Re: Double interpretation overhead
There is a reason for the double interpretation. The TI-99/4 (and the later 4A, which has a better keyboard and a better graphics processor) was never intended to have a TMS9900 as its CPU. The intended CPU was going to be a custom made CPU that executed GPL as its native instruction set. The chip (it might have been the 9985, but my memory might be faulty) never made it, and after flirting with 8-bit CPUs such as the Z80, the 9900 was engineered in, on the grounds that TI would be damned if they would help Zilog by putting a Z80 in there, or Motorola etc.)
However, by the time this decision was made, the mother-board had been designed, and it was all 8 bit. Extra hardware had to be added (the 8/16 multiplexor) to do two fetches from memory and present it to the 9900 as a single 16-bit word.
It gets worse. Much worse. But no one would believe me, so I'll just leave it there!
Biting the hand that feeds IT
