Difference between revisions of "VRAM"

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In the [[Channel F]], VRAM is a 128x64 pixel ( 8192 x 2 bits / 2kByte ) portion of RAM in the console, that can only be accessed through the [[CPU ports|port]]s. A portion of this VRAM is used as the display on the television screen. Column 125 and 126 controls the [[palette]] for the row of VRAM it is written on. The rest of the VRAM is unused by the console, it can be written to but there's no way of reading it back, there's however [[Schach RAM]] available in some cases depending on your cartridge platform.
 
In the [[Channel F]], VRAM is a 128x64 pixel ( 8192 x 2 bits / 2kByte ) portion of RAM in the console, that can only be accessed through the [[CPU ports|port]]s. A portion of this VRAM is used as the display on the television screen. Column 125 and 126 controls the [[palette]] for the row of VRAM it is written on. The rest of the VRAM is unused by the console, it can be written to but there's no way of reading it back, there's however [[Schach RAM]] available in some cases depending on your cartridge platform.
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Regarding the hardware the DRAM is usually Fairchild's own with their own markings, it's a MK4027 compatible DRAM in the first generation of machines (built-in speaker) and a MK4015N compatible DRAM in the second generation (VLSI circuits). Good to know if you're looking for spare parts in case you have odd colored bars in your display.
  
 
The portion of VRAM which is displayed starts at column 4, row 4 and expands 102 pixels horizontally and 58 pixels vertically, giving a resolution of 102x58 pixels. This resolution is used in the original release of the MESS emulation system. However, most televisions display a smaller resolution horizontally, so more accurately the resolution of the Channel F is about 95x58 pixels. <br><br><br>
 
The portion of VRAM which is displayed starts at column 4, row 4 and expands 102 pixels horizontally and 58 pixels vertically, giving a resolution of 102x58 pixels. This resolution is used in the original release of the MESS emulation system. However, most televisions display a smaller resolution horizontally, so more accurately the resolution of the Channel F is about 95x58 pixels. <br><br><br>

Revision as of 15:17, 2 July 2013

In the Channel F, VRAM is a 128x64 pixel ( 8192 x 2 bits / 2kByte ) portion of RAM in the console, that can only be accessed through the ports. A portion of this VRAM is used as the display on the television screen. Column 125 and 126 controls the palette for the row of VRAM it is written on. The rest of the VRAM is unused by the console, it can be written to but there's no way of reading it back, there's however Schach RAM available in some cases depending on your cartridge platform.

Regarding the hardware the DRAM is usually Fairchild's own with their own markings, it's a MK4027 compatible DRAM in the first generation of machines (built-in speaker) and a MK4015N compatible DRAM in the second generation (VLSI circuits). Good to know if you're looking for spare parts in case you have odd colored bars in your display.

The portion of VRAM which is displayed starts at column 4, row 4 and expands 102 pixels horizontally and 58 pixels vertically, giving a resolution of 102x58 pixels. This resolution is used in the original release of the MESS emulation system. However, most televisions display a smaller resolution horizontally, so more accurately the resolution of the Channel F is about 95x58 pixels.


screenshot from MESS displaying the visible and invisible portions of VRAM

screenshot of normal size, videocart 5

A screenshot from MESS displaying both the visible and invisible parts of VRAM, the other one shows a screen of normal size in approx. the same scale.

See Also