than the three in the 1130. Another of its mini-like features was the extensive support for indirect addressing on most instructions. Many instructions require data to be read from a location in memory, in most CPUs of the era that would be a single byte of data that is stored in memory referred to by a 16-bit location. In the 2650, the high-bit of that 16-bit location indicated indirection, meaning that the data was not located at this location in memory, but the one encoded in the remaining 15 bits of the address. This style of access allowed blocks of data to be more easily accessed than in systems that provided indirection solely through special instructions or solely through index registers. One could step through memory by incrementing the address value stored in memory. This also resulted in considerable numbers of math instructions being applied to addresses, and to improve the performance of these operations, the 2650 included a second arithmetic logic unit just for address calculations. The downside to this approach was that the high-bit was no longer part of the address, meaning the address space was only 15 bits, and the machine could access only a total of 32 KB of memory. The address space was further limited by the use of another two bits of the address to indicate the indexing mode for all logical and arithmetic (i.e. non-branch) instructions. These bits controlled functions like whether the address should be post-incremented or pre-decremented, which is extremely useful for constructing loops. But with all of these bits already accounted for, only 13 were available for addresses in these instructions, meaning only 8 KB could be addressed directly. This meant the main memory was broken up as four 8 KB blocks. To access memory outside the 8 KB where the instruction was located, the data bytes being pointed to had to contain an indirect address, pointing to some other location in memory. Doing so forced another memory read cycle, slowing performance. When the 2650 was designed in 1972, these limitations on address space were not significant due to the small size and high cost of the static RAM memory typically used with these processors. At the time, machines typically contained 2 or 4 KB of RAM. But with the increasing use of dynamic RAM from the mid-1970s, machines with 8 and 16 KB of RAM, and ultimately 64 KB,