Forum - The concept of a high-color screen resolution.

<b>Forum</b> - The concept of a high-color screen resolution.

   We decided to also offer
the concept of high color screen resolution. It is not
implementation of this device
and supply circuitry
who can do it. As
we all know, the resolution of a standard screen on Spectrum'e
256x192x16. We propose to implement a microprocessor based on 
the second screen with the following parameters: 

a) 320x200x16 (256,65536 colors)
b) 640x400x16 (256 colors)
a) 640x480x16 (256 colors)


   These options will make great programs (both system and 
game). 

   To implement this resolution, we suggest the following. The 
microprocessor for the screen should operate at 15

MHz. It is necessary for the implementation of
the latter two modes, as for
This requires transfer of large data sets. At the same time
necessary to implement support for text mode, not leaving 
graphics. You can do this implement a small RAM

font in which to initialize the font will be recorded.
It can then be changed
if necessary. We also
propose for this
Screen realize ROM, which will contain the main program of the 
on-screen memory version of this ROM. It is also necessary to 
realize the direct appeal to the memory for the needs of 
programmers. Relationship with the screen can be performed 
through ports. It is also necessary to leave the old screen for 
the early programs, to be used as

screen buffer for the new.

   And now more specifically to
each issue.

   To begin explain why
choose these modes.
Firstly, because it will be easier to dock with different
images, filmed with an IBM-compatible computers. Secondly,
All these regimes can be put on
screen monitor or TV,
as size of the screen vertically
the TV is 625
rows of which are visible only 575.

   To ensure that all video modes will need the following RAM 
capacity: 

a) 320x200x16 - 32000 bytes

   320x200x256 - 64000 bytes

   320x200x65536 - 128000 bytes

b) 640x400x16 - 128000 bytes

   640x400x256 - 256000 bytes

a) 640x480x16 - 158600 bytes

   640x480x256 - 307200 bytes


   This can be implemented as follows: The user can gradually 
build up videoOZU at will, and ROM, located

The board will determine the capacity of installed RAM and, 
accordingly, allow the screen resolution. That is, if on a map 
for example, established 128 KB, it possible to display a

resolution of 320x200x16 (256,
65536 colors) and 640x400x16, and
other modes are closed for treatment. When attempting to use 
banned regimes ROM will generate an error for which the program 
determines she can continue working or not. Ability to transfer 
data from screen buffer can be arranged through direct access to

memory. You can implement more than one channel DMA to be used 
for other extensions.


   Accessing videoPZU can
arranged through a
address the standard ROM.

   To implement the 65536 colors,
if they are needed, you can use the DAC to convert the digital 
representation color to an analog signal.


   In videoPZU will, for example,
contain routines for drawing various geometric shapes, shading, 
contour, etc., which must be bystrorabotayuschimi. In this 
case, should videoPZU will work independently,

ie computer must be running in
multi-tasking, which will increase system performance.
You can also arrange access
directly to videoOZU.

   It will be necessary to introduce
of the ROM program output
screen videos are stored in
MPEG format or the like,
ie maintain the distinction between
two frames, and the rest discarded.

   VideoOZU can be arranged
pages, because with 128 KB can have two
pages with a resolution 320x200x
256 or four pages with a resolution of 320x200x16. Organization
pages can be organized
at IBM, that is, as follows:

   For example, enabled 320x
200x16. Get 4 bits per pixel. From each page is taken
only one bit and to get four bits, it is necessary
have 4 pages, and received 16
flowers on the spot. This allows
reduce the size of memory that must have immediate access that 
the use of Z80 is impossible, since Memory Size in high 
definition will be more than 64 KB.


   We propose to use
As the second processor Z80,
but you can use and more
productive Z80H, because he
operates at a higher frequency and has recourse to 512 KB of 
memory. In the first If there is a chance more

rapid failure of the microprocessor, because frequency is 4 
times the nominal rate. But we suggest that frequency, based on

from experiments conducted by one of
Readers ZX-Revue.

   When using this screen would be no need to
Programming MULTICOLOR'a,
there will be programs that are not inferior in quality of 
graphics programs on more powerful computers. But it will have 
to decide problems of speed, because can not

enough speed for pumping
video.

   Those who enjoy these ideas,
can write their ideas
at:


   142214 Serpukhov, ul.Podolskaya, d.107, kv.57.


   or contact:


   142214 Serpukhov, Sovetskaya St., d.102, kv.44.


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