[Coco] CoCo gcc project

[John Donaldson]

  The fastest divide is a shift command. IIRC, one way does multiply by 
2 the other does divide
by 2.

John Donaldson


KnudsenMJ at aol.com wrote:

>In a message dated 10/31/03 3:16:59 PM Eastern Standard Time, 
>jdaggett at gate.net writes:
>
>  
>
>>I wished the 6809 had a DIV instruction!!!! Some base code to implement 
>>    
>>
>what the 
>  
>
>> HC11 FDIV and IDIV instructions would be nice. Then you have 16 bit by 16 
>>bit divide. 
>>    
>>
>
>To merge with another thread, the Star Wars arcade game used a 6809 and had 
>an outboard hardware divide board, built of 7400-series TTL ICs.  Don't recall 
>how many clocks it took.
>
>If you look at the stock OS-9 C libraries, you will find various integer and 
>floating point math routines, including signed and unsigned divide routines.  
>Don't know how optimized they are.  From my own gory/glory days of writing 
>math routines, ISTR that non-restoring divides are faster, at the expense of a 
>few more lines of code, but you don't execute all the code for every bit.
>
>For a different approach to trig and other functions, check out BASIC09's 
>math routines, which use CORDIC rotation approximations -- faster than series 
>expansion.  You'd have to figure out how they work and re-write for C's floating 
>point.  Oh yes, 6809 C library already includes "double" precision routines, 
>no doubt really slow, but what can you expect?  And who would use them on a 
>6809 anyway?  --Mike K.
>
>  
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