[Coco] Re: [Color Computer] Re: CoCo video?

[jdaggett at gate.net]

On 3 Mar 2006 at 14:36, KnudsenMJ at aol.com wrote:

>  
> In a message dated 3/3/06 2:08:53 PM Eastern Standard Time,  jdag
> gett at gate.net writes:
> 
> >How  Fast for the 6809?
> 
> 
> 
> Well, let's see.  Some tinkerers managed to run a real 6309 up to 4  MHz.
>

I have see 68B09s ran at 3 MHz also.


> 7 years ago at Bell Labs we were designing ASICs that ran at 50 MHz, and  
> sections of some of them ran at 400.  ISTR the Xilinx FPGAs were running  around 
> 10 or 20 MHz.
>  
> By now, you could probably build a 6809 ASIC that would almost output the  
> results before you fed in the data ;-)  But RAM could be an issue -- though  
> fast static 64K or even 512K RAM might be feasible, too.  Maybe even put  64K 
> right on the chip -- in fact, I think we had ASICs with more than that back  then 
> in my project.
>

I doubt there are any of the current Coco users that would be capable of doing a 
6809/6309 in an ASIC. The cost is to prohibited. Yes it is likely that if one moved to 
130 nm process and took the core down to 1.25 VDC, an ASIC could even excedd 
100MHz or more. 

In reality and in small limited prodution, an FPGA would be a better alternative cost 
wise. The 6809 in an FPGA is a reality and speeds up to  20 MHz and is very 
doable. With some massaging of the HDL coded, even 35 to 40 MHz could be a 
potential. 

SRAM can be had downd to 15nS access time. That leaves you with a clock speed 
of 66 MHz. SDRAM can push down to 3.5nS or 133 MHz.  

  
> Any of this should be fast enough to enrich your fantasy life ;-)   --Mike K.

A 6809/6309 at 25 MHz would be sufficient. John Kent's 6809 core synthesized with 
a Webpack 8.1 states the 6809 core should run up to 28 MHz. I would suspect that 
in reality when you add more onto the FPGA the routing issues and gate loads will 
significantly slow this down some. Even 20 Mhz would be nice. 

A 20 MHz 6809 MPU with 8MB of external SDRAM, 2 ide ports, a parallel port, 2 
serial ports, 2 usb ports and a 512 color VGA module is actually doable. This should 
fit into a Xilinx XC2S300E part.  Even add some flash and a SPI port to access CF 
cards would enrich a fantasy even more. 

james