- Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing software that is rarely changed during the life of the system, also known as firmware. Software applications (like video games) for programmable devices can be distributed as plug-in cartridges containing ROM.
- Inside the ALU of the armv1 - the first ARM microprocessor (daveshacks.blogspot.com)
With that in mind I embarked on my own attempt to reverse-engineer parts of the armv1. Some background knowledge of the processor’s architecture is helpful, and googling for “ARM Architecture Reference Manual” will lead you to very detailed descriptions of the more modern versions of the processor. By just looking at the masks and knowing a little about the processor’s architecture it’s possible to make some good guesses at what some of the blocks are.