128 KB Flash, 64 KB SRAM — memory sizing for the firmware budget
The 128 KB Flash is organized as 128K x 8, typical for mid-range Cortex-M3 parts of this generation. The 64 KB SRAM (64K x 8) is the standout: many competing MCUs at the same price point offered 32 KB or 48 KB. That extra SRAM headroom matters when the application runs a USB stack, a small RTOS, and a communications protocol simultaneously — the memory map can hold the stack and heap without thrashing. For designs that need to log sensor data or buffer serial streams, the 64 KB SRAM reduces the need for an external serial SRAM or FRAM.
No stock or lead-time number is published here because the spot market for an obsolete MCU moves week to week. If your design can accept a pin-compatible alternate, the LM3S3749 family includes other speed and memory variants in the same 100-LQFP footprint — but no direct replacement is listed on the official record.