mark Pizzolato wrote:
I see 2 approaches to adding support for different unit numbers:
1) A unit number is settable uniquely for each of the 4 drives that can be attached to any of these controllers.  This would map to a conceptual Drive Unit
Plug.  Did these exist on DEC MSCP drives?

Yes they did.

I should actually add that for the RA60, RA80, RA81 and RA82, this plug is binary coded with 8 tabs that you can cut off, and allows you to select a unit number between 0 and 255. On the RA90 and RA92. The front panel of the disk has a display and buttons, and you can select the unit number from there, and it goes between 0 and 4095. The RA70 disk has dip 8 dip switches where you can select the unit number. The RA70, RA71, RA72 and RA73 can also be placed in a larger box called the SA7x (I think, can't remember if the x was supposed to be replaced with some number depending on configuration), where you then have a display that control up to four disks in the container. Each disk can then be managed by a front panel on the SA. And each disk has its own unit number selectable on the front panel, and the unit number goes from 0 to 255 (not 4095 as I said in a previous post). Or at least my memory right now is 0..255 for the RA7x drives, but I could be remembering wrong.


Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: b...@softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol
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