🚀 go-pugleaf

Last week I posted a message asking what was wrong with the '286. A 
number of people were kind enough to respond with some useful infor-
mation and opinions, and several asked that I post a summary. Well, 
here it is. I edited some of the responses to keep the length of the
summary reasonable. 

-Mark Newman
marknew@rosevax.rosemount.com

========================================================================

From Raymond Chen (raymond@math.berkeley.edu):
   There is no way to switch from protceted mode to real mode on a 286.
   The way it's done in practise is [1] save away the information you
   want to preserve, [2] set a flag to say "I am doing something goofy",
   [3] tell the keyboard chip to send a reset signal, [4] then halt the
   processor. Then when the reset signal comes (after a few milli-
   seconds), [5] the chip restarts in real mode, [6] notices the "I am
   doing something goofy" flag, [7] loads the context from the stuff
   you saved away in step [1] and continues.

   Gordon Letwin has called it "Stopping the car in order to change
   gears."
- - - 
From Dean William Wallwey (wallwey@snoopy.colorado.edu):
   You definitely want to get a 386SX. I have a 286, and I am very
   soon going to upgrade my mother board to a 386SX because 286's are
   going to be left behind. There are a lot of reasons to buy the 386SX.
   The 386 and 386SX both have very powerful memory mapping powers which
   are used by the new operating systems. They also both have what INTEL
   calls Virtual 86 mode so you can multitask DOS programs using Windows
   or DesqView for the 386. The small amount of money you save by buying
   a 286 machine will come back to haunt you tommorrow, even if you use
   it at home. The new software that is coming around the bend really
   needs large flat memory spaces (EVEN the NEW 386 version of OS/2
   later this year will take advantage of the 386's powers and really
   shine!)

   Some background info:
   The 386SX is identical to the 386 from a software point of view.
   The 386SX uses a 16 bit bus whereas the 386 uses a 32 bus so the
   386 is a little faster at the same speed because the 386SX has to
   reference memory twice for a 386's every one. Both the 386 and 386SX
   microprocessors are 32 bits internally and act exaxctly the same. The
   286 is a 16 bit bus and a 16 bit architecture. It does not have the
   powerful memory managment facilities of the 386. The 286 is *BRAIN
   DEAD* compared with 386 and 486 computers. The 386,386SX and 486 will
   run OS/2, mulitasking DOS, and UNIX, MUCH MUCH better than the 286
   ever will. Even the new Windowing word processors from MicroSoft
   (WORD for WINDOWS already out) and the future WordPerfect for OS/2
   will run so much better on a 386/386SX than the 286.

   Even if you don't think that you'll need the power of the 386 group,
   you will soon see even the simple "home" programs like word pro-
   cessing and spreadsheets longing for the 386/386SX. (I guess they
   already do with WORD for WINDOWS, and Lotus 1-2-3 ver 3.0 even though
   they will "run" on a 286).
- - -
From Michael D. Kersenbrock (michaelk@copper.WR.TEK.COM):
   The 286 is brain dead primarily because Intel made two major errors
   in it's design:
     1.) In protected mode (where it can access more than 1 Megabyte),
         the chip's MMU-ish architecture is "different" to the point
         that DOS can't handle it.  DOS MUST run in "real" mode (1Meg
         addressablity only).  When running DOS, protected mode IS
         entered sometimes, but interrupts have to be turned off during
         the time it is in protected mode.

     2.)  Given #1 above: when protected mode is entered, Intel provides
          NO way to go BACK to real mode. Because real mode is the mode
          that the chip powers up in, what an AT does to return into
          REAL mode is to have itself hardware-reset (by the keyboard
          controller I think) then, "recover" from where it left off. 
          Pretty wild.

   So, it's not brain dead in the sense of being useless, but brain dead
   in the sense that it isn't what it could/should have been had things
   been done just a little bit different.

   BTW - I just traded some stuff for a used 12-Mhz AT backplane, I hope
   to get it running this week (I've a Turbo-XT clone). Even with a
   brain dead processor, it should run two or three times faster than my
   old PC....

   BTW#2- Actually my old 10Mhz XT clone is adequate for home use (given
   also that it has 3Meg of EMS 4.0 memory that helps it a LOT).
- - -
From Marc Louis Levinson (gt0159a@prism.gatech.edu):
   The 286 is not really brain dead. The problem is that nobody has
   ever properly taken advantage of its capabilities. The chip has
   available what is called protected mode, which allows advanced
   memory handling and multitasking. Chances are slim that you can ever
   find a useful DOS application to use this mode.

   OS/2, UNIX and some Network software use 286 protected mode. The 386
   and 386sx can use advanced memory handling for normal DOS. Overall,
   the 386 series has faster throughput.

   If you are not planning to use hi power applications, like LOTUS 3,
   Windows [loaded to the max], Autocad and others to maximum perform-
   ance abilities, then a 286 is ok. Realize that much of the software
   now being developed will not run on a 286 but will run on an sx. Con-
   sider the lifetime of your computer before you buy one.
- - -
From Dick O'Connor (djo7613@blake.u.washington.edu): 
   There's nothing wrong with the '286. You should see the programs my
   wife and I did for the kids, for household organization, for
   gardening, for the church, on and on with an 8 MHz XT-compatible, and
   our new 286 machine screams thru all of them. No way we need a 386
   for home use, and few people at my office need them either.

   I can't speak for all of the mags, who have a vested interest in
   pleasing Intel, but I personally feel Bill Machrone and the editorial
   staff of PC Magazine are for the most part the most arrogant bunch of
   trend-setter-wanna-be's I've ever had the agony of reading. They care
   not for the actual uses of the individual, but only for unlimited
   desktop power. And those dudes use their machines for word pro-
   cessing!  What a laugh...

   Well, I shouldn't lump them all in the same boat. Machrone is
   arrogant, but Seymour is right about half the time, Dvorak *knows*
   he's trying to needle you, so I can take him, Manes is funny, and
   Zachmann has just guessed wrong in a BIG way about OS/2. Then again,
   they could all be the prophets of a new age, and I could be dead
   wrong!
- - -
From John Limpert (johnl@n3dmc.UU.NET):
   The 80286 cannot deal with numbers larger than 16 bits or data larger
   than 64K bytes without doing it in ugly, slow and error prone soft-
   software. The 80386 can work with 32 bit numbers and 4 gigabyte data
   areas (with the right operating system and software). Many programs
   were designed for 32 bit machine like the 80386 and if they will run
   at all on the 80286 (and many wont), they operate very slowly. Don't
   buy an 80286 machine, you will be wasting your money. In the future
   there will be a lot of software that will only be available for 80386
   class machines. 

   I am writing this on the 80286 UNIX system I bought several years
   ago. I wouldn't throw it out but I wouldn't buy another one today.