True Coder # 001
(C) Rob F. / Entire Group
Kowtow, dear readers. This
column is devoted to a certain spirit, which
originated in the world Speccy.
I think each is the word "Speccy", -
associated with something sweet and throbbing heart. Well, of
course, where else can you play the game MYTH? Not on a PC, and
yes do not for Ammy, no talent in graphics, no
magnificent Coding'a. So, on the coders ... This rank is not so
easy to get, as it seems. In general, the loaders at Busick
do not get off. However, the true Coder can write on Vasik
Scroll, albeit with mats in the shower, but write. For a long
time communication with other guys, I have deduced a simple
formula encoder - eternity. With each day, a true coder, will
come up something new and new. And most likely,
same problem it will solve one thousand
ways. Unlike others, he will
a thousand times to reinvent the wheel, it is
so Spectrum'isty know a thousand ways to highlight the
on-screen point, and it is therefore, they have found the best
way for its appearance. And like it seems that
faster is not possible, but still some one comes up even faster.
Sometimes I think that the Speccy come up with some packer
information squeezed into one BIT or three BIT'a;) is
ridiculous, of course, but you never know? Although, like, this
is not possible. Do not ... I was wondering, can only
decompressor would be great! =) Just kidding, of course ...
And sometimes there are guys on the Speccy,
who have tasted success, start it
sinking. Then they become ridiculous, starting to say stupid
things like that, that a Z80 is glitches, ie commands that
he does not perform. There are, of course, but quite
not what they describe. Here in this column I
and wanted to share with you the true value.
Corporate Speccy ...
In fact, Speccy unique in that
overseas, that is original, options
one hundred percent compatible with each other.
But we have difficulty to understand it, because we invaded a
kiddies Speccy - Scorpion'y, Pentagon'y, Profi, Leningrad'y and
other options. I can not say that have tried everything, but
twenty versions I went over and studied thoroughly. And as he
studied the original version with the "plus" and without them.
Therefore, to inform you that on the firm
Speccy in one interrupt 224 * 312 = 69888
cycles, if we multiply 69,888 by 50, then
obtain 3494400 cycles per second. It turns out that quartz is
not 3. 5 3. 494400MHz, and from We can conclude that each
interrupt somewhere lost 112 ticks. Where same? Yes, anywhere,
just the frame rate from 50 Hz, while 50.0801282051282051 Hz,
that's all wisdom. However, the software method, we
can count only 69,868 cycles, since the 4-D beat signal INT
exhibits interruption, and the 16-Tb cycles to execute
of the interruption. Interrupt can not
suspend execution of one command, so
Interrupt response will be after completion of the team.
Shovels kids Speccy ...
Looks like we just figured to separate
parts and turn them into sex hundreds of logic is
that bourgeois molded into a single chip. So
, the signal INT'a our options
Speccy turned into a bunch of resistors and
capacitors. Now beginning its length measured not in cycles and
in microseconds. Therefore, only our Speccy, need for
confidence to model lot NOP'ov before exiting the interrupt.
There are some instances, in which the interruption begins in
the middle of the monitor, I have personally seen is in
Leningrad'ah. Of course, I understand that have the following
version of the monster, and there is removed. But I think that
if electronics less cursed with encoders,
and encoders with electronics, who then together they
would have made a very good option
Speccy. So far, I have found only one Speccy, which is almost
100% repeats firm Speccy, is Lions.
Inhibitory region of memory ...
As it is not unfortunate, but firm Speccy slow, but not
always. In this fact there are pros and, of course, downsides.
Very good plus, I've always
enjoyed until everything is obsessed with
Pentagon'ah, a team of HALT, which
performed in the decelerating region interrupts. Last cycle,
performed in this team, always coincide with the last bar of
the end of the sweep screen and the first tact in the new
interrupt will be exactly on the line monitor in the first
pixel. So it is possible do horizontal multicolor that
used bourgeois in their programs.
For example: Mask 3, or Dark Star or ... In general, there are
still masterpieces in that regard, I'm sorry, I do not
remember, long ago it was. By the way, its first multicolor I
made back in 1992nd year on GENS'e somewhere still
lying on tape. It was Multicolor Scroll to the curb, as I
remember, decided podlomat Khampton'a, and told him
that will draw something on the curb, so was born
Border-Scroll.
Slowing down further ...
If someone is faced with a brand Speccy, or his dear
children, in which the same slow memory, you noticed that no
God forbid to leave the interrupt vector (I) in
range from 64 to 127 or (192 to 255,
provided that includes inhibitory page), and for all this to
try something written to disk, then you are guaranteed
errors on the disc. Generally, the zero track zaportite, or
rather burn any rubbish there. Here is a simple parsley, even
if prohibited by interrupting the signal WAIT, is still
installed, because the processor tries to read the value from
the address of the interrupt vector, as he points to the
braking area of memory. In general, all waiting for each
other. Well, while OUTI begins to occupy than 16 cycles and
then 20, then 24, it all depends on what part of
OUTI gets signal INT'a. And if you try to execute the program
in the decelerating memory area, so even with a vector in the
braking area, then your team will be triple in tact. The most
fun occurs when the processor himself puts WAIT, and can not
assume command code. For example, start to transfer the entire
memory LDIR'om on itself, and do it multiple times.
M1 LD HL, 0
LD DE, 0
LD BC, 256
LDIR
JMP M1
Well, hang on interrupts the music and
executable LDIR toward retarding memory. Since the processor in
one of those moments will expose himself waiting and finally or
not fulfilled INT, or LDIR. By the way, slows it all only when
something appears on the screen, or rather, our screen area.
Therefore, if you will play its prog before starting to display
Screen capable then no one will slow down.
But we are Coder'y ...
Of course, it does not frighten us, we somehow place their
prog where it will not slow down. That's why I always
appreciated the Polish and Slovak programmers. Alone demo
SHOCK, which is where every stroke vymeryan, where we have
everything, but also that account is not possible. Of course,
everyone chooses his own path, and many may not care that
someone is not a Speccy, like yours. But it does not gloss over
your program.
Let's try to finish ...
That is to get small introduction
into this category. We look forward to your
letters and proposals. Maybe you want chtoto know, I will
gladly share with you. If nothing changed, then in the next
issue I will tell you about the secrets CPU Z-80. Believe me,
there is a very unique things, and that the branded
description is called undocumented
teams are not undocumented.
Just someone did not want to share, and
I found out, they were military.
And you, for example, know that the Z-80 is
Serial Interface? True, this function
processors integrate only Zilog, but
in any case it is unique.
Meet me in the next issue ...
