You know, I have been racking my brains from time to time and I can't remember a thing about the ADP modifications to the 2020. So, the 2020 came with a maximum of 512K words, 2**9. An addition bit would have brought it up to a full megaword, 2**10, which is quite reasonable for the target audience (some kind of installation that didn't hold stock in the local power utility). I guess there may have been modifications to the 2020 build of the monitor to allow for the extra bit. I don't know if the Unibus devices could do DMA into the full address space. Did you pick up any software with these little jewels? The monitor changes might be interesting. > -------------------------------------------------------------------- > ---- On 4/24/20 12:12 AM, Dave McGuire wrote: > Nice! > > One of our 2020s is in the brown color scheme. You know what > that > means: ADP, and one more address bit. >> ------------------------------------------------------------------- >> ----- >> >> On 4/23/20 6:15 PM, Thomas DeBellis wrote: >> >> The solution for 4.1 was one of the finest hacks I have ever heard >> of; while the 2020 doesn't support extended addressing, it does >> support multiple address spaces, so what they did was move all the >> symbols into a separate address space. This was called 'hiding' >> symbols and I thought it was great because it made them harder to >> smash. However, all of that went out the window with 5.0, which >> fully supported extended addressing.