Ckbf Sdram 1 to 18 Clock Buffer

Design Checklist

3.4.2CKBF - SDRAM 1 to 18 Clock Buffer

•A 4.7K ohm pull-up to VCC3.3 on the OE pin is needed to enable the buffer.

•Note that DCLKRD pin has been changed to a no connect (NC). The DCLKRD functionality has been combined with DCLKWR. If desire to remove the trace going to DCLKRD pin, the capacitor value should be adjusted to compensate for the capacitance change.

•An I2C interface is provided which allows the BIOS to disable unused SDRAM clocks to reduce EMI and power consumption. It is recommended that the BIOS disable unused clocks.

•No series termination is required for the SDRAM clocks between the CKBF and the DIMMs.

•DCLKO from the 82443GX to the CKBF should have a 22 ohm series resistor placed at the 82443GX, and a 47 ohm series resistor placed at the CKBF. This has been shown in simulations to improve the signal integrity of this signal.

•Check with your clock vendor and the reference schematics for special layout and decoupling considerations. The reference schematics implement an LC filter on the supply pins to reduce noise.

3.4.3GCKE and DCLKWR Connection

•See the diagram below for implementation of the 16-bit flip-flop for CKE generation for 4 DIMMs.

•GCKE trace length from the 82443GX to the flip-flop is recommended to be 1” MIN to 4” MAX. CKE trace lengths from the flip-flop to the DIMMS is recommended to be 3”.

Figure 3-2. GCKE & DCLKWR Connections

D C L K W R NC (AB22)

G C K E

82443GX

G N D

C K B F

		27pF
				1 D 1
				1 D 1
				1 D 2
				1 D 3
	20pF			1 D 4
	20pF			1 D 5
				1 D 6
				1 D 7
				1 D 8
				2 D 1
- Clock signals fed back into 82443GX and				2 D 2
- Clock signals fed back into 82443GX and				2 D 3
D-FF must ‘T’-off with equal trace length				2 D 3
D-FF must ‘T’-off with equal trace length				2 D 4
and as close as possible to the 82443GX and				2 D 4
and as close as possible to the 82443GX and				2 D 5
D-FF.				2 D 5
D-FF.				2 D 6
- The capacitors must be placed close to			the	2 D 6
- The capacitors must be placed close to			the	2 D 7
node where the clock signals are ‘T’-ed.				2 D 7
node where the clock signals are ‘T’-ed.				2 D 8
- The capacitor values are shown.				2 D 8
- The capacitor values are shown.

1EN

2EN C 1 C 2

7 4 L V C H 1 6 3 7 4

1 Q 1	C K E 7
1 Q 2	1D3, 1D4
1 Q 3	C K E 6
1 Q 4	1D5, 1D6
1 Q 5	C K E 5
1 Q 6	1D7, 1D8
1 Q 7	C K E 4
1 Q 8	2D1, 2D2
2 Q 1	C K E 3
2 Q 2	2D3, 2D4
2 Q 3	C K E 2
2 Q 4	2D5, 2D6
2 Q 5	C K E 1
2 Q 6	2D7, 2D8
2 Q 7	C K E 0
2 Q 8
	v007

NOTES:

1.The above circuitry only applies to unbuffer DIMMS. GCKE needs to be disabled for register DIMMS.

2.Pin AB22 has been changed to a no connect (NC), The 82443GX does not have an internal connection for pin AB22. Existing designs connected DCLKWR & AB22 nets on the motherboard. Since the 82443GX does not have an internal connection for pin AB22, it will cause a slightly reduced load capacitance on the net. To avoid additional clock skew on existing designs, a discrete capacitor larger than the 20pF capacitor recommended may be required.

Intel®440GX AGPset Design Guide

3-9

440GX specifications

The Intel 440GX chipset was launched in 1997 as part of Intel's series of chipsets known as the 440 family, and it served as a critical component for various Pentium II and Pentium III-based motherboard architectures. Specifically designed for the second generation of Intel’s processors, the 440GX delivered enhanced performance and supported a range of important technologies that defined PC architectures of its time.

One of the main features of the Intel 440GX was its support for a 100 MHz front-side bus (FSB), which significantly improved data transfer rates between the CPU and the memory subsystem. This advancement allowed the 440GX to accommodate both the original Pentium II processors as well as the later Pentium III chips, providing compatibility and flexibility for system builders and consumers alike.

The 440GX chipset included an integrated AGP (Accelerated Graphics Port) controller, which supported AGP 2x speeds. This enabled high-performance graphics cards to be utilized effectively, delivering many enhanced graphics capabilities for gaming and multimedia applications. The AGP interface was crucial at the time as it offered a dedicated pathway for graphics data, increasing bandwidth compared to traditional PCI slots.

In terms of memory support, the 440GX could address up to 512 MB of SDRAM, allowing systems built with this chipset to run comfortably with sufficient memory for the era’s demanding applications. The memory controller was capable of supporting both single and double-sided DIMMs, which provided versatility in memory configuration for system builders.

Another notable feature of the Intel 440GX was its support for multi-processor configurations through its Dual Processors support feature. This allowed enterprise and workstation computers to leverage the performance advantages of multiple CPUs, making the chipset suitable for business and professional environments where multitasking and high-performance computing were essential.

On the connectivity front, the chipset supported up to six PCI slots, enhancing peripheral device integration and expansion capabilities. It also included integrated IDE controllers, facilitating connections for hard drives and CD-ROM devices.

Overall, the Intel 440GX chipset represented a balanced combination of performance, flexibility, and technology advancements for its time. Its introduction helped establish a foundation for subsequent advancements in PC technology and set the stage for more powerful computing systems in the years to come.

Intel 440GX manual Ckbf Sdram 1 to 18 Clock Buffer, Gcke and Dclkwr Connection

Models: 440GX