Re: Create Text & High Resolution into Screen

["Bill Garber" <willy46pa@comcast.net>]

"Eric Smith" <eric-no-spam-for-me@brouhaha.com> wrote in message
qh3cey10rj.fsf@ruckus.brouhaha.com">news:qh3cey10rj.fsf@ruckus.brouhaha.com...
> "Bill Garber" <willy46pa@comcast.net> writes:
> > I must differ with you here in that more than one character can
> > be fetched from RAM.
> You can differ all you like, but that's how the hardware works.
> I said that in one video cycle (which is half of a complete 1.023 MHz
clock
> cycle), one character is fetched from RAM.  It is unclear to me why you
> would think that the memory can provide more then one byte per memory
cycle,
> since the memory is only one byte wide.

Ok, you are right, but, I doubt anyone programming would fetch one
character at a time and commit it to screen memory since it must display
the entire line regardless of how many characters you fetch or how many
are fetched per cycle time. I would fetch an entire line worth before I
would
commit them to display memory. What everyone here is discussing is of
little importance to the actual functions in programming since it is all an
internal function of the CPU and other controller ICs. I can program
without knowing all of that.

> On the IIe and later machines, the memory is arranged to be wider (main
> and alternate banks accessed in parallel), so two bytes can be fetched per
> memory cycle, used for 80-column text and for double hires graphics.

Again this is information that is primarily not needed in order to program
anything from any input memory to display memory.

> > Entire lines can be fetched and displayed.
> Not in a single cycle.
> > Also, I can not buy anything being an "input" to a ROM ( Read
> > Only Memory ).
> If you don't "input" an address to a ROM, you're not going to get
> very useful output from it.  Read a data sheet on a ROM chip sometime.

Again, this is all done internally and is not really necessary knowledge
in order to create a working program.

Bill @ GarberStreet Enterprizez };-)
Web Site - http://garberstreet.netfirms.com
Email - willy46pa@comcast.net



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