More PDP-11 problems

[Don North]

Doesn't the console ODT for the KDF11 (11/23) normally operate in 18b 
address mode?
So if you exam/dep address 173000 from the console, it is the 18b 
address 173000
(ie, not extended to 773000). If you want to exam/dep the boot PROM 
address 773000
you have to enter that address.

Of course when the PDP-11 executes code with mem mgt off, the 16b 
address 173000
will be extended to the 18b address 773000, mapping the upper 4KW of the 
PDP-11
16b address space to the last 4KW of physical unibus 18b address space.

Patrick Finnegan wrote:

>Charles declared on Saturday 31 December 2005 20:32:
>  
>
>>When I examine memory at 173000 it's all 1's (177777) but I can
>>deposit and read data correctly into locations there. Shouldn't
>>the bootstrap program be copying its code there? 
>>    
>>
>
>No.  Because of 16-bit addressing vs 18-bit addressing, what the ODT 
>shows at 173000 is really "memory"/IO address 773000.
>
>  
>
>>Again, if the 
>>HALT line is being set for some reason, then the copy operation
>>can't take place... is that where I should be looking or am I
>>following a false trail?
>>    
>>
>
>There's no copy, reading from address 173000 gets translated by the MMU 
>to 773000 automagically.
>
>Pat
>  
>