Jerome -- it's "new math" :-) Seriously though, I guess I could have been a bit clearer in my description, but think I had mentioned somewhere along the way that the unit already had 4kw of memory, so I was trying to get to 28kw to leave IOPAGE open. I also just realized that the boards have a "page 7 disable" which operated like the S100 "phantom" signal which is why a 32kw board would work. Learning lots during this process. Everything I forgot about my 11/34a is starting to come back.
Sent from my iPhone > On Feb 10, 2016, at 3:05 PM, Jerome H. Fine <jhfined...@compsys.to> wrote: > > >Richard Cini wrote: > >> Jerome -- good point about the IOPAGE. Maybe I'll get an 8kw and 16kw board >> -- that gives me 28kw with the included 4kw. I have no specific software so >> I don't need to tinker with reducing IOPAGE. >> Rich >> >>>>> On Feb 9, 2016, at 10:47 PM, Jerome H. Fine <jhfined...@compsys.to> wrote: >>>> >>>> Thanks guys. This is really helpful. I was getting confused between the >>>> M8044 and M7944 boards. Max memory for the LSI-11 is 32kw, right? >>> Correct, the maximum memory on a board is 32kw. >>> >>> For an LSI-11 (aka PDP-11/03) without any MMU hardware, >>> the actual maximum memory that can be accessed must also allow >>> for the IOPAGE registers. Usually, the IOPAGE address range >>> is 4 kw which leaves 28kw for everything else, including RT-11 >>> (assuming that is what you are running). There is one option >>> available with some hardware to reduce the address range >>> set aside for the IOPAGE to just 2kw which then leaves >>> 30kw for everything else. Unless you are running a specific >>> program which requires the extra 2kw, it is probably not >>> worth the extra effort. > I hope that my version of arithmetic is for 8kw + 16kw = 24kw, > so somewhere I don't understand where the other 4kw comes > from. > > Then, since you are missing only 4kw out of the maximum of > 28kw (which is the normal maximum), you will not likely have > a problem unless you have really memory rich programs. > > RT-11 runs fairly well in just 16kw (or 32 KB), so it should not be a > problem. For my own work in which I need to run MACRO.SAV > as fast as possible, I run the program in 64 KB of extended memory > under a Mapped Monitor - which a PDP-11/03 (or an LSI-11) > can't do since there is no MMU chip. > > Of course, my actual CPU is a Pentium III which I use to run Ersatz-11 > so that RT-11 is running 15 times as fast as a PDP-11/93. And the > disk I/O is also a bit faster. I can copy a 32 MB RT-11 partition to > a second 32 MB RT-11 partition in under 2 seconds. Even with two > ESDI hard drives on a PDP-11/93, that takes over 4 minutes. > > Jerome Fine