It is not clear where Bits and Chips got its information, but it claims AM4 will have 1,331 pins, which is a big increase over the 942 pins on the AM3+ socket. The package will be square, and 40 mm in length, making it about as big as a current socket FM2+ package. It will have a pin-count of 1,331 pins, a big increase from the 942 pins of AM3+, and 906 pins of FM2+. AMD could continue to develop LGA sockets for its multi-socket capable Opteron processors based on the "Zen" architecture.
The AM4 platform layout will be functionally similar to the FM2+ than the AM3+. Besides the integrated memory controller, the northbridge will be entirely located on the processor die. This means that the HyperTransport main system bus will be wired internally.
The AM4 pin-map will consist of memory I/O, integrated graphics I/O, PCI-Express, and the chipset bus and some other low-level system I/O interfaces. The memory controller on some of the first AM4 chips, such as "Summit Ridge," will natively support DDR4-2400 MHz, and DDR4-2933 MHz through overclocking.
AMD has used IMC standard designed by Synopsys to save some money. Due to low bandwidth DDR4, the magazine expects to see Zen APUs with HBM On Package .
The first AMD AM4 motherboards are expected to be out by the second quarter of this year.