6702 chip

I start a new thread to discuss how the 6702 chip behaves, not how the 
Waterloo software uses it.

If you read the 6702 from basic, you always get the same number.
To change the number you get, write an even number to the chip and the an 
odd number.

If you repeat this you get a series of numbers that sort of looks random.

The first thing I noticed is that you never get two numbers in a row the 
same.  I wrote a short routine to check this.  After more than 32,000 
cycles, I never got two numbers in a row the same.  For random numbers, 
this should happen about every 256 numbers.

NOTE: this apllies only to writing the same two numbers to the 6702. If 
you change the two numbers that are written, you get two numbers the same, 
about as often as you would expect from random numbers.

The next thing I checked was the frequency distribution (how many times 
each number was produced).  The first run of nearly a thousand cycles 
yielded only 24 numbers.  This was with writing 0 and 1 to the 6702.
Writing 2 an 3, and 0 and 3 also produced only 24 numbers. Some of the 
numbers were shifted by plus or minus 2.  Going back to writing 0 and 1 
did not change the numbers back to what they were at first.  As wrote 
larger numbers to the 6702 more numbers were produced an at larger shifts 
from the base numbers, but they appear to be clustered around the original 
24 numbers. The most different numbers I got was 61, when I wrote 254 and 
255 to the 6702.

It appears the 6702 starts out with 24 base numbers and then modifies them 
each time a different number pair is written to it.

The 24 numbers I got on my first frequency distribution are:

3, 7, 34, 35, 38, 39, 81, 85, 112, 113, 116, 117, 130, 134, 162, 163, 166, 
167, 208, 212, 240, 241, 244, 245


wlevak@sdf.lonestar.org
SDF Public Access UNIX System - http://sdf.lonestar.org

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