181 lines
3.9 KiB
HTML
181 lines
3.9 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML
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><HEAD
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><TITLE
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>Memory Requirements</TITLE
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NAME="GENERATOR"
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TITLE="X.org/XFree86 Video Timings HOWTO"
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HREF="index.html"><LINK
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TITLE="Tradeoffs in Configuring your System"
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HREF="tradeoffs.html"><LINK
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REL="NEXT"
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TITLE="Computing Frame Sizes"
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HREF="framesizes.html"></HEAD
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>X.org/XFree86 Video Timings HOWTO</TH
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WIDTH="10%"
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>Prev</A
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><DIV
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CLASS="sect1"
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><H1
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><A
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NAME="sizes"
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></A
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>9. Memory Requirements</H1
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><P
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>Available frame-buffer RAM may limit the resolution you can
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achieve on color or gray-scale displays. It probably isn't a factor
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on displays that have only two colors, white and black with no shades
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of gray in between.</P
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><P
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>For 256-color displays, a byte of video memory is required for each
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visible dot to be shown. This byte contains the information that
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determines what mix of red, green, and blue is generated for its dot.
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To get the amount of memory required, multiply the number of visible
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dots per line by the number of visible lines. For a display with a
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resolution of 1024x768, this would be 1024 x 768 = 786432, which is
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the number of visible dots on the display. This is also, at one byte
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per dot, the number of bytes of video memory that will be necessary on
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your adapter card.</P
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><P
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>Thus, your memory requirement will typically be (HR * VR)/1024
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Kbytes of VRAM, rounded up (it would come to 768K exactly in this
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example). If you have more memory than strictly required, you'll have
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extra for virtual-screen panning.</P
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><P
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>However, if you only have 512K on board yor video card, then you won't
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be able to use this resolution. Even if you have a good monitor,
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without enough video RAM, you can't take advantage of your monitor's
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potential. On the other hand, if your SVGA has one meg, but your
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monitor can display at most 800x600, then high resolution is beyond
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your reach anyway (see <A
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HREF="inter.html"
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>Using Interlaced Modes</A
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>
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for a possible remedy).</P
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><P
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>Don't worry if you have more memory than required; the X server
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will make use of it by allowing you to scroll your viewable area (see
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the Xconfig file documentation on the virtual screen size parameter).
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Remember also that a card with 512K bytes of memory really doesn't
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have 512,000 bytes installed, it has 512 x 1024 = 524,288
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bytes.</P
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><P
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>If you're running X/Inside using an S3 card, and are willing to live
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with 16 colors (4 bits per pixel), you can set depth 4 in Xconfig and
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effectively double the resolution your card can handle. S3 cards, for
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example, normally do 1024x768x256. You can make them do 1280x1024x16
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with depth 4.</P
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>Prev</A
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>Home</A
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HREF="framesizes.html"
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>Next</A
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></TD
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></TR
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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>Tradeoffs in Configuring your System</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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> </TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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>Computing Frame Sizes</TD
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></TR
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></TABLE
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></DIV
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></BODY
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></HTML
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> |