[Coco] CoCo 2 64K upgrade blues

[Dave Philipsen]

Like I said, it will probably work just as well either way. But engineers usually use a resistor to tie an input high for multiple reasons. I don't know the internal circuitry of the DRAM chip or what its maximum ratings are but sometimes an over-voltage situation can be a concern. Tying low directly to ground (without a resistor) is in most cases acceptable. 

In this case tying the pin to ground is probably not any 'better' than tying it to Vcc but it is preferred.

Dave

> On Aug 6, 2017, at 9:49 AM, Barry Nelson <barry.nelson at amobiledevice.com> wrote:
> 
> Why would tying the pin to ground be any better than tying it high to VCC? I would say leave it tied to VCC as it is simpler and will work just as well. The only difference is which bytes in the chip end up getting used.
> 
>> Dave Philipsen dave at davebiz.com  <mailto:coco%40maltedmedia.com?Subject=Re%3A%20%5BCoco%5D%20CoCo%202%2064K%20upgrade%20blues&In-Reply-To=%3C26a6bdec-924b-6acc-c150-196cc8be47ea%40davebiz.com%3E>
>> Sat Aug 5 15:14:08 EDT 2017
>> So now that you have given more specific information about pin 1 it is 
>> easy to see that you should pull/bend pin 1 so that it resides outside 
>> of the socket.  And the best would be to tie pin 1 of each chip to pin 
>> 16 (which is ground) of that chip. It would technically be better than 
>> tying all of the pins together and then to ground although that would 
>> probably work too.  The idea of avoiding sporadic reads or writes is a 
>> valid one but still has nothing to do with whether the computer is 
>> 'used' or not.  Maybe I am misinterpreting your use of the word 'used'.
>> 
>> Leaving pin 1 in the socket (and therefore tied to Vcc) is probably ok 
>> too but the preferred method is as mentioned above.
>> 
>> Dave
> 
> 
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