More Details about Rockchip RK3399Pro SoC, and RK1808 NPU

First announced in January 2018, Rockchip RK3399Pro was supposed to be a pin-to-pin compatible with Rockchip RK3399 processor, and adding a Neural-Network Processing Unit (NPU) capable of delivering 2.4 TOPS for acceleration A.I. workloads.

Shortly after Pine64 announced they’d be offering Rockpro64-AI board in August, and later on Vamrs unveils ROCK960 PRO at a Linaro Connect event with an expected Q2 2018 launch. But none of the RK3399Pro boards are available, as there have been delays with RK3399Pro, and some commented an external NPU would be launched first with further details.

But today – courtesy of Vamrs – we have some more details about RK3399Pro features, a likely explanation for the delay, and some information about Rockchip RK1808 NPU chip.

Contrary to the CES 2018 announcement, Rockchip RK3399Pro will come in a 27x27mm FCBGA1372 package instead of the 22x22mm FCBGA828 package for RK3399. So pin-to-pin compatibility is out of the windows, and boards will have to be designed specifically for RK3399Pro processors. Varms explains the NPU needs at least 512MB of dedicated RAM , and Rockchip may have first plans to pack a 512MB RAM using PoP technology, but due to overall (BoM) cost issues, they went with an external RAM interface instead. That change of direction would have required a redesign explaining the delay in getting the chip to market.

Beside the extra NPU chip, Rockchip RK3399Pro does away with one USB type C interface, and USB OTG1 interface.

RK3399Pro Edge AI Gateway Server — RK3399Pro Edge AI Gateway / Server

Rockchip expects the processor to be found into two main types of products: headless AI Edge gateways, or AI Edge devices with one or more displays. As I understand it, NDDR stands for NPU DDR, so RAM for the CPU and NPU is not shared, and that means RK3399Pro boards will be fairly larger. According to Vamrs it will not be possible to make a 96Boards CE compliant board, and instead they may have to use larger 96Boards CE Extended or 96Boards EE boards.

You’ll find the Linux 4.4 kernel code for RK3399Pro in Github, and interestingly there’s also another processor in the source: Rockchip RK1808 with two Arm Cortex A35 cores and an NPU as described in the device tree file.

cpus {
    #address-cells = <2>;
    #size-cells = <0>;

    cpu0: cpu@0 {
        device_type = "cpu";
        compatible = "arm,cortex-a35", "arm,armv8";
        reg = <0x0 0x0>;
        clocks = <&cru ARMCLK>;
    };

    cpu1: cpu@1 {
        device_type = "cpu";
        compatible = "arm,cortex-a35", "arm,armv8";
        reg = <0x0 0x1>;
        clocks = <&cru ARMCLK>;
    };
};
...
npu: npu@ffbc0000 {
		compatible = "rockchip,npu";
		reg = <0x0 0xffbc0000 0x0 0x1000>;
		clocks =  <&cru SCLK_NPU>, <&cru HCLK_NPU>;
		clock-names = "sclk_npu", "hclk_npu";
		interrupts = <GIC_SPI 43 IRQ_TYPE_LEVEL_HIGH>;
		status = "disabled";
};

cpus {

#address-cells = <2>;

#size-cells = <0>;

cpu0: cpu@0 {

device_type = "cpu";

compatible = "arm,cortex-a35", "arm,armv8";

reg = <0x0 0x0>;

clocks = <&cru ARMCLK>;

};

cpu1: cpu@1 {

device_type = "cpu";

compatible = "arm,cortex-a35", "arm,armv8";

reg = <0x0 0x1>;

clocks = <&cru ARMCLK>;

};

...

npu: npu@ffbc0000 {

compatible = "rockchip,npu";

reg = <0x0 0xffbc0000 0x0 0x1000>;

clocks = <&cru SCLK_NPU>, <&cru HCLK_NPU>;

clock-names = "sclk_npu", "hclk_npu";

interrupts = <GIC_SPI 43 IRQ_TYPE_LEVEL_HIGH>;

status = "disabled";

};

That’s interesting… So RK1808 should be the external NPU chip we’ve read about before… Further analysis of the dtsi file shows USB3, GMAC, and MIPI CSI/DSI/RGB interfaces, as well as 8x UART and 12-channel PWM which made Varms suspects the chip also targets industrial control and robotics markets.

There’s also a file called rk3399pro-npu.dtsi with the exact same CPU (2x Cortex A35) and NPU definitions, so it’s likely RK3399Pro SoC is just the original RK3399 processor connected to Rockchip RK1808 chip over a USB 3.0 interface.

Jean-Luc Aufranc (CNXSoft)

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.