[Coco] ceramics ...

[jdaggett at gate.net]

Kevin/Mark

Digital IC's speed specification is the maximum speed for a device such as there 
will guarenteed 100% compliance to the spefications of the IC. This is by far not 
the fastest the IC can run. Speed is often determined at die probe and by which 
package the die is placed in. Several parameters have to be taken in. Of one of 
the primary parameters of concern is heat. While the package temperature 
maybe warm, but the actual die temperature can be as much a twice the outside 
package temperature. The main goal is to keep the die temperature below 150 
degrees C. Heat is the ultimate killer of semiconductors. Above 150 C the 
physics of the semiconductor breaks down and all kinds of nasty things happen. 
Eventually, in MOS devices, the channels that allow electron mobility fail. Now 
you have a piece of silican  that is no longer functioning. 

Kevin you are right in one aspect, the ceramic parts can operate at higher clock 
speeds than say the common injection molded palstic parts. Ceramic conducts 
heat better the plastic. 

The second parameter that affects digital IC speed is the basic geometry of the 
transistors used to make the gates and the fabrication process, NMOS, HMOS,  
CMOS bi-CMOS and so forth. Smaller geometry transistors  have higher gain 
bandwidth product and thus smaller propogation delays between the gate and 
drain. 

If you can heat sink the pakage sufficiently a digital IC can be clocked as fast as 
it can accept it. That  generally is when the pin to pin propogation delay is slower 
than the clocked data. Generally speeking,  the propogation delay through the IC 
should not be more than 25 to 50% of the clock cycle. 


The GIME chip will handle higher clock speeds. T he problem is that to get 
proper HSYNC and VSYNC and color info correct it must be clocked at the 
perscribed frequency of 28.6363 MHz. Faster or slower will change internal 
timings that allow for proper NTSC and CG A video modes.

james
On 3 Sep 2004 at 4:15, Mark Marlette wrote:

Date sent:      	Fri, 03 Sep 2004 04:15:12 -0500
To:             	CoCoList for Color Computer Enthusiasts 
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From:           	Mark Marlette <mmarlett at isd.net>
Subject:        	Re: [Coco] ceramics ...
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> At 9/2/2004 09:04 PM -0700, you wrote:
> 
> Kevin,
> 
> Most parts have a designed clock that they were certified at and
> assigned when they were tested at their manufactured date. What are
> those clock speeds of the said chips? Seems to me to be a data book
> look up process. If theory doesn't work for you then just hook them up
> and try them out at the speed you want them to run. A bit of work
> since they are just chips and require a bit of work to connect up and
> test. Let us know what you find out though. Have some plan(s) for a
> new CoCo project here?
> 
> Mark
> Cloud-9
> 
> 
> >Hi,
> >
> >         No hardware. Just a pair of chips. So the question refers to
> >         
> > them. Think they would run at 14.3181818?
> >
> >                                   kevin
> >
> >Mark Marlette wrote:
> >>At 9/2/2004 11:57 AM -0700, you wrote:
> >>Kevin,
> >>Overclocking is generally not a good thing to do but it depends what
> >>you are trying to do. For instance, overclocking the CoCo3 is not a
> >>good thing due to the GIME. Can you tell us a bit more about the
> >>hardware that these CPUs are connected to? Regards, Mark Cloud-9
> >>
> >>>Hi,
> >>>
> >>>         I have a 68010 and a 68008. They are both 8s. Any
> >>>thoughts as to how high they could be SAFELY overclocked?
> >>>The plain 6809e in my deuce seems to run fine at 1.7 for
> >>>extended periods. But it does have a heat sink.
> >>>
> >>>                                   kevin
> >>>
> >>>Stephen H. Fischer wrote:
> >>>
> >>>>Hi,
> >>>>I thought I had one, but it is a 6800. I found a 6820 and a 8008.
> >>>
> >>>
> >>>
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