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Intel 845G/845GL/845GV GMCH Chipset System Clock and AGP Cha

2016-02-19 14:00  
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The figure shows a block diagram of an 845G chipset-based system (enlarged click). The type of this series which isIntel 845G Chipset-Based System Clocking Diagramknown asIntel 82845G GMCH has the following clocks. There are:

• 100/133 MHz, Spread spectrum, Low voltage (0.7 V) Differential HCLKP/HCLKN for PSB
• 66.667 MHz, Spread spectrum, 3.3 V GCLKIN for hub interface and AGP
• 48 MHz, Non-Spread spectrum, 3.3 V DREFCLK for the Display frequency syntheses
• Up to 85 MHz, 1.5 V DVOBC_CLKINT for TV-Out mode

The AGP Electrical characteristicsshows that the 4X data transfers use 1.5 V signaling levels. Also, The GMCH supports 1X/2X/PCI data transfers using 1.5 V signaling levels. The table below shows the data rates and signaling levels supported by the GMCH:


Data RateSignaling Level 
 1.5 V3.3 V

The low voltage pins receive a host clock from the external clock synthesizer. The graphics engine uses this clock and so do the host interface and system memory logic.

The graphics core and display interfaces are asynchronous to the rest of the GMCH. The Graphics core runs at 200 MHz. The display PLL uses the Non-Spread Spectrum 48 MHz input to generate a frequency range of 12 MHz–350 MHz.

You can follow on completeIntel® 845G/845GL/845GV GMCH ChipsetwithSystem Clock and AGP Characteristicswithin in its Datasheet, just jump at page 137-138. (source: intel.com)