Johnny Billquist bqt at update.uu.se
Mon Dec 7 03:47:34 CST 2015

On 2015-12-07 10:24, Pete Turnbull wrote:
> On 06/12/2015 17:27, Jerome H. Fine wrote:
>> In addition, even before that, you must match the CSR and
>> VECTOR with the DL port you are using.  On a Qbus
>> system with a DLV11-J, usually the first DL port is:
>> SET  DD  CSR=176500
>> SET  DD  VECTOR=300
>> On a PDP-11/23, there is an extra port at:
>> SET  DD  CSR=177570
>> if I remember correctly.
> I don't think so :-)  177570 is the switch/display register, which only
> exists on some Unibus machines.  It definitely doesn't exist on an
> 11/23.  Maybe you're thinking of the console CSR at 177560 with vector 60?

The display register also exist on some Qbus machines, such as the 
11/83, which have a two digit 7 segment display.

> Unibus addresses are the same as QBus, at least for I/O devices (things
> like memory management are done differently).

Uh. I/O addresses as such are just addresses. Devices might be similar 
between Unibus and Qbus. Depends on the device. There are many Qbus 
devices that are similar/compatible with their Unibus counterparts, but 
not always. DMA devices are not, for the obvious reason. However, they 
can still be "mostly compatible".

The memory management is compatible, so no, memory management is not 
done differently.

All that said, yeah, the second serial port is most likely not at 
177570. But that can be checked in the manuals...


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

More information about the cctalk mailing list