TargeT #06 18 марта 2000

Будущее Спектрума

listening to you? - Valeron to speculate about "what is missing Spectrum?"

                                              ____

                                             /
- - / / | - -

               Listen to you? / / / Valeron
- - / / - -

                                               /

                                              ***


                   What we have not enough.


    Hi, people! Again I waste your time by their ravings. But
 want to get worn out, and not with anyone.

    And the reason for idle talk is: the video mode of our 
favorite Speck.  At the dawn of the dawn, and someone may be in 
the midst,  platform in our postsovke loved to scratch the 
language on the topic  how many colors and many points in a row 
I would like to have on  Spectrum. Seriously reasoned from the 
pages of the then popular  electronic journals as desirable 
colors and tables  Drive - how much memory it eats. Cool it 
appeared almost  not all 128 kilobytes of the video. I was 
still quite green, was  read and admired his mouth agape: To 
what future awaits! 

    However, the added years of cynicism and skepticism, I 
realized how difficult  standard screen for one int transfer, 
no different  tricks with stekom not do, and even then not on 
all models  a number of passes, some ungodly slow down. Of 
course  Turbo mode is good, but in turbo mode to get double

 acceleration of the RAM is almost impossible (if I am mistaken 
-  do not hurt!), but the essence of something else: how much 
will be built this  screen memory? Even in turbo mode? Suggests 
itself:  conclusion: the screen should not take up much memory, 
but this too  Of course you can sporit.No matter how much we do 
not want to see  colors on the screen, we should remember about 
the performance  processor and so the video area should not be 
large. If  can still be reconciled with the fact that the 
screen is being transferred for 5-10  Mounting, the 
construction of such a screen in the memory will be  hideously 
long. I think you should not go beyond the double  size, so 
6912 + 6912 = 13824. Yes, of course, be  and take a whole page, 
16384 bytes, but if you have enough  patience to read till the 
end of this opus, you'll understand why  is 13,824.


    Make an extended color mode will not be easy, but this
 The situation as it is also not satisfied with one color on 
the familiarity and  one background greatly complicate the 
creation of color graphics, especially not  full screen. Well 
sprite 2 to 2 familiarity (that would be  maintain an overview 
of as much as possible the site map is selected  the smallest 
size of a sprite) skrolirovat pixel by pixel and save  Color? 
Need at least one more bitplan. This is not so  burdensome for 
the CPU and is completely acceptable from an aesthetic  point 
of view: while maintaining the system color / familiarity, 
which is very  convenient in terms of compactness of the video 
field, is obtained for 2  color and 2 background. The 
background is the background and will have to do the same,  but 
color - a real goldmine for gfx-maker. 

    Do not claim to originality of ideas, because the whole 
universe  evolves in a spiral, and certainly someone came into 
his head  something like that, but we should say it out loud.


    So, the idea itself was formed when we had to
 enjoy shaking saver when each interrupt
 switches 5 and 7 pages of memory in the video field. Jitter
 of course on your nerves, but the picture obtained cute.
 RAGE such tricks are often used. If you remove the jitter - 
that  you additional bitplan. What comes to mind on this

 about it? You can make as General Sound with a separate 
processor  and his memory, but you need to do a little blood, 
the cost of  General Sound played, in my opinion, rokovyyu role 
in  rasprostronenii this rulnogo devaysa. Our device must

 be cheap, accessible to all, otherwise little chance of getting
 rasprostronenie, and accordingly it will not support
 programmers, and it will remain useless bloat.

    The second way - to intervene in the work of the video 
processor and  to form a screen with two pages. In my not the 
best way  because in the different components of video 
processor is implemented on  way. But judging from the Baltic 
Sea, it turns out very  tempting to try to switch the memory 
page from the fifth to  seventh in a time when the video 
processor selects bytes  screen. There should clarify what I 
mean. In the Baltic  processor receives a command waiting on 
line when the WAIT  display area becomes video processor. On 
the memory bus  appears low byte of the address attributes in 
the next step of this  B is taken into the internal register 
register RU'shek and on the bus  fed the high byte of 
attributes. In the next step of this  bytes received RU'shkami, 
and then in the next cycle of RU'shek  read data byte in a 
register that is implemented on a separate  chip. If not now 
awaiting arrival of the next  clock pulse to change one bit 
address corresponding to the number of  page to signal CAS to 
record the resulting new  high byte of Ru'shki and then read 
from RU'shek bytes of data  in another register, which will 
implement additional  soldered another chip IR27, then we 
obtain two separate  attribute byte corresponding to the same 
position of the screen.  Further, in the same way we proceed 
with the byte data screen  which is chosen in subsequent 
cycles. So we get two bytes  attributes and two bytes of screen 
data. Now we only need  bring them to release the video. To do 
this, you can simply  Duplicate the appropriate chip in the 
Baltic Sea is a KP15 and  two KP12, and a total of three 
registers IR27 obtained only  six cases. The trouble is that 
I'm not sure that such an approach  work, I have no job 
descriptions for RU5 and I do not know where  How often you can 
access them. 

    The third way - not the most elegant, but it seems to me 
the most  acceptable. Need to preserve the image of the screen 
say the fifth  page, and mix it with the image of the seventh 
page in memory. 

    How it will look.

    Video processor every fiftieth of a second begins
 sample screen of the video area. For once chosen a
 bytes. This byte is written into an intermediate register
 implemented on a separate mikruhe. Further into the different 
components of  differently, some take it multiplexers, in 
others -  shift registers, it is not so important - most 
important of which  This register can take the byte and treat as

 want.

    So, the idea that would save the byte in a separate
 mikruhe memory. Take mikruhu dynamic memory, such as
 RU17 to 8 kilobytes. Screen attributes requires 6,912 bytes,
 quite fit into our RUshke. This will be the screen buffer.

    Now when selecting a video processor bytes of screen memory

    should be considered in our RUshki bytes and store in a 
separate  register, and at this place in RUshku record only 
that the seized  video processor bytes. Now we have two display 
bytes  can impose a bit of both at each other

 respective colors inc and paper.

    Until switch pages 5 and 7 in the video field
 computer, of course, B will be the same, but if the same
 start now everyone int switch screens from fifth to seventh
 and back, then we can get nedrozhaschee (!) image.

    Well, let's say in a normal spektume display byte is taken
 bit at a time and in the light-colored dot on the screen is 
formed  image is then fed to the video output. We now need to

 replicate the process and parallel process in exactly the same
 read the second byte, and the stage of formation of the screen
 picture mix bits of logic "OR". Can be different:
 to form a point image of the first byte of its own, from the 
second  - Their own, and then, when it will be supplied to the 
video output -  mixed signals. Since the video output are 
generally  divider resistors, we can offer such a scheme in 
which  changes koofitsient division and then you can get a 
double  brightness for a single color or shades of the new 
mixing  for example purple and yellow for example. You can even

 separate register set koofitsienty division for each color
 and thereby set the palette image. You can make two
 separate register and set the palette for each of the two
 bitplanov. How do you like this: 16 colors from a palette of 
256? And given  poluyarkosti Bright - twice.


    Now the bitter. This design does not allow output
 animation at 50 frames per second, namely the old sprite
 will be superimposed on the new and the screen will stretch 
the tail  for a sprite. Although it is possible to offer the 
option of constructing  sprite, when we say the body appears in 
the fifth page, and  feet in the seventh. Then, changing 
alternately in the fifth then the seventh  page of sites you 
can get normalnyuyu sprite animation. In  this regard, this 
option is less convenient than the other way  which I described 
above. 

    All the above is a crude idea, and not backed
 any experiments, any attempt to implement this on
 practice has not yet been undertaken, unfortunately, all that 
I write  that would share with the people concerned with their 
ideas. 

    And finally, who it can create in the gland. Should you
 upset, but I can not. Maybe someday I will achieve this
 level, but so far I've only dissect and Bytes
 Baltic Sea, and the map needs a universal, for any company. 
And in  alone to develop such a device itself, you will agree, 
is difficult.  In any case, I will be glad if someone 
zaiteresuetsya this idea. 

 16.09.1999

 FOX> So, Valeron gave his point of view. You can not disagree
 that the Spectrum screen leaves much to be desired. However,
 no one has yet solved this problem. Why? Maybe it is not
 really? May be needed to finally admit that Spektrumeto
 Spectrum and not try to make him God knows what? Maybe
 be still needed to look for? After all, who are looking for, 
he finds! Like  to hear your thoughts! E-mail us!