[coco] 6309 speed

[jdaggett at gate.net]

Gene

I seriously doubt that 20 to 30 MHz speeds could be obtained. At least not operating 
at 5VDC.  Maybe at 6.5 VDC. More realistic is 5 to 10 MHz. The problem wil lbe not 
all will do that. Maybe 1% of all 6309 will do 10MHz. Maybe 50% will do 5 MHz. 

Output waveforms alone are not a sufficient means of estimating the speed of a 
processor. The determining factor is the internal logic used to do the Instruction 
decode, addressing mode decode and ALU function. The problem is the delay time 
through the logic and the routing of busses through the chip. The 6809 uses a 
combination of synchronous and asynchronous logic. It is the asynchronous logic 
that is of most concern. 

Some designs try to do instruction decode and address mode docode in the same 
logic. While this may save area on the die,it can also slow things down as it may 
increase levels of gates in which two independent outputs must be obtained. A 
typical adress mode decode logic can be up to five levels of logic gates. In 
fabrication processes today one level of gate delay can be as little as 1 nS. Five 
levels now increases that to 5 nS delay and then you add anywhere from 1 to 2 nS 
for routing. Processes used to make ICs 25 yrs ago were slower. 

In designing the logic for a CPU, there is a trade off of speed and area. Sometimes 
to gain speed, processes need to be split up and thus take up more area. With the 
processes today pushing transistors that can switch at near one TeraHertz and 
junction widths that can be measured by the number of atoms across, are becoming 
realiazable. This allows for efficient use of area and parallel task to improve speed. 

james

On 3 Aug 2005 at 6:40, Gene Heskett wrote:

Date sent:      	Wed, 03 Aug 2005 06:40:43 -0400
From:           	Gene Heskett <gene.heskett at verizon.net>
Subject:        	Re: [coco] 6309 speed
To:             	CoCoList for Color Computer Enthusiasts 
<coco at maltedmedia.com>
Organization:   	None, usuallly detectable by casual observers
Send reply to:  	CoCoList for Color Computer Enthusiasts 
<coco at maltedmedia.com>
	<mailto:coco-
request at maltedmedia.com?subject=unsubscribe>
	<mailto:coco-
request at maltedmedia.com?subject=subscribe>

> Having looked at the waveforms coming out of it and finding that edge
> transitions are in the 10 nanosecond territory, my guess is that it
> could probably go quite a it faster, possibly as high as 20-30 mhz. 
> The only thing that would worry me is that there are some glitches on
> the address lines that would, if they occur a fixed time after a clock
> transition, begin to impinge on the memories 'setup' time when the
> clock speeds rise.