Re: [Simh] pdp11 i/o addressing

...@gmail.com <mailto:mikestra...@gmail.com>, SIMH mailto:simh@trailing-edge.com>> Subject: Re: [Simh] pdp11 i/o addressing Message-ID: <mailto:cac20d2ngaew9cbkitu6sa14hsnsaa1ianhrckdt-q0oikbd...@mail.gmail.com>> Content-Type: text/plain; charset="utf-8" curmudg

Re: [Simh] pdp11 i/o addressing

And an even stronger curmudgeon warning here then. If people today claim that VM was designed to solve the problem of having more addressable memory, they are utterly confused, as VM don't give you any more addressable memory. Addressable memory is limited by the size of an address in the CPU,

Re: [Simh] pdp11 i/o addressing

> On Feb 16, 2018, at 5:01 PM, Rich Alderson > wrote: > >> From: Timothe Litt >> Date: Fri, 16 Feb 2018 16:15:28 -0500 > >> Overlays were used to compensate for limited virtual address space. > > ITYM "Overlays were used to compensate for limited address space." > > I first encountered the

Re: [Simh] pdp11 i/o addressing

> From: Timothe Litt > Date: Fri, 16 Feb 2018 16:15:28 -0500 > Overlays were used to compensate for limited virtual address space. ITYM "Overlays were used to compensate for limited address space." I first encountered the notion of overlays in IBM 1401 and System/360 programs. Neither computer

Re: [Simh] pdp11 i/o addressing

On Fri, Feb 16, 2018 at 4:35 PM, Larry Baker wrote: > In a true VM architecture, different objects can be distinguished by their > program addresses. This is a key distinction between memory mapping and > virtual memory > ​Larry - I 100-% agree with you. My point was that from a programmer's

Re: [Simh] pdp11 i/o addressing

9-5608 ba...@usgs.gov > Date: Fri, 16 Feb 2018 14:51:27 -0500 > From: Clem Cole mailto:cl...@ccc.com>> > To: Ethan Dicks mailto:ethan.di...@gmail.com>> > Cc: mikestra...@gmail.com <mailto:mikestra...@gmail.com>, SIMH > mailto:simh@trailing-ed

Re: [Simh] pdp11 i/o addressing

On 16-Feb-18 14:51, Clem Cole wrote: > curmudgeon warning below. > > On Fri, Feb 16, 2018 at 11:06 AM, Ethan Dicks > wrote: > > > I started on a VAX with 2MB of physical memory in a 16MB physical > address space but with 4GB virtual addresses.  Switching

Re: [Simh] pdp11 i/o addressing

On Fri, 16 Feb 2018 14:51:27 -0500 Clem Cole wrote: > curmudgeon warning below. > > On Fri, Feb 16, 2018 at 11:06 AM, Ethan Dicks > wrote: > > > > > I started on a VAX with 2MB of physical memory in a 16MB physical > > address space but with 4GB virtual addresses. Switching over to the >

Re: [Simh] pdp11 i/o addressing

curmudgeon warning below. On Fri, Feb 16, 2018 at 11:06 AM, Ethan Dicks wrote: > > I started on a VAX with 2MB of physical memory in a 16MB physical > address space but with 4GB virtual addresses. Switching over to the > PDP-11 was odd from that. > ​Sigh... I fear that is a fault of your e

Re: [Simh] pdp11 i/o addressing

On Fri, Feb 16, 2018 at 10:44 AM, Mike Stramba wrote: > Thanks Guys. > > I *had* downloaded a handbook... but it was the *oldest* one (1969) > ;), hence no mention of virtual memory in it ;) Yeah, Once you get to anything with an 18-bit Unibus, there's a distinction. What's sometimes hard to ge

Re: [Simh] pdp11 i/o addressing

Thanks Guys. I *had* downloaded a handbook... but it was the *oldest* one (1969) ;), hence no mention of virtual memory in it ;) Mike On 2/16/18, Clem Cole wrote: > +1 Paul's comments > > some resources - cut and pasted from a message to a young > engineer/mentee/student I have at the moment ;

Re: [Simh] pdp11 i/o addressing

+1 Paul's comments some resources - cut and pasted from a message to a young engineer/mentee/student I have at the moment ;-) PDP11 Processor Handbook 1979 AA-5075A-TC PDP-11 MACRO-11 Language Reference Manual (R

Re: [Simh] pdp11 i/o addressing

Mike, You should get yourself a good intro to the PDP-11, for example one of the PDP-11 Processor Handbook copies you can find on Bitsavers. It answers that question and many others. The key point is that you have to distinguish virtual addresses from physical ones. The I/O device addresses

[Simh] pdp11 i/o addressing

Greetings, I'm trying to figure out how console I/O works with the PD11. Or more generally I/O addressing E.g. A "sh TTO" gives : TTO, address=1564-1567, vector=64, 7p And 1564 (octal) is 4,194,164 dec, which is obviously out of range of the 64K addressable by any MOV instruction