[Coco] Re: CoCo gcc project

[jdaggett at gate.net]

Interfacing to the MC68882 would be easier. Costwise both approaches are about 
the same. The FPGA maybe a slight bit cheaper depending on which one and how 
big it needs to be. A quick price comparison:

Digikey has the MC68882 for $52 and the Xilinx Spartan II with 150,000 gates is 
$28. The software to put in the FPGA is free and the software to program the FPGA 
is free. PCB costs for either approach is about the same. Other support ICs will add 
some more cost, maybe another $5. 

One advantage the FPGA has is that it is configurable to specific needs. It can be 
as small as we want or as large as we want. It can be configured to work directly 
with the 6809.

james


On 2 Nov 2003 at 13:06, Theodore A. Evans wrote:

> On 11/02/03, jdaggett at gate.net wrote:
> 
> > My thoughts on CORDIC approach is to do the algorithms in FPGA and
> > stick the chip off as a coprosessor. One can tap off the 28MHz clock
> > of the Gimme chip and buffer it to provide the clock to the FPGA.
> > Inside a Spartan II/IIe part you can then double that frequency and
> > run the coprocessor at 56MHz. If it takes the Cordic processor 21
> > cycles to generate the sine of an angle, that will be about 375 nS. 
> > 
> > There are a few cordic cores for FPGA that are open and free to use
> > on the internet. Just need to write and add more functions.
> 
> If you are going to go to all that trouble, it is probably easier,
> cheaper, and faster to use a dedicated math coprocessor like the
> m68881 or m68882 instead.
> 
> -- 
> Always yield to temptation, it may never return.
> Theodore (Alex) Evans            | alxevans at concentric.net
> 94-1071 Kepakepa St. Unit #C-1   | http://www.concentric.net/~alxevans
> Waipahu, HI 96797                | ICQ 78089262 x                     
>           | (808) 676-0123         2B v ~2B = ?
> 
> 
> -- 
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco