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[aprssig] A funny packet story/joke (The KISS guys will get it)

Gregg Wonderly gregg at wonderly.org
Wed Nov 9 15:41:54 UTC 2005


Just to add the final math business...

Bill Herrmann wrote:
> Units:
> bit - binary digit - the good old 1 or 0.

binary means base 2 math is involved, a single digit can have the values from 0 
to (base-1) for any math in any base.  Thus, base 10 math uses values from 0 to 
9 for each digit, and base 2 math uses 0 to 1.  Base 16 (hexidecimal) uses 0 to 
15.  In base 16 math, to have single character values, for the digit values 10 
through 15, these values are represented by A, B, C, D, E and F respectfully.

in base 2, the maximum value representable in N bits is (2^N)-1.  So 32 bit 
memory addresses can represent ~4.2 billion distinct locations.  Switching to 64 
bit memory addresses will thus provide 4.2 billion times 4.2 billion distinct 
locations.  This is means that mostlikely the next common term for memory size 
(after terabyte, 2^40, goes away) will be petabyte (2^50).

> nibble - 4 bits

16 values can be represented, 0 to (2^4)-1. 0 to F in base 16

> byte - 8 bits

256 values can be represented, 0 to (2^8)-1. 0 to FF in base 16

interesting (to me) base 16 values that I remember from various intense use of 
hex for debugging 5ESS switches in the field.

20 = 32
40 = 64
50 = 80
64 = 100
80 = 128
a0 = 160
c0 = 192
f0 = 240

Interesting base 2 factors

2^10 = 1KB
2^16 = 32KB
2^20 = 1MB
2^24 = 16MB
2^30 = 1GB
2^40 = 1TB
2^50 = 1PB

Each 10 bits creates a new size measurment because that is a multiply by 1024. 
1024 for base 2 math is in line with 1000 for base 10 math.

Gregg Wonderly
W5GGW




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