Bryan Parkoff wrote:
"Michael J. Mahon" <mjmahon@aol.com> wrote in message
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Bryan Parkoff wrote:
"mdj" <mdj.mdj@gmail.com> wrote in message
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I doubt anyone is much interested in changing the resolution - all the
software stops working.
Matt
Matt,
I am sure that all software will work fine unless HiRes and DHiRes
are to be modified. Nothing is worried to modify any routines. All
software should run fine at 1 MHz.
How do you propose to shift out 8 bits in 14 cycles of the 14MHz clock,
so that video reads still interleave perfectly with the 1MHz processor
clock? Do you propose a 16MHz dot clock for text mode, and how would
that be synchronized with the 14MHz master clock?
Michael,
Good question. It would shift out 8 bits in 16 cycles of the 14MHz
clock when LDPS' is extended extra 2 periods. 14MHz crystal osc is
needed to sustain 60 frames vertically per second. It is important to
stick 14MHz crystal osc chip so 16 periods can be performed each video
cycle. It is only a way to change the timing equations in the HAL16R8
chip. I used to duplicate equations from PAL16R8 chip (same as HAL16R8
chip) to GAL16V8 chip. GAL16V8 chip is useful for reprogrammed
equations.
First of all, timing simulation in my C++ source code would help to
study 16 periods while modifying RAS', AX, CAS', Q3, Phase0, Phase1,
VID7M, and LDPS' to extend extra two periods like long cycle. If timing
simulation is correct according to my prediction, then equations can be
reprogrammed into GAL16V8 chip. It needs to modify video scanner to
sustain 57 video cycles instead of 65 video cycles in the IOU chip.
I hope to answer your question.
What you describe would lengthen the active horizontal line by 8/7 and
will slow down the video memory accesses to 7/8 MHz rather than 1MHz.
Doing so will cause numerous "ripple" effects to Apple II timing.
As I've said before, the Apple II is a carefully meshed set of gears,
and you can't change the speed of just one without a complete review
of system timing.
BTW, I can understand persuing this out of curiosity, but this sounds
like a lot of trouble just to use a 1-pixel wider non-standard font.
;-)
-michael
New, faster SUDOKU v2.0 solver for Apple II's!
Home page: http://members.aol.com/MJMahon/
"The wastebasket is our most important design
tool--and it's seriously underused."