In this article, I look inside a chip in the IBM 3274 Control Unit.1 But before I discuss the chip, I need to give some background on mainframes. (I didn't completely analyze the chip, so don't expect a nice narrative or solid conclusions.) Die photo of the Motorola/IBM SC81150 chip. Click this image (or any other) for a larger version. IBM's vintage mainframes were extremely underpowered compared to modern computers; a System/370 mainframe ran well under 1 million instructions per second, while...