The designers also wanted to add extra items to the PCB, so PCB space to put the additional parts was an important consideration. The previous Compute Module 3 has tracks carrying signals from one side of the SoC to the pins on the edge connector. These tracks take up valuable PCB space, preventing components being fitted there. We could add extra PCB layers to move these tracks from an outer layer to an inner layer, but these extra layers add to the cost of the product.
“We knew we wanted to get the extra features of the BCM2711 out to the connector so that users could make use of them in their products,” said Plunkett. “High-speed interfaces like PCIe and HDMI are so fast coming out of the BCM2711 that they need special IO pins that can’t also support GPIO: if we were to change the functionality of a GPIO pin to one of the new high-speed signals, this would break backwards compatibility.
The board is based on the same 1.5GHz 64-bit quad-core BCM2711 application processor as Raspberry Pi 4 to provide more performance for embedded designs.
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