Oh, the old days. I used a Model 67 at college. The first paragraph in Wiki refers to a "DAT box". This translated virtual addresses to physical. IIRC it was 8

Oh, the old days. I used a Model 67 at college. The first paragraph in Wiki refers to a "DAT box". This translated virtual addresses to physical. IIRC it was 8 entries, fully associative. The reason it was called a "box" is because it was huge, perhaps the size of a refrigerator. Yes, this single CPU function was about the size of a "rack" of today's computers (the dimensions aren't exactly comparable, the DAT box was wider and not as tall as a modern-day rack). The reason it had 8 entries was because that was the minimum number required by the instruction set. You could have an "execute" instruction which crossed two pages (2 byte alignment, 4 byte instruction). It could target something like a "move character" (MVC) instruction (a memory-to-memory move of up to 256 bytes) that also might be in two pages. The MVC source and target could each be across two pages. 2 pages execute instruction 2 pages move character instruction 2 pages source operand 2 pages destination operand - 8 entry TLB minimum size needed by the architecture There were a lot of TLB misses in those days. :-) Of course, we didn't call it a TLB at the time. Each bit of each of the 8 physical address registers went to a light bulb. When the insides of the DAT box were pulled out of the enclosure (this was possible while it was running) you could watch the lights blink. They did blink a lot, up until you hit a tight loop in FORTRAN. Then they'd freeze for a minute or more! That was one way to watch your program execute.