[Coco] ceramics ...

Sun Sep 5 14:38:43 EDT 2004

Hi,

	I have no desire to overclock anything that I can't repair (kinda like 
investing). I will not overclock my tre (little chance of procurring a 
replacement for the GIME thing, nothing in sockets). I will not 
overclock my 12+ year old 386. I have no qualms about running my deuce 
at high speed. The only IC that would be difficult to replace is the 
SAM. I don't think the high speed has much of an effect on it. Plus 
sockets abound! And my Intel D815 (PIII at 800) and D845 (PIV at 2.4) if I 
knew how I might try. Just because I am curious as to what I can get 
away with. And if I toast something I can replace it.

	Mark, you asked why not just use the properly speced part. The answer 
is availability. 8 MHz 68k are not to difficult to find. 16 MHz are ... 
somewhat more difficult to locate. And quite a bit more expensive.

					kevin

jdaggett at gate.net wrote:
> Mark/Kevin
> 
> The 6809 is HMOS procoss,  High Speed NMOS. That is to say that all the 
> transistors on the IC are N type MOS devices. Unlike CMOS, Complementary MOS,  
> which will have N and P type MOS transistors. The advantage at that time, 1980, 
> was that NMOS was faster than CMOS but produced more heat due to larger 
> switching currents. The ceramic package has a lower thermal resistance to heat 
> than injection molded. Therefore the heat generated from the switching is removed 
> from the die faster than in injection molded plastic devices. 
> 
> Motorola marks the mask set on each of the parts. This will be a three or four 
> character string (D12A) on the same line as the date code. I have four different 
> 68x09E's that have four different date codes and four different mask sets. Back in 
> 1977 when the 6809  design was first started Motorola used 4 inch wafers to 
> fabricate their ICs. In fact in 1999 they still had one wafer fab facility that used 4 
> inch wafers fo rengineering runs. In the 80's the mos fab lines were all switched 
> over to 6 in wafers and later in the 90's to 8 inch wafer. Every time Motorola 
> changes the die, a new mask set is issued. This can be from a change in the wafer 
> size, a shrink of the die, or even to change one of about 25 mask layers used in 
> creatign an IC to correct a field issue. My guess is that one or more of the above 
> were done. Originally the wafer process was done on 1 to 3 micron process. 
> 
> My guess is that during the 80's the die went under a shrink. Most likely a 75% or 
> 63% shrink and ended up with 0.75 micron process. Each time there is a die shrink 
> the transistors get smaller. Smaller transistors use less current. By using less 
> current the overall dissapation of heat the device is speced for, 1 W, can now be 
> made using injection molded plastic. A cost savings of 3 to 5 cents per pin. At 40 
> pins that is significant savings. Smaller die and larger wafers yield lower costs and 
> more profit. Motorola started  in the mid 80's phasing out the ceramic package due 
> to costs and improvements in wafer processing allowed injection molded plastic to 
> meet the desired heat dissapation factors for many of their products that were in 
> ceramic. 
> 
> As I stated before the main enemy to ICs is heat. Current drain generates heat. 
> Increased clock speeds increases average current draw. Remove heat and up to a 
> certain point, the specified maximum clock speed can safely be exceeded. There is 
> a point to where even if the IC is cooled sufficiently that the design of the IC will not 
> allow any faster clock speeds. On the 6809 that is most likely between 4 and 6 MHz 
> buss speed. My best estimates are considering that the address mode decode logic 
> uses at most four gates. Each gate has between 3 and 5 nS propogation delay. That 
> would be pushing the internals of the processors at 6 MHZ. In honest, Even sith 
> sufficeint heat sink the Motorola 6809 will most likley start to crap out between 4 
> and 5 MHz. 3 to 3.5 is reliable with later mask set devices. IF the date code were 
> say 1985 or earlier, 3 MHz maybe pushing them. Post 1990 date codes maybe 
> capable of 4 MHz if kept cooled. 
> 
> One other note. The circuit and technigue that John K uses to bump up the clock 
> speed during internal processing and then slow down for I/O is an excellent scheme. 
> He pushes the interanls to 4 MHz and it might even work faster. The 6809e  parts 
> are a bit more difficult to do that with but the 6809 parts have the pins to coordiante 
> with slower peripheral devices. In doing that, the processor slows down to talk to the 
> outside world. During that period the part does have a few milliseconds to cool off. 
> 
> There are formulas to calcuate the interal temperature based on the package heat 
> resistivity and the external temperature. Also there is the factor of exchanging the 
> heat from the heat sink to the ambient air.  The heat sink needs to be sufficiently 
> large enough to remove the internal heat and dissipate it into the air surronding the 
> IC.  The hotter the outside air is the larger the heat sink needs to be. 
> 
> You just can not slap a heat sink on and crank up the clock. You have to do a bit of 
> math to calcualte the heat sink size. The major fault of over clocking is if the heat 
> sink method failes the IC will die a death real fast. 
> 
> james
> 
> 
> 
> On 4 Sep 2004 at 16:45, Mark Marlette wrote:
> 
> Date sent:      	Sat, 04 Sep 2004 16:45:28 -0500
> To:             	CoCoList for Color Computer Enthusiasts 
> <coco at maltedmedia.com>
> From:           	Mark Marlette <mmarlett at isd.net>
> Subject:        	Re: [Coco] ceramics ...
> Send reply to:  	CoCoList for Color Computer Enthusiasts 
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>>At 9/4/2004 12:01 PM -0700, you wrote:
>>
>>Kevin,
>>
>>Good question for james. I'm not sure why they had so many different
>>grades with such little base clock speed difference if you could just
>>add a heat sink to it and over clock it. ?????  This is exactly what I
>>was referring to.
>>
>>Mark
>>
>>
>>
>>
>>>Hi,
>>>
>>>        What kind of heat sinking? Were they ceramics?
>>>
>>>        Lets back up a bit. From what I know they sold 3 speed
>>>        grades of 
>>>the 6809:  6809 (1 MHz), 68A09 (1.5 MHz), and 68B09 (2.0 MHz). Are
>>>these made different?
>>>
>>>                                  kevin
>>>
>>>jdaggett at gate.net wrote:
>>>
>>>>Mark
>>>>We used 68B09's at clock speeds of 12 MHz, 3 MHz buss speed 24/7 for
>>>>months on end. Had little fail ure from that. Yes it is quite
>>>>possible to operate an 8 MHz 68K at 14 MHz. Again it may be
>>>>necessary to heat sink the chip though. james
>>>
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>>
>>
>>
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