L2Mersit: A Scaling-Free Sub-8-bit Data Format for On-Device Reliable Large Language Model Serving
On-device large language model (LLM) serving drives low-precision computing to address memory and compute limits. This paper presents L2Mersit, a scaling-free, range-adjustable exponent-encoded data format tailored for sub-8-bit LLM quantization. Building upon the Mersit framework, L2Mersit employs dual mode operation, comprising range-expanded and precision-enhanced modes that dynamically adapt to activation distributions with minimal control overhead. The proposed design eliminates on-the-fly scaling and auxiliary computations while effectively preserving range and precision, thereby achieving both superior perplexity and hardware efficiency. Experimental results demonstrate that L2Mersit achieves the highest accuracy among all 6-bit exponent-encoded formats while reducing the hardware complexity of auxiliary units for low-precision computing, resulting in a 62.7% area reduction.