Las month, Olimex discovered a Chinese company called GigaDevice has made an STM32 clone called GD32 and compatible with STM32F103, but with higher core frequency (108MHz). Olimex has now posted an update after receiving a letter from GigaDevice, and trying GD32F103RBT6 MCU on their own STM32F103 boards. The company explained that GD32 was their own implementation, and claimed rights on GD32 trademarks, while Olimex discovered than GD32 was working just fine on their board having passed “all functional tests without any modifications”, and with all the same development tools and software code running fine.
GD32F103xx datasheet (PDF / English version) can be downloaded to find a few more details:
The GD32F103xx device incorporates the ARM Cortex-M3 32-bit processor core operating at 108 MHz frequency with Flash accesses zero wait states to obtain maximum efficiency. It provides up to 3 MB on-chip Flash memory and up to 96 KB SRAM memory. An extensive range of enhanced I/Os and peripherals connected to two APB buses. The devices offer up to three 12-bit ADCs, up to two 12-bit DACs, up to ten general-purpose 16-bit timers, two basic timers plus two PWM advanced-control timer, as well as standard and advanced communication interfaces: up to three SPIs, two I2Cs, three USARTs, two UARTs, two I2Ss, an USB 2.0 FS, a CAN and a SDIO.
The device operates from a 2.6 to 3.6 V power supply and available in –40 to +85 °C temperature range. Several power saving modes provide the flexibility for maximum optimization between wakeup latency and power consumption, an especially important consideration in low power applications.
Roger Clark also found out the board previously, and added support for GD32 to Arduino STM32. He also noticed that beside the fast clock speed, the zero wait state internal flash also provided performance improvements with GD32 delivering 64.41 VAX MIPS against 48.81 VAX MIPS when both MCUs are clocked at the same 72 MHz frequency.
The tests were done on the GD32F103 board above, which can be purchased for 15 RMB (~$2.3 US) on Taobao. I also looked for GD32 board on Aliexpress, but the MCU does not appear to be very popular outside of China, and I only found one $12.75 GD32 + WiFi board. If you are based in China you have more more choice here and there with evaluation boards with LCD displays selling for 281 RMB (~$44 US) and up. You can also purchase various version of GD32 MCUs directly for $0.70 to $2.80 on Taobao.
Visit GigaDevice GD32 product page for some more details.