Internet Surfer 2.0/Internet Surfer 2.0 (Wayzata Technology) (1996).iso/pc/text/mac/faqs.415

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Frequently Asked Questions (FAQS);faqs.415



I. Introduction

The purpose of this posting is to give you the background information you need
to be a savvy buyer of 386/486 hardware for running UNIX.  It is aimed
especially at hackers and others with the technical skills and confidence to go
to the mail-order channel, but contains plenty of useful advice for people
buying store-front retail.  It was formerly part of 386-buyers-faq issues 1.0
through 4.0, and is still best read in conjunction with the pc-unix/software
FAQ descended from that posting.

This document is maintained and periodically updated as a service to the net by
Eric S.  Raymond <[e-mail]>, who began it for the very best
self-interested reason that he was in the market and didn't believe in plonking
down several grand without doing his homework first (no, I don't get paid for
this, though I have had a bunch of free software and hardware dumped on me as a
result of it!).  Corrections, updates, and all pertinent information are
welcomed at that address.  The editorial `we' reflects the generous
contributions of many savvy USENETters.

This posting is periodically broadcast to the USENET group comp.unix.sysv386
and to a list of vendor addresses.  If you are a vendor representative, please
check to make sure any information pertaining your company is current and
correct.  If it is not, please email me a correction ASAP.  If you are a
hardware-knowledgeable user, please send me any distillation of your
experience that you think might improve this posting.

II. Overview of the Market

The central fact about 386/486 clone hardware that conditions every aspect of
buying it is this: more than anywhere else in the industry, de-facto hardware
standards have created a commodity market with low entry barriers, lots of
competitive pressure, and volume high enough to amortize a *lot* of development
on the cheap.

The result is that this hardware gives you lots of bang-per-buck, and it's
getting both cheaper and better all the time.  Furthermore, margins are thin
enough that vendors have to be lean, hungry, and *very* responsive to the
market to survive.  You can take advantage of this, but it does mean that much
of the info in the rest of this document will be stale in three months and
completely obsolete in six.

One good general piece of advice is that you should avoid both the highest-end
new-technology systems (those not yet shipping in volume) and the very cheapest
systems put out by vendors competing primarily on price.  The problem with
the high end is that it usually carries a hefty "prestige" price premium, and
may be a bit less reliable on average because the technology hasn't been
through a lot of test/improve cycles.  The problem with the low end is that
price-cutters sometimes settle for marginal components.  UNIX is more
sensitive to hardware flakiness than DOS, so cut-price systems that might
deliver consistently for DOS lemmings can come around and bite you.  Use a
little care, and spend the $200-$300 to stay out of the basement.  It's worth
it.

The last point deserves a little amplification.  In the PC world, there's a lot
of "if it doesn't fail, it's OK".  It is common to ignore normal engineering
tolerances --- the allowances for variations in components, temperature,
voltage margins, and the like --- and to assume that anything which doesn't
fail outright must work.  Watch out!  For example, The ISA bus was originally
designed for 6 MHz.  IBM later updated that to 8 MHz, and that's as much of a
standard as there is, yet there are motherboards that will let you (try to!)
run it at 12 MHz --- 50% over spec.  Some cards are actually designed to work
at that speed with proper tolerances.  Others might work...or they might flake
out when they get warm.  Any systems vendor above the fly-by-night level is
going to shoot for a little more reliability than this, burning in systems and
(often) doing at least a token system test with some kind of UNIX (usually
XENIX).  Pay the few extra bucks it costs to deal with a more careful vendor.

Memory sufficiently fast and reliable for 486/50DX systems running UNIX seems
to be a particular problem (anything slower than 60ns will hurt performance).
The following war story by one comp.unix sysv386 regular is typical: "Dell 2.2
ran perfectly on 3 different AMI 486/50 EISA boards.  That is, after I replaced
faulty memory chips which caused repeated panics.  My conclusion, after
consulting with our hardware suppliers, was that current quality control on
top-end memory chips (NEC, Toshiba) is not good enough for 486/50's running
serious Unix.  The memory will pass every DOS-based test.  One has to plug and
play to get a set of simms that work reliably.  Part of the hazerds of leading
edge technology."

In mid-November, one correspondent recommended Goldstar Gold-on-Gold 1x3 or
1x9.  The idiots in Congress (a redundant phrase if ever there was one) have
imposed an "anti-dumping" (read: "protect American fat-cats") tariff that
immediately jacked up prices by $20 per megabyte.  Just in time for Xmas...

III. Buying the basics

In this section, we cover things to look out for that are more or less
independent of price-performance tradeoffs, part of your minimum system
for running UNIX.

A. Getting Down to Cases

Cases are just bent metal.  It doesn't much matter who makes those, as long as
they're above an easy minimum quality (on some *really* cheap ones, cards fail
to line up nicely with the slots, drive bays don't align with the access
cutouts, or the motherboard is ill-supported and can ground out against the
chassis).  If you're fussy about RFI (Radio-Frequency Interference), it's worth
finding out whether the plastic parts of the case have conductive coating on
the inside; that will cut down emissions significantly, but a few cheap cases
omit it.

Should you buy a desktop or tower case?  Our advice is go with tower unless
you're building a no-expansions personal system and expect to be using the
floppies a lot.  Many vendors charge nothing extra for a tower case and the
absolute *maximum* premium I've seen is $100.  What you get for that is less
desktop clutter, more and bigger bays for expansion, and often (perhaps most
importantly) a beefed-up power-supply and fan.  Putting the box and its fan
under a table is good for maybe 5db off the effective noise level, too.
Airflow is also an issue; if the peripheral bays are less cramped, you get
better cooling.  This is a good argument for a full tower rather than the `baby
tower' cases some vendors offer.  Be prepared to buy extension cables for your
keyboard and monitor, though; vendors almost never include enough flex.

For users with really heavy expoansibility requirements, rackmount PC cases do
exist (ask prospective vendors).  Typically a rackmount case will have pretty
much the same functionality as an ordinary PC case.  But, you can then buy
drive racks (complete with pwer supply), etc. to expand into.  Also, you can
buy passive backplanes with up to 20 or so slots. You can either put a CPU card
in one of the slots, or connect it to an ordinary motherboard through one of
the slots.

B. Power Supplies and Fans

Power supplies can matter but quality is cheap; give preference to those with a
Underwriter's Laboratories rating.  There's some controversy over optimum
wattage level; on the one hand, you want enough wattage for expansion.  On the
other, big supplies are noisier, and if you draw *too little* current for the
rating the delivered voltage can become unstable.  And the expected wattage
load from peripherals is droppong steadily.  The big old 300-watt supplies that
were designed for running several full-height 5.25" floppies are overkill in
these days of portable-driven lightweight 3.5" drives.  200 watts is good
enough these days, and the new breed of compact 200W supplies is quieter to
boot.

(About that annoying fan noise, ask if the fan on a target system has a
variable speed motor with thermostatic control --- this will cut down on noise
tremendously.  If not: I have seen a rave about, but haven't used, a
thermostatic fan controller called "The Silencer".  This tiny device mounts
inside your power supply and connects to the fan's power leads.  It
automatically varies the fan motor speed to hold a 79 to 82F temperature.
Write Quiet Technology, Inc. PO Box 8478, Port St. Lucie FL 34985.  Warning:
installing this may void your warranty!)

C. The Heart Of The Machine

Yet another basic decision, of course, is processor speed and type.  Until
recently, the hot sellers in this market were the 386/33DX and AMD 386/40DX,
which I'd say are reasonable minimum-speed engines for UNIX with X.  However,
recent pricing moves by Intel have moved the price of a 486SX25 below the
roughly equivalent 386DX33 chip.  The 386 is therefore effectively dead for new
hardware, and the 486SX/25 defined as the new low end (at least for the next
90 days or so).

At the system level, the current premium for 486 over 386 is about $150 as
many vendors move to phase out their 386 designs.  Unless you're buying a
portable, we definitely recommend going 486.

The 386SX machines were never a very good idea for UNIX; the 16-bit bus-to-CPU
path can choke your throughput.  The 486SX is even worse, a stupid marketing
crock with no technical justification whatsoever.  It's a 486DX with the
floating-point unit missing or even deliberately lobotomized out; the
difference *will* bite you in unobvious ways, for example if you use X which
does a lot of FP for graphics.  (One respondent opined that "SX" is
Intel-internal code for "sucks".)

A 486DX/33 has enough power make a good personal UNIX box.  For UNIX, this is
your floor; how far above them you want to buy depends on your budget and job
mix.  We'll have much more to say about this in the section on performance
tuning.

D. Motherboards and BIOSes

Provided you exercise a little prudence and stay out of the price basement,
motherboards and BIOS chips don't vary much in quality either.  There are only
six or so major brands of motherboard inside all those cases and they're pretty
much interchangable; brand premiums are low to nonexistent and cost is strictly
tied to maximum speed and bus type.  Unless you're buying from a "name" outfit
like Compaq, Dell, or AST that rolls its own motherboards and BIOSes, there are
only four major brands of BIOS chip (AMI, Phoenix, Mylex, Award) and not much
to choose between 'em but the look of the self-test screens.  One advantage
UNIX buyers have is that UNIXes are built not to rely on the BIOS code (because
it can't be used in protected mode without more pain than than it's worth).  If
your BIOS will boot properly, you're usually going to be OK.

If the above sounds too rosy, there is a catch; it describes *current*
hardware, not some of the historical botches.  And it's hard to know how old
what you're buying is.  You might actually be buying a motherboard that's been
sitting on the dealer's back shelf for a year, with a BIOS chip in it that was
in the drawer for another year before he ever stuck it in the board.  And some
of those older BIOSes and board designs are to be desperately avoided.  There
have been quite a few bogus cache designs that either don't work at all
(instant panic under UNIX) or that severely degrade performance.  A lot of
earlier designs have bus timing problems that show up in bad interactions with
host adapters and fancy graphics boards.  Bad memory designs were also not
uncommon.

A good, tricky way to keep the vendor from shipping you these fossils is to
specify a motherboard that can take 4MB SIMMs (as opposed to just the older 1MB
kind).  You want to do this anyhow for functional reasons.

There are a few other potential gotchas to beware of, especially in the cheaper
off-brand boards.  One is "shadow RAM", a trick some boards use for speeding up
DOS by copying the ROM contents into RAM at startup.  It should be possible to
disable this.  Also, on a caching motherboard, you need to be able to disable
caching in the memory areas used by expansion cards.  Some cheap motherboards
fail to pass bus-mastering tests and so are useless for use with a good SCSI
interface; on others, the bus gets flaky when its turbo (high-speed) mode is
on.  Fortunately, these problems aren't common.

Finally, one name-brand tip: *don't* buy DTK-brand motherboards for a UNIX
system!  They generate lots of spurious interrupts, which DOS is too stupid to
be bothered by but which completely tank UNIX.

You can avoid both dangerously fossilized hardware and these little gotchas by
sticking with a system or motherboard design that's been tested with UNIX (some
help with that below).

Some other good features to look for in a motherboard include:

* Gold-plated contacts in the expansion slots and RAM sockets.  Base-metal
  contacts tend to grow an oxidation layer which can cause intermittent
  connection faults that look like bad RAM chips or boards.  (This is why, if
  your hardware starts flaking out, one of the first things to do is jiggle
  or remove the boards and reseat them, and press down on the RAM chips
  to reseat them as well -- this may break up the oxidation layer.  If
  this doesn't work, rubbing what contacts you can reach with a soft
  eraser is a good fast way to remove the oxidation film. Beware, some
  hard erasers, including many pencil erasers, can strip off the plating, too!)

* Ability to go to 64MB on the motherboard (that is, without plug-in
  daughterboards).  Most EISA boards seem to have this (the popular Mylex
  MAE486 board is an exception).

* The board should be speed-rated as high as your processor, of course.
  It's good if it's rated higher, so upgrade to a faster processor is
  just a matter of dropping in the chip and a new crystal.

If your motherboard offers multiple cache sizes, make sure you know whether the
larger cache is required when using more than a certain amount of memory.  Or,
in general, fill the cache all the way -- cache-speed RAM is getting pretty
cheap.

Note, however, that hardware caches for system boards are really designed to
achieve effective 0 wait state status, rather than perform any significant
buffering of data.  As a general rule applicable to all clones, 64Kb cache
handles up to 16Mb memory.  256Kb cache handles up to 64Mb.  128Kb cache is
nearly redundant for a 16MB system; the benefit from additional caching is
statistically.  This means that running with 8Mb RAM, there is little
difference between a 64Kb, 128Kb, or 256Kb cache on the systemboard.

Finally, beware the infamous FP exception bug!  Some motherboards fail to
handle floating point exceptions correctly; instead of generating a SIGFPE they
lock up. The following fragment of C code will reproduce the problem:

    double d;

    d = 0.0;
    d = 1.0 / d;    /* floating divide by zero should yield SIGFPE */

John R. Levine <[e-mail]> explains: "The difficulty stems
from the fact that there are two ways to handle floating exceptions on a 486,
the right way and the PC way.  What the 486 wants to do is to generate an
interupt 16 when there is a floating point error, all entirely internal to the
CPU.  This has been the native way to handle floating point interrupts since
the 286/287.  The 286/287 and 386/387 each have a dedicated ERROR pin that the
FPU uses to tell the CPU that it's time for an error interrupt.

Unfortunately, the 8086/8087 handled interrupts differently.  The error pin on
the 8087 was wired to the 8259A interrupt controller, the same interrupt
controller that handled keyboard, disk, clock, etc.  interrupts.  The PC/AT
enshrined IRQ 13 as the one for floating interrupts.  (The details of this are
a little hazy to me, since the XT didn't have IRQ 13 tied to an 8259A, so the
AT must have at least changed the interrupt number.)  PC designs have generally
wired the 287 or 387 ERROR pin to the 8259A, not to the ERROR pin on the CPU,
or at best had some poorly documented way to switch between the two interrupt
methods.

In the interest of backward compatibility, the 486 has a mode bit that says not
to handle FP exceptions automatically, but rather to freeze the FPU and send a
signal on the FERR pin, which is usually tied to an 8259A which then feeds the
interrupt back as IRQ 13.  There is some extra complication involved here
because the FPU has to stay frozen until the interrupt is accepted so the CPU
can go back and look at the FPU's state.  Early 386/25 chips had a bug that
would sometimes freeze up on a floating point interrupt and you had to get a
kludge socket with a PAL that fixed the timing glitch that provoked the bug.

So as likely as not, the motherboard hardware that runs FERR out and back isn't
working correctly.  It's not surprising, few DOS users take floating point
seriously enough to notice whether the interrupts are working right."

When you specify a system, make clear to your vendor that the motherboard must
handle float exceptions properly.  Test your motherboard's handling of
divide-by-zero; if it doesn't work, press your vendor to replace it *and
send me email*!  Only by publishing a list of boards known bad can we
protect ourselves and pressure vendors to fix this problem.

The 386 UNIX Buyer's Guide posting (pc-unix/software) includes tables of
motherboards and systems known to run with various UNIX ports.

E. Peripherals

Peripherals are another matter, especially hard disks.  A good rule of thumb
for balanced configurations is that the hard disk should comprise about half
(or maybe a bit more) of the total system hardware price (exception: if you're
buying a really good monitor, like 16" or over, it's going to be expensive
enough to bust this rule).  Unless you're the exception who has to invoke
warranty due to a system arriving dead, most of what you buy from a dealer or
mail-order house is their ability to surf the Winchester market, make volume
buys, and burn in your disks before shipping.  We'll look at disk choices in
more detail later on.

These days, most vendors bundle a 14" monitor and super-VGA card with 1024x768
resolution in with their systems.  Details to watch are whether the card comes
loaded with 512K or 1MB of RAM (which will affect how much of that maximum
resolution and how many colors you actually get), whether the memory is
dual-ported VRAM (slightly more expensive but much faster), and whether the
monitor is interlaced or non-interlaced.  The latter is better and should no
longer cost extra; look for the abbreviation NI in the ad or quote and be
suspicious if you don't see it.

You should have a tape drive for backup.  Unfortunately, the tape drive market
is rather confusing.  Rather than try to give a capsule summary, we give it
its own section below.

We'll have much more to say about price/performance tradeoffs in peripherals
in the next major section, on performance tuning.

F. Keyboards

Hal Snyder of Mark Williams, Co. <[e-mail]> sent us the following caveat:

We find that about 10% of cheap no-name keyboards do not work in scan
code set 3.  We are interested in scan code set 3 because only there can
you reprogram the keyboard on a per-key basis as to whether keys are
make-only, make-break, or autorepeat.  It is a big win for international
support and for X.

Keytronic, Cherry, and Honeywell keyboards, as well as a large number of
imports, work fine.  My advice is to either by a respected brand of
keyboard, or deal with a vendor who will allow you to return an
inompatible keyboard without charge.

G. Power Protection

Finally, I strongly recommend that you buy a power conditioner to protect your
hardware.  MOV-filtered power bars make nice fuses (they're cheap to replace),
but they're not enough.  I've been delighted with my TrippLite 1200, which you
can get for $139 or so by mail order.  A fringe benefit of this little beauty
is that if you accidently pull your plug out of the wall you may find you
actually have time to re-connect it before the machine notices!

The tecbical info in the remainder of this section is edited from material
supplied by David E. Wexelblat <[e-mail]>.

There are several levels of power protection available to the home computer
user.  I break this down into 4 levels; others may have different ways of
classifying things.  The levels are:

    1. Surge Suppressor
    2. Line Conditioners
    3. Standby Power Supplies
    4. Uninterruptible Power Supplies

and here's what they mean:

1. Surge suppressors

These are basically a fancy fuse between the source and your hardware; they
clamp down spikes, but can't fill in a low voltage level or dropout.

This is a bare minimum level of protection that any piece of expensive
electronics should have.  Note that this applies to more than just AC power;
surge suppressors are available for (and should be used on) phone lines, and
RS-232 and parallel connections (for use on long lines; generally not needed if
the devices is colocated with the computer and all devices are protected from
outside sources).  Note also that *all* devices connected to your computer need
to be protected; if you put a surge suppressor on your computer but not your
printer, then a zap on the printer may take out the computer, too.

An important fact about surge suppressors is that *they need to be replaced if
they absorb a large surge*.  Besides fuses, most suppressors rely on on
components called Metal-Oxide Varistors (or MOVs) for spike suppression, which
degrade when they take a voltage hit.  The problem with cheap suppressors is
that they don't tell you when the MOV is cooked, so you can end up with no
spike protection and a false sense of security --- better ones have an
indicator.

You can buy surge suppressors at any Radio Shack; for better prices, go
mail-order through Computer Shopper or some similar magazine.  All of
these are low-cost devices ($10-50).

2. Line Conditioners

These devices filter noise out of AC lines.  Noise can degrade your power
supply and cause it to fail prematurely.  They also protect against short
voltage dropouts and include surge suppression.

My Tripp-Lite 1200 is typical of the better class of line conditioners --- a
box with a good big soft-iron transformer and a couple of moby capacitors in it
and *no* conductive path between the in and out sides.  With one of these, you
can laugh at brownouts and electrical storms.

Price vary widely, from $40-400, depending on the power rating and capabilities
of the device.  Mail-order from a reputable supply house is your best bet.
Line conditioners typically *don't* need to be replaced after a surge; check
to see if yours includes MOVs.

3. Standby power supplies (SPSs)

These devices are battery-based emergency power supplies that provide power for
your system via an inverter if the power fails. An SPS will generally have all
the capabilities of a line conditioner as well.

Note: these devices do not come on line until after the power fails, and have a
certain amount of delay of some of milliseconds before they come on line.  If
the capacitors in your power supply are not large enough, the SPS may not cut
in in time to prevent your computer from seeing the power failure.

Note also that many SPSs are marketed as Uninterruptable Power Supplies (see
below).  This is incorrect.  Any device with a non-zero cutover time cannot be
a true UPS.  If the ad mentions a cutover time, it's an SPS, and not a UPS.

The price range for these devices (depending largely on size and cutover time)
is $200-2000.  An SPS will *not* need to be replaced after absorbing a large
surge.

4. Uninterruptable power supplies (UPSs)

These devices provide full-time isolation from the incoming AC line through a
transformer of some sort.  These devices are on-line at all times, and if the
AC line fails, the batteries will cut in.  Your devices will see no
interruption of their incoming AC.  UPSs cost more, and provide more features.
They are the ultimate in power protection.  Many UPSs have an intelligent
interface that will notify a connected device of a power failure, allowing it
to shut down cleanly.  UPSs also provide the capabilities of a line
conditioner. The price range (for devices in the size range for a home
computer) are $400-$2500.  An UPS will *not* need to be replaced after
absorbing a large surge.

Now, given this information, how does one decide what to get?  For a system
that runs unattended, like most Unix systems, it is best to have a device that
provides both power holdover and a power failure signal.  Hence, for a Unix
system, a UPS is the best idea (an SPS is not the best power protection and
most have no intelligent interface).  At least one vendor sells
ordered-shutdown software for Unix, and it's fairly simple to write your own
daemon to monitor a serial port, and send init a SIGPWR signal when it sees a
certain signal.

Our recommendation for a home Unix environment is a configuration like the
following:

    a) A true on-line UPS for the computer system.  An intelligent
       interface is mandatory, along with appropriate software for
       ordered shutdown.
    b) Surge suppression on all phone lines, and also on serial/parallel
       lines that leave the room.
    c) Line conditioners on any devices not connected to the UPS.  If
       you do take a power hit, it's cheaper to replace a $50 line
       conditioner than a $1500 laser printer.

An important question is "How do I know how big a UPS to get?"  The watt rating
of the UPS should be at least the sum of the peak ratings off all equipment
connected to it.  UPS marketroids tend to quote you UPS capacities and formulas
like "sum of VA ratings + 20%" which (surprise!) push you towards costler
hardware.  Ignore them.  If a watt rating is not given, watts = 0.75*VAmax.

One other consideration is that you typically shouldn't put a laser printer on
a UPS --- toner heaters draw enough current to overload a UPS and cause a
shutdown within seconds.  The other thing is that you can't even put the laser
printer on the same circuit with a UPS --- the heater kicks on every 20-30
seconds, and most UPSs will see the current draw as a brownout.  So buy a
separate line conditioner for the laser printer.

Finally, read the UPS's installation manual carefully if you're going
to use it with other power-protection devices.  Some UPSs don't like having
surge suppressors between them and the equipment.

David personally recommends surge suppressors and line conditioners from
Tripp-Lite (available both mail-order and retail), and UPSs from Best Power
Technologies (Necedah, WI - 1-(800)-356-5737).  I can enthusiastically second
the TrippLite recommendation, but haven't dealt with Best Power at all.  There
are many other vendors for all of these devices.

Tripp-Lite has a whole range of products, from a $10 phone-line
surge-suppressor, to line conditioners and SPSs with prces in the hundreds of
dollars.  They have a line of $50-80 line conditioners that are good for most
peripherals (including your home stereo :->).

Best Power Technologies sells two lines of UPSs in the range for home systems.
The older and more expensive FERRUPS line (which is what David has) has a smart
interface, and very good filtering and surge-suppression capabilities.  He says
"I have a 1.15kVA FERRUPS for my home system, which is overkill with my current
hardware (although it rode out a 45 minute power failure with nary a whisper -
no reboot).  In 1990, I paid ~$1600 for this device, and that has since gone
up.  They also sell a newer line of Fortress UPSs.  These are better suited in
price for home systems.  I don't know much about them, as they were not
available when I bought my UPS.  I expect that this is what most people will
want to consider, though.  In addition, Best sells Check-UPS, a software
package (in source form) for monitoring the UPS and shutting it down.  I have
found Best to be a good company to deal with, with competent, knowledgable
sales people (who will be able to help you pick the right device), and helpful,
courteous, and responsive technical support."

Other things to know:

A UPS should be wired directly to (or plugged directly into) the AC supply
(i.e. a surge suppressor is neither required nor suggested between the wall and
the UPS).  In addition, a surge suppressor between the UPS and the equipment
connected to it is redundant and also unnecessary.

IV. Performance tuning

Here are the places where you can trade off spending against the performance
level you want to buy and your expected job mix.