Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!nrl-cmf!cmcl2!rocky8!cucard!ccnysci!alexis
From: alexis@ccnysci.UUCP (Alexis Rosen)
Newsgroups: comp.unix.aux
Subject: Some questions about A/UX
Message-ID: <941@ccnysci.UUCP>
Date: 21 Oct 88 19:24:24 GMT
Reply-To: alexis@ccnysci.UUCP (Alexis Rosen)
Lines: 71


I have a few questions about A/UX. I realize that there may be many sides to
some of these questions, but I'll take whatever I can get...
 
1) Can the Mac auto-reboot into A/UX automatically? If the machine dies,
   what happens? How often will it crash from high loads? What is a high
   load on a Mac IIx?
 
2) I know that the distribution comes with lots of source code. *What* source
   code? Can I get source for the stuff that's shipped only as binary?
 
3) Does A/UX have system accounting, and quotas, in the kernel, just like
   BSD? I know that "AU/X is all of SVR2 plus all of BSD 4.2 except ioctls",
   but what does that mean? Can it support the fast file system? What about
   stuff that comes with a standard BSD, but isn't part of the kernel? Am I
   even asking the right questions?
 
4) If the Mac crashes, the console will presumably go haywire. All diagnostic
   output will be lost. Can I make the console a serial device on one of the
   built-in serial ports? If not, can I stick a printer on one of those ports
   and redirect or copy ALL console output to the printer?
 
5) How many interrupts per second can the Mac deal with before getting
   hopelessly bogged down? The obvious answer is "it depends", but can
   someone out there give a rough approximation?
 
6) "Always balance your disk load." How much difference will there be between
   a system with one 620MB Wren and a system with a 620MB and a 90MB Wren?
   What is your favorite strategy with disks? Is it better to get a 90MB Wren
   or a 140MB Rodime as a second disk?
 
7) There is a well-known problem with Hayes-compatible modems on sysV machines.
   They often fail to reset properly after a session, so the next caller can't
   connect properly. I believe there is an answer, but I'm not sure. With A/UX,
   can I set up eight modems and be confident that they will work right? If
   Hayes-compatible modems are out, what do you recommend? The system would
   be used primarily for news and mail, so this is critically important to us.
 
8) To repeat an earlier query, is there ANYONE out there who runs more than
   three simultaneous users off of a Mac II or IIx? Any information about
   this would be deeply appreciated.
 
9) Lastly, I have asked in the past if anyone knew of a SCSI DMA board for
   the Mac II/IIx. Phil Ronzone was kind enough to spend a few moments with
   me explaining that DMA wouldn't be a big win. Nevertheless, all of my
   calculations indicate otherwise. What am I missing, if anything? Here are
   my numbers:

Assuming a Wren IV with 16ms access time, capable of transmitting data at a
sustained rate of 1 MByte/sec., and assuming the Mac II can do about 300 KB/sec
sustained, then a hard page fault (4KBytes) will take:

	  DMA: 16 ms + 4KB/(1MB/s)   =  16 ms +  ~4 ms = ~20 ms
 Mac w/no DMA: 16 ms + 4KB/(300KB/s) =  16 ms + ~13 ms = ~29 ms

So a page fault will take 50% more time without DMA.

   Of course, transferring larger amounts of data, DMA wins by a lot more.
   The more you transfer, the closer you will get to 330% speed for DMA. For
   loading a 500KB program, DMA would be 300% faster.

   Are there other factors I have overlooked? With a very fragmented drive,
   non-DMA loses a little less, but not a lot less. Anything else?

Thanks

----
Alexis Rosen                       alexis@dasys1.UUCP  or  alexis@ccnysci.UUCP
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