POWER GXT150L ??? FRU 88G2479 Feature 2660

J1 13W3 video
J2 Local bus header
U1-12 KM428C257T-6
U27 8187135 Pallete DAC
U30 88G2562
U32 88G2832
U35 88G2832
U38 50.0000 MHz osc
U40 66.0000 MHz osc

S36 Switch Positions

Louis: I tried to tabulate the GXT150L/155L switch settings, but it's too complex. So Ask Me for the GXT150L Switch Settings (PDF)

POWER GXT150L Graphics Adapter

This graphics adapter is designed for superior 2D performance in an AIXwindows 2D environment.
   The POWER GXT150L graphics adapter is an 8-bit single buffer, 256-color, graphics adapter that attaches to the PowerPC 601 local bus graphics expansion slot and does not use a Micro Channel slot. When used in conjunction with the AIXwindows 3D feature and Softgraphics, it provides cost-effective 3D performance. This is made possible through a design that interfaces video memory and a unique graphics accelerator chip directly to the PowerPC 601 local bus graphics expansion slot. The POWER GXT150L is similar to the previously announced POWER GXT150, but has been designed to fit into the larger graphics expansion slot in the RISC System/6000 Models 41T and 41W graphics workstations.
   The POWER GXT150L graphics adapter provides 1280x1024, 1152x900, and 1024x768 resolution support, three color palettes, and hardware window support.
   The POWER GXT150L requires AIXwindows Environment/6000 Version 1.2.5 2D (support for X11R5), or later, and AIX (R) Version 3.2.5 for RISC System/6000.  Refer to Software Announcement 293-489, dated September 21, 1993, for more details on AIXwindows and Softgraphics.


  • Low-cost, high-performance graphical interface acceleration
  • 2D hardware acceleration for:
    • Points
    • Lines
    • Triangles
    • Rectangles
    • Quadrilaterals
    • Bit block transfer
  • Pattern fill support
  • Rectangular and non-rectangular clipping
  • 60 to 77Hz refresh modes
  • 1280 x 1024, 1152 x 900, and 1024 x 768 resolution
  • 256 colors from a palette of 16 million
  • Three color palettes
  • Hardware window support
  • Meets ISO 9241 Part 3 on appropriate displays
  • Maximum of one adapter per system can be installed

The PAX 2D Rendering Engine (by Charles R. Johns and Taggart Robertson)

   Powerful processors and window managers have enabled application writers to exploit the power of graphics. This power has created increased pressure on workstation suppliers to provide high-performance graphics solutions to the entry level market segment. The POWERstation/POWERserver 250 series workstations along with the POWER GXT100 and GXT150 adapters provide such a solution.
   The POWER GXT100 and GXT150 are 2D graphics adapters based on the Pixel Accelerator for X (PAX) 2D rendering engine and the IBM RGB 530 Palette Digital to Analog Converter (Palette-DAC). The PAX engine draws or renders the graphical data sent from the 601 processor complex and the RGB 530 displays the data on the screen. The GXT100 is an entry-level adapter with memory to support a 1024 x 768 screen. The GXT150 has added memory to support up to a 1280 x 1024 screen and to utilize the multiple color palettes in the IBM RGB 530 Palette-DAC. Both the GXT100 and the GXT150 are 8-bit adapters which require AIXwindows Environment/6000 Version 1.2.5 2D and AIX Version 3.2.5.
   This article presents the design goals, a brief overview of the GXT100 and GXT150 graphics subsystem organization, a detailed look at the programming models, and the architecture of the PAX 2D rendering engine. This article describes the features and functions of the PAX rendering engine. All of these features and functions may not be exploited by the graphics subsystem.

Design Goals and Considerations
   The major goal of the PAX 2D rendering engine is to address the cost-performance requirements of the entry workstation market segment. Since X Window System is the predominant Graphical User Interface (GUI) on IBM workstations in this market segment, the architecture is dedicated to accelerating X Window applications. This goal, along with the considerations of time to market and cost, drove the architecture and design of the PAX 2D rendering engine. The architecture of a graphics subsystem can influence X Window performance and time to market in several areas. The PAX architecture targeted three areas: efficient interfaces, simple programming model, and rendering speed. Details of how each area is addressed appear in the following sections.

Graphics Subsystem Organization
   The POWER GXT100 and GXT150 consists of the PAX 2D rendering engine, the IBM RGB 530 Palette-DAC, 1M to 3M bytes of frame buffer memory, and the initialization Read Only Memory (ROM). Figure 1 shows the complete block diagram and the major interfaces of the graphics subsystem. The PAX chip serves as the graphics accelerator as well as the system interface for the adapter. It contains the control for accessing the initialization ROM, the Palette-DAC control port, and the video RAM (VRAM) parallel port. PAX attaches directly to the PowerPC 601 Microprocessor bus. Attaching directly to the PowerPC 601 bus improves performance by avoiding the latency and synchronization overhead created when converting from one bus to another. The 601 bus is a split address and data bus with 32 bits of address and 64 bits of data [1]. The processor uses byte, half-word, or word operations to access the graphics subsystem. Based on the address of the operation, PAX directs the access to one of four locations: the internal registers, the frame buffer (i.e. the VRAM), the RGB 530 Palette-DAC, or the initialization ROM.

Content created and/or collected by:
Louis F. Ohland, Peter H. Wendt, David L. Beem, William R. Walsh, Tatsuo Sunagawa, Tomáš Slavotínek, Jim Shorney, Tim N. Clarke, Kevin Bowling, and many others.

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