Memory requirements for 386/ix (somewhat long)

[Liam R. E. Quin]

This article includes a lot of random thoughts on configuring 386/ix, and
some thoughts/experience on choosing a memory size.

My understanding is that the Honeywell-Bull (now Bull) 386 machine is
actually based on the Acer 1100 system.  This may not be true outside the
UK, and may not even be true there any more.
In the following, though, I'll assume that it is true.  You could find out
by looking at the motherboard, of course, but one of the reasons for
posting is so we find out [0.5 :-)].

> marwood at ncs.dnd.ca (Gordon Marwood) writes:
>> We will shortly be installing 386/ix for the first time (on a
>> Honeywell-Bull 386).  The recommended minimum memory is 2MB. 
For more than six users doing you will want at least 4 megabytes of RAM.
If they are not using GNU emacs, and are not using the C compiler, this
may suffice, particularly with an intelligent I/O board.
I have seen eight or so word-processor users on a 16 MHz 386 doing
just fine with 4MBytes of (32-bit-slot fast) RAM.

The disk and RAM speed is more important than the quantity on this sort
of machine.

>> All I can say about our
>> projected use is that it will be used for mail by a group of, perhaps 20
>> people, though I suspect no more than 6 at a time.
If that is all they are doing, a Digiboard or an Acer Smart board (I think
that this is what Bull use) will be fine.

>> We also expect to
>> use it as a file server for the same group, using NFS.  I suppose that
>> the closest comparison might be with someone who has used 386/ix on a
>> similar machine (20 MHz) for a similar group size.
If your purchasing dept. and/or budget is sufficiently flexible, you could
start with 2 Meg and expand later if you need to.
Check before you do that the system you buy has the larger chips, as
otherwise you may have to throw away your first 2 Meg in order to expand!
It is worth having a fully expanded motherboard, though, if you can afford it.

John G. De Armond (jgd at rsiatl.UUCP) writes:
> Don't even think of starting with less than 8 MB for a group that size.
> I've run 386/ix with 2, 4, and 8 meg and the transformation at each
> stage is awsom.  This machine is used for development by 2 people, news
> reading by a few more and handles a very heavy news redistribution load.
> With 2 people logged in and any kind of news processing going on in the
> background, the 4 MB machine paged rather badly.  When we upgraded to 
> 8 meg, the personality of the machine changed markedly.  Even when the
> system is not paging, it is much more responsive.

Of course, using a machine for development and for reading mail are
rather different.  For X-windows you *must* have 8 or more Megabytes of
RAM or you will quickly go insane go insane go insane go insa
Otherwise, less is fine.

> Note:  I have done no tuning on this system.  The kernal is configured 
> exactly as shipped and/or as kconfig builds it.  
It is *really* worth whil going through kconfig.
Configure the HPDD (this will make sense when you run kconfig -- select 7),
configure the system to use the default parameters for mamory size,
choose the facilities and drivers you want (as few as possible!), and
rebuild.  In particular, do not install any of the Xenix stuff from the
distribution floppies.
Configuring for memory parameters can double performance.  And if you are
using nfs, you may want to increase most of the STREAMS parameters, as
described in the System Administration Guide.

> With 20 users I presume you are connecting these in through an Ethernet?
> I hope so. 
S board such as Specialix (Acer 1100/20 only not 1100/25), Digiboard or
Corollary will be quite happy.  For 20 users I suggest Specialix or the
Corollary, and if you are using modems, avoid the boards (like the
Corollary 8x8, Chase and others) which don't give full 6- or (better)
8-wire modem flow control.
With host-based tcp/ip, NFS will keep the system busy, so either use the
Interlan board (check it is supported at the appropriate release) which I
have not had a chance to try yet, or the excelan board (excellent, but
their 386/ix suppor is poor).  It is better to use a serial card than
ethernet if you have host-based tcp/ip, becasue this reduces the number of
interrupts the CPU will get.

> 4 or 5 users on TTY logins is pushing it pretty far on this
> 20 mhz machine.
I disagree strongly with this!  (unless you use a dumb serial board)

> If you are installing Ethernet, you must use an intelligent
> card such as the Interlan unit supported by ISC.  I've used this card and
> can report that it performs very well.  In general, you want to avoid
> creating interrupts on the PC bus.  I've determined that it is almost 
> essential to have intelligence in anything that handles a datastream.
But I *do* agree with this (as already indicated)

> The configuration here is a no-name klone 20 mhz 386 with 8 mb of 80 ns
> RAM running 0 wait state.  The drive controller is an Adaptec 1272 SCSI
> adaptor with floppy interface (Recommended!).
The Adeptec SCSI card is well worth the extra over the Future Domain, if
you have the choice (based on limited knowledge, however).
I have used only the AHA1540S, not the 1272.
The fastest SCSI disks I have seen are the CDC Wrens, at 10.7ms...
And they are quite cheap, too.  Micropolis and Priam are other candidates,
to list but two...

> Video is a mono graphics
> board (slow).
This is relative.  The Acer board is actually one of the faster ones,
and some of them also emulate Hercules graphics (not the default board
shipped with the 1100/20, however).

> Serial interfaces consist of an 8 port intelligent card
> from StarGate (highly recommended) and a single PC-type async card with
> a 16550 uart (mandatory!)
If you only get five serial users, that would be a good reason *not* to
buy this card as far as I can see.... I wonder what I have misunderstood?

> Hard drive configuration is a high speed
> CDC Wren 40 meg drive for the root partition and 2 380 MB Newbury
> Data SCSI drives
Well, what do you know?  :-)
I suggest booting from the SCSI disk, however.  Also, don't buy disks from
Bull if you can help it!  They charge a fortune...

> a fast ST-506 AT controller.  Tape backup is a Wangtek 60 mb unit.  Slow
> but reliable.
The nicest tape drive I've used with 386/ix was the Archive Viper (SCSI).
Very, very fast, even with /bin/tar it moves continuously.
If you can't use  the Viper, the Wangtek is reasonably reliable, although
I did see some data suggsting Tandberg (Tandburg?) was better.
The wangtek goes quite fast with pdtar (or gnu tar if you are not a
commercal outfit or don't mind being infected with the Gnu Public License).
[sorry, couldn't resist a bit of politics :-) :-)]

If you can't get hold of ptar, use
	tar cvfb - usr (or wherever) | dd obs=500k of=/dev/tape
and it will go about 20 times faster (or it seems to...)
I couldn't get the Wangtek working with the Acer 1100/25, but I didn't
try for very long.  I imagine that Bull would use the Cypher drive, which
has a plastic slide that comes out of the drive about a centimetre, and a
handle one rotates in order to load the tape in place.
Again, this goes fastest with dd or pdtar.

> I HIGHLY recommend a separate drive for the root partition.  I spent
> many miserable days reinstalling from floppies after one disk problem
> or the other before I put a stone cold reliable root drive on the system.
> Unless you have at least 2 physical drives, almost any reconfiguration 
> of the file system mandates going back to floppies.

Actually it isn't too much of a drag to go back to floppies, as long as
* you make several (not just one) copies of the boot/install diskette, and
  try them out!!!
* you copy (with mount and cpio) the files from the boot diskette onto a
  directory on your hard disk, so that you can understand the INSTALL script.

> One further comment on the Stargate board.  This board and the company 
> behind it has been fantastic.  [...]
> initial test of the board consisted of setting up 8 simultaneous
> cats of a large file to each of the 8 ports at 38.4 kilobaud.  SAR 
> reported a CPU idle time of 98%!  I verified with a protocol analyzer
> that the pipe was being kept full on all ports.  In practical use,
> I can now force handshaking on all my Telebit feeds downstream even one
> using the Bell smart card.  I run zmodem transfers at 38.4 kb between 
> a PC and the system with no problems at all.  
So maybe the board *is* good, and you could have more than 5 logins?

> The installation went perfect.  Set a couple of dip switches on the board
> and tell the installation script these settings and let it rebuild
> a kernal.  I called tech support with a minor question (800 number)
> and was serviced by a very knowledgable person who helped me immediately.

In order to get the Acer 1100/25 to work reliably with the Adaptec board,
I found it necessary to adjust the bus timing dip switches to increase the
delay.  Then the systems passed saok testing with no problems.

With the serial board in place, you might have to disable the cache (from
CMOS setup), which turns out to have less effect than expected but is still
irritating.

If you have enough memory (say, 16 Meg), you could try experimenting with
a RAM disk.
Also, an 80387 makes a difference.  Note that (at least on the 1100/25) the
jumpers on the motherboard indicating presence or absence of a
floating-point chip are labelled incorrectly!  The labels are reversed.
Symptoms of getting them wrong include the /etc/dfspace at login time
either hanging or giving wildly incorrect results, SoftQuad's SQPS output
not printing on PostScript, Elan troff dumping core, and xeyes & xclock
behaving totally wrongly.
Since the operating system is compiled to use an 80387, a weitek will not
speed up the operating system or utilities -- only programs you write.
Hence, it is not worth the extra cost unless you are doing a lot of
development.

> BTW, after working with Stargate and their vendor-supported driver, I'm
> suddenly glad that Interactive is shoving driver support off to the 
> vendors.  Knowledgable service is refreshing.
Well, I have always found Interactive very helpful, but then I deal with
Interactive Ltd. in Britain.

Also, a couple of hints if you are not to be the only adminstrator:

* change the ends of /etc/rc0 and /etc/rc1 --
	echo "the system is down"
  must be changed to
	echo "please wait.  Do not switch off yet."

  because if you switch off between "the system is down" and "press any
  key to reboot", you will lose your hard disk.  All of it.  Bye bye.
  And if you have a cacheing disk controller, wait another minute.

  This is my only really major gripe with 386/ix.

* order the full documentation set, including the Prentice Hall manuals.
  You will need them, especially as 386/ix does not come with on-line
  man pages (although there is a reasonable "help").

* the default sendmail.cf is not very helpful.  You might want to replace
  sendmail with smail or something.  But hacking mailers is neither
  pleasant nor rewarding, and the only consolation is that is is less
  un-fun than hacking uucp.... and less fun but easier than hacking troff
  :-) :-)

I run elm under 386/ix with few problems.


Hope this helps a little.
These notes are all my own thoughts, not my employer's...

Feel free to mail/phone if you want.

Lee

--
Liam R. Quin   lee at sq.com  (a visitor, not an employee)
until Dec 20th. -- +1 416 963 8337 (visiting Canada)
After then -- +44 565 50021 (work, in Knutsford, UK, 10:00-19:00 GMT), or
+44 925 831084 (home; please, please no calls outside 07:30...01:00 GMT!!!)