If you need a reliable USB-bootable MIPS platform, consider a router (e.g., Xiaomi R3G) with U-Boot + USB boot support via pb-boot or breed bootloader.
The GX6605S is a budget-oriented, low-power system-on-chip (SoC) designed by Goke (mainly for Chinese digital TV receivers, set-top boxes, and embedded Linux devices). It is based on a single-core 32-bit MIPS 24Kc architecture (similar to early MediaTek WiSoCs). It lacks a traditional PC BIOS, instead using a vendor-specific boot ROM and a proprietary bootloader stored in NAND or SPI flash. gx6605s usb boot