On Sun, May 1, 2022 at 2:57 AM Chris Zach via cctalk <[email protected]> wrote:
> Looking through the manual I saw that this thing is nuts: It has a full > pdp11 in there (a T11 CPU) with something like 256kw of memory, 32k RAM > and the rest ROM chips. Which is impossible, however they built a bank > switching system into the terminal so the T11 could access more than > 32kw of memory. Yes, they literally built a MMU just so they could use a > pdp11. I find it rather annoying that with that much processor power there is no way to run a user program on the VT240. Maybe there is, but I can find nothing about doing that in the manuals. > > The 11 seems to control the basic functions and the graphics modes (4014 > and REGIS/VT220/VT125) through the graphics chip controller which looks > like the same one on the Rainbow's expansion video board. However there It's very like the Rainbow colour graphics board. There are a couple of programmed PALs in the memory update logic and I seem to remember that the ones in the VT240 and those in the 'bow are either identical or at least very similar. -tony
