On 8/18/2015 7:46 AM, Paul Koning wrote:
> 
>> On Aug 17, 2015, at 10:48 PM, Jay Jaeger <[email protected]> wrote:
>>
>> BR level is the bus request level for an Interrupt.  BR 4 is typical.
> 
> On Unibus machines, more of the BR levels were used.  The rule of thumb was 
> BR4 for slow devices (like terminals and printers), BR5 for fast devices 
> (disks and tapes), BR6 for real time critical devices (clock, also DECtape 
> because you had to respond to a “read block number” interrupt fast enough to 
> start reading the block before it passed over the heads).  BR7 could in 
> theory be used by devices but I don’t believe it ever was in practice.
> 
>       paul
> 

Yes, but this discussion regards an RLV11.

JRJ

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