Homebuilt TTL and transistor CPUs - wierd logic
frustum at pacbell.net
Tue Jan 24 20:00:47 CST 2006
Chuck Guzis wrote:
> On 1/25/2006 at 12:50 AM ard at p850ug1.demon.co.uk wrote:
>>> Balanced trinary means place values go up by three each, but instead
>> Personally, I prefer negabinary (base -2). It uses 2-state signals, but
>> the column values are powers of -2 : . . .16, -8, 4, -2, 1
> Didn't the 8087 use ternary (base 3) for some of its internal logic?
No, my memory was that it used 4-state cells to encode two bits per cell
in the microcode rom. Rather than transistor/no transistor to represent
0/1, it used no transitor = 00, weak transistor=01, normal
transistor=10, strong transistor=11, or something akin to that.
That sounds great, except that the bit cells were a substantial portion
of twice as big as a simple one bit/cell design. There was some area
savings, but not 50%.
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