Intel 440GX manual 4. Four Layer Board Stack-up, Motherboard Layout and Routing Guidelines

Motherboard Layout and Routing Guidelines

Figure 2-4. Four Layer Board Stack-up

Z = 60 ohms

Z = 60 ohms

Primary Signal Layer (1/2 oz. cu.)

	5 mils	PREPREG
				Ground Plane (1 oz. cu.)
47 mils			CORE
				Power Plane (1 oz. cu)
	5 mils	PREPREG
				Secondary Signal Layer (1/2 oz. cu)

Total board thickness = 62.6

Note: The top and bottom routing layers specify 1/2 oz. cu. However, by the time the board is plated, the traces will end about 1 oz. cu. Check with your fabrication vendor on the exact value and insure that any signal simulation accounts for this value.

Note: A thicker core may help reduce board warpage issues.

For a dual processor / Intel® 440GX AGPset design, a 6 layer stack-up is recommended. Two examples are shown below. Figure 2-5has 4 signal plane layers and 2 power plane layers.

Figure 2-6shows 3 signal plane layers and 3 power plane layers. The second option makes it easier to accommodate all of the power planes required in a Intel® 440GX AGPset design.

If a 6 layer stack-up is used, then it is recommended to route most of the GTL+ bus signals on the inner layers. The primary and secondary signal layer can be used for GTL+ signals where needed. Routes on the two inner layers should be orthogonal to reduce crosstalk between the layers.

Figure 2-5. Six Layer Board Stack-up With 4 Signal Planes and 2 Power Planes

Z = 66 ohms Primary Signal Layer (1/2 oz. cu.)

		6 mils	PREPREG
					Ground Plane (1 oz. cu.)
	18 mils			CORE
Z = 73 ohms					Inner Layer #1 (1 oz. cu.)
		6 mils	PREPREG
					Inner Layer #2 (1 oz. cu)
	18 mils			CORE
					Power Plane (1 oz. cu)
		6 mils	PREPREG
Z = 66 ohms					Secondary Signal Layer (1/2 oz. cu)

Total board thickness = 62.4

2-4 Intel®440GX AGPset Design Guide