BIOS flash chip from an Apple iBook Clamshell that tried to sneak into my dorm room sophomore year. Didn't survive ;)
Datasheet: “Flash Memory 8Mbit (512Kbitx16 / 1Mbitx8)”
Size is approximately 6410 x 5580 μm (35.76 mm2).
Die revision markings and test structures
Address grid markings on main flash array.
Logic in upper left, focus on poly
Same area, focus on M1
Same area, focus on M2
Looked like CMP filler over SRAM at first, but now seems to be NOR mask ROM given the non-repeating pattern.
16 bits per column x 16 columns = 256 bits. 3 μm vertical bit pitch, 386 μm high = 128 bits high. 32kbits = 4KB.