SEV question

[narf poit chez BOOM]

I believe I posted a sufficient understanding of that...Fyron.

[Fyron]

11111111 just translates into 8 latches set high, not "255".

[Baron Munchausen]

Fyron said:

If you want to be technical... A byte is contiguous sequence of a fixed number of binary digits. The exact size depends on the system in question (generally the smallest addressable word size). Even in C, where a byte is 8 bits, what those bits mean is arbitrary. It might represent integer values from 0 to 255, or it might be values from -128 to 127. Or it might just be a set of 8 boolean values.

And some of the old computers had very different byte sizes. Anywhere from 4 to 11 bits. For that matter, various current IBM hardware might also have different byte sizes. It's the Intel choice of 8 bits that we are living with in the PC world now.

[dmm]

I was going to make a snooty comment about 8 bits per byte naturally going with octal, but quickly realized that made no sense whatsoever. However, 8 bits goes well with hexadecimal. (Hex has digits 0 through 9 and then A through F, for a total of 16. That's probably as many digits as humans can comfortably handle.) So 8 bits per byte is 2 hex digits. A standard old-style keyboard had 26 lowercase, 26 uppercase, 10 numbers, 10 special characters, a space, a tab, and a return. That's 75 different characters, so ASCII code needed at least 2 hex digits. I'm guessing that was the driving force to have 8 bits per byte for PCs.

They could have used 3, 6, or 9 bits per byte, and then only used octal. But 3 is clearly too small to be useful, and 6 can't cover ASCII. (2^6 is only 64.) 9 bit bytes are overkill for ASCII.

[Baron Munchausen]

OK, maybe I am remembering WORD size rather than byte size...

http://en.wikipedia.org/wiki/Word_(computer_science)

In computing, "word" is a term for the natural unit of data used by a particular computer design. A word is simply a fixed-sized group of bits that are handled together by the machine. The number of bits in a word (the word size or word length) is an important characteristic of a computer architecture.

The size of a word is reflected in many aspects of a computer's structure and operation. The majority of the registers in the computer are usually word-sized. The typical numeric value manipulated by the computer is probably word sized. The amount of data transferred between the processing part of the computer and the memory system is most often a word. An address used to designate a location in memory often fits in a word.

Modern computers usually have a word size of 16, 32, or 64 bits. Many other sizes have been used in the past, including 8, 9, 12, 18, 24, 36, 39, 40, 48, and 60 bits; the slab is an example of an early word size. Some of the earliest computers were decimal rather than binary, typically having a word size of 10 or 12 decimal digits, and some early computers had no fixed word length at all.

[narf poit chez BOOM]

Plus, transistors.

2->4->8

Or, that's my guess, although I know very little about hardware architecture.

[MrToxin]

narf poit chez BOOM said:
Plus, transistors.

2->4->8

Or, that's my guess, although I know very little about hardware architecture.

Ultimately, it grew out of using electrical current to fuel memory. Magnetism could be used as well, but we'll stick with the electricity. A "bit" represents the smallest form of memory available, which is 0 (zero current) and 1 (non-zero current). If there was any measurable current, the value was ON or 1 or TRUE, depending on what you wanted to call it.

Things just got more complex from there. Because bits have 2 possible values, things just double in size as they progress. This is why if you look at the amount of actual bytes in a memory stick is never exactly what they advertise. If you measure things in binary terms, a kilobit is actually 1024 bits (2^10).

With a little math, one will find that a 512 megabit stick of RAM contains 536,870,912 bits of storage (actually, I stole the number from Wikipedia so there. ) That IS a power of 2.

At this point, I'm going to quit because delving into how memory works and all that funny computer architecture crap is weird and sort of makes your brain snap in half. I hate thinking about it so I'm not going to type about it. That gets into memory addresses and, as a silly little human organic brain owner, I have trouble thinking about ways to organize half a billion bits. Computers do it nicely, though.

[Fyron]

Baron Munchausen said:
OK, maybe I am remembering WORD size rather than byte size...

Well, a word is simply one or more whole bytes (a byte is the smallest possible word).

[narf poit chez BOOM]

Thanks, Toxin, but I knew most of that.

I'm not as empty-headed as I act.

[MrToxin]

Ah, word. Than, chances are, you know more about computer architecture then you think, that's what it's all based on. :V