From: jwiegand@moe.eng.temple.edu (James Wiegand) Subject: Re: OS vs SYSTEM TYPE (long) [OS] Date: 14 Dec 1992 16:47:22 GMT
In article <BCR.92Dec13121930@hfl3sn02.cern.ch> bcr@cernapo.cern.ch (Bill Riemers) writes:
>
>After reading through all those back articles in both comp.os.linux
>and comp.os.bsd I've come to the conclusion the best thing for a
>new user to do would be to install MSDOS, LINUX, and 386BSD on thier
>computer. However, it sounds like you have to reboot your computer
>everytime you want to change your system type! This might seem
>reasonable until you stop and ask yourself what is the purpose of
>an OS? Mind you my understanding (mind you I am not a computer
>scientist) is that an OS is what provides an interphase between
>software and hardware for all programs. That is why on an APOLLO
>computer I can switch readily between the system types of
>BSD4.2, BSD4.3, SYS5.0, SYS5.3, and AEGIS without rebooting the
>machine. (Even without re-loging in.) All of these system types
>work through DOMAIN-OS.
[ ... ]
>The way this swapping of system type works on APOLLOs is:
>
> ver system-type command ==> excutes one command in the
> selected system type
>
> ver system-type ==> switches to the selected
> system type
>
>The system SYSTYPE tells the OS what type of system you are
>operating in. So rather than having a root '/bin' directory, you have:
>
> '/sys5.3/bin'
> '/bsd4.3/bin'
>
Here at Temple we have an Apollo ring (and I use that term loosely), so I
am somewhat familiar with what you are saying. One summer, they spent
a year upgrading to Domain 10.2 (the first Unix-y release they installed).
The problem is, the Apollo systems run Domain as their native operating
system (exec, file systems, ACL, window managers) and everything else
is layered on top. This brought programs like the print spooler,
IDEAS, and ANSYS to their knees. Print jobs whent from 10 min. to 40+ min.
The operating system doubled in size and swapped much more frequently.
This was on a network that already had space problems!
The point is, a system like this takes a 50% - 60% performance hit.
Having user-mode programs like the DOS-emulator is better since you
only take the performance hit when you need to. When you build it
into the kernel, there is NO way around it.
Besides, I don't think any of the gurus would write such a beast anyway.
jim
whose only affiliation with Temple is being one of their students.