[Coco] Nitros9 high speed mode

[Joel Ewy]

I think this thread is suffering from insufficient specificity.  :) 

Paul, are you referring to the "High Speed Poke" (i.e., running the CPU
at 1.78 MHz instead of .89 MHz,) or running a 6309 in "Native Mode"? 

If you mean the former, then even stock OS-9 Level II always ran the CPU
in high (clock) speed mode.  In BASIC you achieve this by &HFFD9,0.  In
(Nitr)OS-9, this is done automatically in the machine language code
somewhere by storing a '0' in address &HFFD9.  The NitrOS-9 code is
available, so the actual implementation details can easily be examined. 
But ordinarily you would not want to turn this off.

If you are talking about the 6309's "Native Mode," that is also built
into the NitrOS-9 code.  What's called "Native Mode" is an operating
mode where the processor executes many of the CPU's instructions (those
present in the 6809 as well as the new 6309 instructions) in fewer clock
cycles -- getting more work done in less time.  The CPU can be switched
into and out of native mode in software.  I don't know whether NitrOS-9
6309 runs in native mode full time or switches out of it occasionally. 
We have NitrOS-9 developers on this list who can tell us for sure, but I
suspect that it runs in native mode all the time.  6309 NitrOS-9
probably also makes use of some of the new 6309 instructions such as DIV
and TFM that can process or move data faster than an equivalent series
of 6809 instructions.

So if you're asking about "Native Mode", then the way to avoid using
6309 features (CPU instructions and also native mode) is simply to run
the 6809 version of NitrOS-9.

JCE

Darren A. wrote:
>
>
>
>> From: "Paul Fitch"
>>
>> <snip>
>>
>> In that case, is the high speed mode turned on "automatically"?  And how
>> would I be able to tell?
>>
>> Or if not turned on automatically, what command or system call is
>> used to
>> tell Nitros to use the high speed mode?  And what command or system
>> call is
>> used to confirm that it has been done?
>>
>>
>> -- 
>
> I dont know if Nitros9 has any built-in facility for this, but when I
> want to test whether my code is running in fast mode or standard mode
> I use the following subroutine:
>
> MODETST   PSHS    A,DP,X,Y,U       ; PRESERVE REGISTERS
>          TFR     W,Y              ; Y = W (6309) / Y = #$FFFF (6809)
>          CLRA                     ; SET CC.Z (ASSUME FAST-MODE)
>          BSR     L2               ; PUSH FAST-MODE RTI ADDRESS
>          BNE     L1               ; BRANCH IF NOT IN FAST-MODE
>          TFR     X,W              ; RESTORE ORIGINAL VALUE OF W (6309)
> L1        PULS    A,DP,X,Y,U,PC    ; RESTORE REGISTERS AND RETURN
> L2        BSR     L3               ; PUSH STANDARD-MODE RTI ADDRESS
>          INCA                     ; CLEAR CC.Z CAUSE WE AINT IN FAST-MODE
>          RTS                      ; POP STANDARD-MODE RTI ADDRESS
> L3        PSHS    CC,A,B,DP,X,Y,U  ; STACK REGISTERS FOR STANDARD-MODE
> RTI
>          ORCC    #$80             ; SET [E]NTIRE FLAG FOR RTI
>          RTI                      ; RETURN TO MODE-SPECIFIC LOCATION
>
> This subroutine can be executed on both 6809 and 6309 processors. It
> returns with the Z flag cleared when running in standard mode (or on a
> 6809). It returns with the Z flag set when running in fast mode (6309
> only). All registers (including E and F) are preserved.
>
> Darren
>
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