The "Good" Old Days - Complete Specs for DX-10 Operating System

http://www.bitsavers.org/pdf/ti/990/dx10/0946250-9701B_DX10_Vol1_ConceptsAndFacilities_Apr81.pdf
. . .
   DX-10 was writ mostly for the TI-990 mini-computers
   in the mid 70s. There are a few pix in the PDF and
   show people with clearly mid-70s styles.
   The 990 series, and DX-10, were an early multi-user/
   multi-tasking system aimed at the 'mini-computer'
   segment. Most users would have had plain terminals or
   graphics-capable serial terminals like from TexTronics.
   The 990 series used the TMS-9900 chip and near variants.
   This was an odd chip - kept the CPU registers out in
   ordinary RAM and could switch quickly between different
   sets of registers. At that time, the external RAM and
   CPU kinda ran at the same speed so little was lost
   putting the registers in RAM.
   I remember fooling with this chip on a TI-99/4a home
   computer (which, tragically, horribly under-used the
   neat new 16-bit CPU). There were ASM commands for
   dealing with the register, 'context', shifting. By
   that means many users with their own space could
   be implemented directly with the hardware.
   Anyway, the link is the full manual for DX-10 and
   also explains its symbiosis with the 990 hardware.
   How it is now AIN'T how it always was.