Re: [Pgubook-readers] Initial feedback

[Jonathan Bartlett]

Thanks for your feedback!  I'm starting to collect patches for the book.
I'll probably put out a new one in 6-9 months.

> * The data bus is introduced as a mean to fetch data from memory
> (page7, 2nd paragrapgh). Right before, however, it is said that the CPU
> fetches the content in the address stored in the program counter. In
> that context it is emphasized that memory cells are of equal type, and
> that what differs is the way the numbers are interpreted, which makes
> me wonder whether the data bus is used as well in that case, and if not
> how is the instruction actually fetched and why the difference.

Yes, I need to make it more clear the data-fetching process.  The CPU does
fetch the next instruction, but does so through the data bus.

> * In that introduction there is a conceptual separation between memory
> and CPU. But because of that the sentence "On x86 processors, a byte is
> a number between 0 and 255" surprised to me. It made me wonder why the
> processor, which until now was something kind of independent,
> determines the size of the cells and not, say, the memory manufacturer.

Good point.  Yes, the processor has to control the size of bytes, because
the processor is what has to load, manipulate, and store the contents of
those bytes.  In addition, historically there have been processors with
other byte lengths, but today it's pretty much between 0 and 255.

> * I appreciated the comment about the simplifications being made and
> the list of keywords to find further information.

My goal of the next edition is to include that in the appendix.  One thing
I _wanted_ to do with the book is also release a printed version of the
LSB documents.  However, after reading through them it became apparent
that they simply skipped over anything contained in the UNIX ABI manuals,
even though this is essentially proprietary information.  I hope to
(someday) make free versions of this info available.

Thanks for your input!

Sincerely,

Jonathan Bartlett