Advent of Computing Episode 56 - TMS9900, an Alternate Future
May 16, 2021
Dive into the intriguing world of the TI TMS9900, the first 16-bit microprocessor, known for its unique architecture that supports multitasking. Explore Texas Instruments' fascinating journey from semiconductors to minicomputers, and imagine an alternate history where IBM embraced this chip instead of Intel. Discover its unusual register-in-memory design and the implications for time-sharing and multitasking. Finally, envision how a TI-powered personal computer might have transformed the landscape of home computing.
AI Snips
Chapters
Books
Transcript
Episode notes
TMS9900: First 16-Bit, Multitasking-Ready
- The TMS9900 was completed in 1976 and is the first 16-bit microprocessor on the market.
- Its architecture and lineage make it unusually well suited for multitasking compared to contemporaries.
Registers In Memory Enable Fast Context Switches
- TI's 990 series stored general-purpose registers in memory using a movable workspace pointer.
- This made context switches extremely cheap because switching workspaces changes the whole register set in one operation.
One-Instruction Context Switching
- Because registers live in RAM and the workspace pointer can be changed, a context switch can be done in a single instruction.
- This hardware feature makes the TI machines naturally inclined toward timesharing and multitasking workloads.
