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MediaGX



This Article was last modified in December, 1997.

The Cyrix MediaGX is a rather interesting processor, designed for extremely low-cost systems. The MediaGX processor incorporates multimedia and system functions right on the CPU. This new architecture helps PC manufacturers to deliver low-cost systems with the features and performance of much more expensive multimedia PCs.

The MediaGX System consists of two chips--the MediaGX processor and the MediaGX Cx5510 companion chip.

The audio and graphics functions of the two chips operate under the control of the Virtual System Architecture™ (VSA) design. This design also helps to eliminate system conflicts and end-user configuration problems.

The MediaGX processor is a 64-bit data bus, x86-compatible processor with a proven core. The CPU directly interfaces to a PCI bus and DRAM memory. SVGA graphics are provided by a graphics accelerator on the MediaGX processor. The graphics frame buffer is stored in main memory without the performance degradation associated with traditional Unified Memory Architecture (UMA) system designs due to Cyrix's new Display Compression Technology (DCT).

The companion chip, the MediaGX Cx5510, bridges the MediaGX processor over the PCI bus to the ISA bus, performs traditional chip-set functions, and supports a sound interface compatible with industry-standard sound cards.

Specifications

64-Bit x86 Processor
  • Performance at 133, 150, 166 and 180MHz
  • 16 KByte Unified L1 Cache
  • Unique Scratchpad RAM for SMM and Graphics
  • Integrated Floating Point Unit
  • Enhanced System Management Mode (SMM)

Power Management

  • Supports Cx5510 NoteBook Power Management
  • Private Link to Cx5510 for Monitoring
      System Activity

PCI Controller

  • Fixed, Rotating, Hybrid or Ping Pong Arbitration
  • Supports Four Masters (Three on PCI Bus)
  • Synchronous CPU/PCI Bus Frequency
  • Supports Concurrent CPU and PCI Operations

Additional Features

  • 352-Pin Ball Grid Array (BGA) Package
  • 0.5 micron, TLM CMOS Process
  • 3.3 to 3.6 Volt Operation
VSA Virtual VGA
  • Supports all VGA Modes
  • Faster than Many Hardware-Based solutions
  • Supports all VESA Modes
  • Accelerates BitBLTs, Line Draw, Text
  • Supports all 256 Raster Operations
  • Runs at Core Clock Frequency
  • Provides glueless TFT and RAMDAC Interface
  • Supports up to 1280 x 1024 x8 and 1024 x 768 x 16 BPP

Memory Subsystem

  • 64-bit EDO DRAM Controller
  • Tight Coupling to CPU Core
  • Runs at Core Clock Frequency
  • UMA Implemented with Video Compression
  • CAS Before RAS and Self Refresh Support
  • Provides Support for up to 128 MBytes in 4 Banks


MediaGX Processor

The MediaGX processor executes x86 instructions using a proven Cyrix CPU core, and also acts as a virtual video card. This chip provides a video port that connects directly to a flat panel or to an external RAMDAC chip for CRT display. The processor also provides a 64-bit wide DRAM interface and video compression which allows video and main memory sharing without memory performance degradation.

The MediaGX processor core operates from a 3.3 or 3.6 volt power supply, resulting in low power consumption at all clock frequencies. Where additional power savings are required (especially in portable applications), designers can make use of suspend mode, stop clock capability, and System Management Mode (SMM).

Other features include:

• Performance at 133, 150, 166 and 180MHz
•16-KByte Unified L1 Cache
• Integrated Floating Point Unit
• Enhanced System Management Mode (SMM)
• 64-bit FPM/EDO DRAM Controller

Major Functional Blocks
The MediaGX processor is made up of eight major functional blocks, as shown below:

• Execution Core
• Floating Point Unit
• L1 Cache
• Internal Bus Controller
• PCI Controller
• Graphics Pipeline
• Display Controller
• DRAM Controller

In general, data and code from DRAM or the PCI port travels over the X and C internal bus lines to the L1 cache where it is stored. Code instructions are fetched from the DRAM port or L1 cache by the execution core and floating point unit for processing.

Video data is processed by the graphics pipeline and video display controller. Output from the video display controller is sent to a CRT monitor (via a RAMDAC chip) or directly to a flat-panel monitor.

The PCI bus controller is used to control the PCI bus--there is no external CPU bus. The MediaGX Cx5510 performs functions such as interfacing to the IDE and I/O ports and the ISA bus.

Internal Bus Controller
The Internal Bus Controller provides a bridge between the C bus and the X bus. The bus controller provides configuration control for as many as 20 different regions in system memory with separate controls for read access, write access, cacheability and PCI bus access.

PCI Controller
The PCI Controller is a full-function PCI interface module that supports cache line bursting, pacing of data during both read and write operations, permits up to three PCI masters and uses three types of arbitration.

Graphics Pipeline
The Graphics Pipeline is GUI accelerator that includes a complete bitBLT/rendering engine and support for all three-operand boolean raster operations. The graphics pipeline, controlled by a set of Microsoft Windows 95 and NT drivers, provides adequate GUI performance. The drivers and graphics pipeline are closely coupled in unique ways and have the capability to perform high-speed block transfers between virtual memory and the frame buffer.

Display Controller
The Display Controller interfaces the MediaGX processor to display devices. It provides direct interfaces to converts host data to TFT (Thin Film Transistor) flat panel displays and to RAMDAC (Random Access Memory Digital to Analog Converter) for driving CRTs.

The display controller retrieves image data from the frame buffer, inserts cursor and icon overlays into the pixel stream, generates display timing, and formats the pixel data for output to a variety of display devices.

Virtual System Architecture™ (VSA) Technology
A unique combination of hardware and software in the MediaGX provides compatibility with VGA and VESA graphic standards. The graphics pipeline and display controller are hardware assisted to support many VGA and VESA data operations, but all the of the VGA registers and controls are virtualized through Cyrix's Virtual System Architecture (VSA) software.

VSA technology allows hardware to be replaced by software without sacrificing compatibility. Hardware to be virtualized is replaced with simple memory and I/O trapping hardware. When an application or non-Windows operating system attempts to access a VGA register or memory range, the MediaGX processor detects the access attempt and internally takes a System Management Interrupt (SMI) and enters into a System Management Mode (SMM).

When the MediaGX goes into SMM, it saves the processor state and invokes a VSA handler that determines the cause of the SMI. The VSA handler then calls a VSA graphics driver to process the graphics access. The handler and VSA driver run in a special SMM mode making operations completely transparent to the application and operating system.

While VSA technology provides full compatibility for all VGA and VESA modes and registers, the VSA graphic drivers take full advantage of the graphics pipeline boosting VGA performance in the MediaGX.

The MediaGX also uses VSA software to provide sound card compatibility.

CPU-Central Scoring

Overclockability ???
3D Performance 55%
Overall Performance 85%
Upgradability 0%
Compatibility 75%
Price 95%

Overclockability: I've never heard of anyone overclocking a MediaGX, and I haven't ever done it myself, so I can't really give it a score. If anyone has any information on overclocking this type of chip, please e-mail me.

3D Performance: As in the 6x86 and 6x86MX, the FPU performance of any Cyrix CPU (so far) is very weak, and this leads to slower performance in FPU intense software, such as Quake.

Overall Performance: The MediaGX is about as fast as its' equivalent Pentium Processor in business applications, however, in 3D applications, the MediaGX performs adequately, but not near as well as any Pentium.

Upgradability: Since these MediaGX processors are integrated right on to the motherboard, it doesn't leave any room for upgrading.

Compatibility: Since almost all PC games and applications are fine tuned for Pentium CPU's, the MediaGX suffers some problems with some specific software. Cyrix has come out with patches to fix many of the problems which can be downloaded from their website.

Price: The MediaGX is an excellent value for the processor, sound, and video card that you get. I would definately recommend this chip for anyone on a tight budget.

OVERALL SCORE: 75%

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