Browse Prior Art Database

Tile Interleave in Random Access Memory Digital to Analog Converter

IP.com Disclosure Number: IPCOM000116247D
Original Publication Date: 1995-Aug-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Bowen, AD: AUTHOR

Abstract

With improvements to memory access speed, the time spent in fast page mode is becoming increasingly small, relative to the amount of time spent handling the accessing of new row addresses. In a system that renders vertical spans of data, this problem is accentuated. By allowing for alternate modes of swizzling in the Random Access Memory Digital to Analog Converter (RAMDAC)-- the device that accepts digital pixel data, formats, and generates the analog signals to the CRT--the overhead associated with accessing a new row of memory can be reduced or eliminated.

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Tile Interleave in Random Access Memory Digital to Analog Converter

      With improvements to memory access speed, the time spent in
fast page mode is becoming increasingly small, relative to the amount
of time spent handling the accessing of new row addresses.  In a
system that renders vertical spans of data, this problem is
accentuated.  By allowing for alternate modes of swizzling in the
Random Access Memory Digital to Analog Converter (RAMDAC)-- the
device that accepts digital pixel data, formats, and generates the
analog signals to the CRT--the overhead associated with accessing a
new row of memory can be reduced or eliminated.

      By allowing the memory banks to be segmented into two groups, a
nested interleave can be fashioned.  This interleave allows the frame
buffer controller to access the two groups of memory independently,
and remove the associated penalty of crossing the row boundary.  For
example, if there are 4 banks of memory, A,B,C, and D; the two groups
can
be A and B, and the other C and D.  The banks are swizzled as
follows:
                         X= 0 1 2 3 4 5 6 7 8 9 . . .
               Y= 0      A B C D A B C D A B . . .
               Y= 1      B A D C B A D C B A . . .
               Y= 2      A B C D A B C D A B . . .
                  .      . . . . . . . . . . .
                  .      . . . . . . . . . .   .
                  .      . . . . . . . . . .     .
               Y=15      B A D C B A D C B A . ....