[hga]

A question of $$$. See my above comment about the huge for the time memory size of the TX-2. Even the 7094 that CTSS was build on (inspiring later Multics and then UNIX(TM)) only had 2 banks of memory totaling that size, roughly half for the kernel and half for a single user program at a time.

You couldn't even begin to think about until, say, Intel started mass producing their groundbreaking first DRAM chip, which had a whopping 1024 bits of memory. And, hey, it was only 21 years until Apple shipped the first Macintosh ... with 128 KiB of DRAM and 64 KiB of ROM, 3/4ths of the TX-02's single memory bank....