In message <0e2fft85fpsopjjivminsu35ob8ut2a0j9@xxxxxxx>, Erik Mooney writes:
>On Tue, 08 May 2001 00:32:18 -0400, you wrote:
>
>>The board uses a 7404 Hex Inverter (14-pin DIP) to invert the address/chip
>>select line. I designed the board specifically for use with 4K ROMs. 2K
>>should also work, but anything larger than 4K (2732s) will not work.
>
>I'm no electronics whiz, but I recall someone mentioning that the inverter
>for the chip-select line could be done with a single transistor, no need
>for a (comparatively) bulky and expensive 14-pin DIP chip. Based on my
>sketchy knowledge, I think that's correct. Anyone? Wilkson?
Yah, you can do this...with a couple of resistors added. Cheaper, but only
by a few cents. A 7404 chip only costs 30 cents or so. A transistor is
maybe 10 cents and a resistor is 1 cent. These are rough figures of course.
But the relative costs are about right. In this case, since the pcb is
designed to fit a standard atari case, there's plenty of extra room for
the dip. Besides: 100 14 pin dips are easier to install than 100
transistors and 200 resistors! :)
Of course if you're making 100 boards, that 22 cents comes to 22 dollars! ;)
Ahh....tradeoffs, tradeoffs....
-Wilkson
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