Definition
Transistor density measures how many transistors a process can pack into a given area of silicon, most often expressed in MTr/mm² (millions of transistors per square millimeter). It has become a more honest figure of merit than the marketing "nanometer" node name, which no longer corresponds to any physical dimension. For Bitcoin mining ASICs, higher density means more hashing logic per square millimeter of expensive wafer, which is central to cost and efficiency.
How it is measured
Because real chips mix many cell types, a standardized density metric, popularized by Intel, combines the density of a common 2-input NAND gate with that of a more complex scan flip-flop, weighting them to approximate a realistic logic layout. The metric deliberately excludes SRAM, since the ratio of memory to logic varies enormously between designs and would otherwise distort comparisons between processes.
Why the node name lies
Two different foundries' "3nm" processes can have noticeably different MTr/mm² figures, so density is the fairer way to compare them. Leading nodes now reach into the hundreds of millions of transistors per square millimeter. Denser logic lets a mining chip fit more SHA-256 cores per die, but it also concentrates heat, so density gains must be balanced against the power-delivery and cooling limits that govern real-world joules per terahash.
Transistor density rises with each shrink of the FinFET and GAAFET, and it is the practical yardstick by which Moore's Law is tracked today.
In Simple Terms
Transistor density measures how many transistors a process can pack into a given area of silicon, most often expressed in MTr/mm² (millions of transistors per…