Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!samsung!uunet!virtech!cpcahil From: cpcahil@virtech.uucp (Conor P. Cahill) Newsgroups: comp.unix.sysv386 Subject: Re: Is >16MB possible on ISA box (ISC 2.2.1)? Message-ID: <1991May13.115029.14295@virtech.uucp> Date: 13 May 91 11:50:29 GMT References: <1991May9.183908.9194@aai.com> <1991May11.131528.17370@virtech.uucp> <1991May13.004012.18572@pegasus.com> Organization: Virtual Technologies Inc. Lines: 39 richard@pegasus.com (Richard Foulk) writes: >Okay, so ISC blew it. It IS possible to run ISA bus Unix with greater >than 16 megs of memory. DMA is not a necessity. I've seen people >reporting 24 megs and more, in this forum, on ISA bus machines. I wouldn't say ISC blew it. The original System V 3.2 only supports up to 16 MB and requires changes to support additional memory. Somewhere along the way ISC decided that the market for >16MB on an ISA bus is too small to justify the additional effort required to support it. As far as I know, SCO is the only vendor to support > 16 MB (although I don't know if it will work on ISA bus systems, but I think it will). SCO did this by using the "epanded memory" trick that is used by many dos systems (it copies a page down below 16MB whenever a page is accessed by a bus operation). This works the same way under EISA systems, even though it isn't necessary there. On the other hand, ISC has committed to supporting > 16MB on many EISA systems in full native mode in release 2.3. (An update disk that works for several EISA MBs, but fails on some others is available. A more general one is in the works - no word on the actual release date). >So what is the real situation today? Which 386 ports of Unix will support >greater than 16 megs on the ISA bus? (Did the MEMRANGE spec actually >vaporize with ISC's 2.2, or is it just hiding somewhere else?) The MEMRANGE spec went away in 2.2, but I don't think it worked correctly in 2.0.2. We set up a system with 32MB of memory and a 12MB ram disk. When we went above 4MB of processes, the system crashed. One of my distributors told me that they did a similar test with no ram disk and the system crashed when they went above 16MB of processes/kernel. So while the system said it saw more than 16MB, it appears that it did not use it correctly. -- Conor P. Cahill (703)430-9247 Virtual Technologies, Inc. uunet!virtech!cpcahil 46030 Manekin Plaza, Suite 160 Sterling, VA 22170