This paper proposes an innovative Floating Point (FP) architecture for Variable Precision (VP) computation suitable for high precision FP computing, based on a refined version of the UNUM type I format. This architecture supports VP FP intervals where each interval endpoint can have up to 512 bits of mantissa. The proposed hardware architecture is pipelined and has an internal word-size of 64 bits. Computations on longer mantissas are performed iteratively on the existing hardware. The prototype is integrated in a RISC-V environment, it is exposed to the user through an instruction set extension. The paper we provide an example of software usage. The system has been prototyped on a FPGA (Field-Programmable Gate Array) platform and also synthesized for a 28nm FDSOI process technology. The respective working frequency of FPGA and ASIC implementations are 50MHz and 600MHz. The estimated chip area is 1.5mm 2 and the estimated power consumption is 95mW. The flops performance of this architecture remains within the range of a regular fixed-precision IEEE FPU while enabling arbitrary precision computation at reasonable cost.