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[sindi keesan <keesan AT sdf.lonestar.org>]

> > So really the remaining culprits are:
> > 1) slow processor speed;
>
> Definitely.  Also the 16-bit architecture.  A 386sx
> is closer to a 286 than a 486.

Our 40MHz 386SX displays slowly.

My partner says a DX would access the video memory that is shadowed to RAM 
twice as fast.  32 instead of 16-bit access.


> > 2) absence of copro;
>
> Yes, X does use the copro for screen rendering.
> Copro emulation will be a significant burden on
> your already-overworked CPU.

We have a 387 coprocessor.  Still displays slowly.

> > 3) paltry video memory;
>
> I reckon your video card could be the biggest problem.
> Some old video cards are very slow.  Very, very slow.

We have a 386 board into which we put 4M RAM and tested two video cards 
with it.  First was 512K video RAM, slow board, and it displayed our test 
very slowly.  Then we put in our fastest ISA video card with 1MB RAM and 
it displayed just as slowly.  So it is not the video RAM or video speed.

The display was just a screen with 16 short colored stripes, nothing 
terribly taxing.

James, is this onboard video?  If not, do you want a 1MB video card?
It will at least give you higher resolution and more colors (not that 
linux will run any faster that way).

> 4) low network speed.
>
> Unlikely.  I've done lots of remote X via coax ethernet,
> and network speed was never an issue.

Serial network did not show any lag for us, with pentium and lots of RAM.

> > 3 is the only one I could really do anything about,
>
> Could be interesting, but we are probably flogging a
> dead horse.  If I had your 386sx, I'd rip out the
> motherboard and stick in one of my spare 486 boards.
> But even then most people would consider it very,
> very slow (but it would be a really fine Xterminal).

You could add more motherboard RAM but we can do that test here.
We are testing an SX33Mhz with 40MHz 386 coprocessor.  We have another
without coprocessor, and also a DX33 without coprocessor.

We would be happy to test these just for video speed but it is a lot of 
work to set them up with linux and networking and xterminal software.

A trident 8900 that tests out at 100K char/sec in a pentium board tests at 
9K/sec in the 386 SX33 with copro.  This is probably because of the slow 
RAM access to video RAM shadowed in motherboard RAM.

Testing the ATI VGA Wonder (512K video RAM) in the 33SX with 40MHz copro
gives us a Syschk video speed of: 10K  char/sec

(With other video cards that have free RAM slots we noticed that speed 
goes down as you add memory to the card).

Testing a trident 8900 (1MB video RAM)

1.  33SX with copro                       9.8K
    same without copro                    9.8K

These numbers vary from 9.8 to 10.0.  I will round to 10.
The coprocessor does not affect video speed.


386

1.  33SX  (16-bit) with or without copro                10K  ATI or Trident
2.  40DX without copro  - dead battery not working due to corroded trace

486  (32-bit)
3.  33 without copro (SX)  4MB RAM      9K ATI or Trident
4.  40 with copro (DX)  4MB RAM (4x1MB) 25K ATI
                        8MB RAM         24K ATI

The motherboard RAM appears to make no difference to video speed
under these non-stressful conditions anyway.

The 40MHz 486DX displays, on the same video card, about 3 times as fast as 
the 33MHz 486SX.  The DX won't work without the coprocessor (tho it is a 
separate chip) and we do not have a 33DX to experiment on so don't know if 
the faster video is due to the coprocessor (in the 486, but in the 386 it 
makes no difference) or to the faster motherboard speed (40 vs 33) or 
something else about the motherboard.  Both 486 motherboards have cache.
It might be possible to set some jumper to use the 486DX without copro.

I can't figure out quite why, but as Steven said, a 486DX seems to be much 
better than a 386 or a 486SX as far as video speed.

5.   Cyrix 586 133Mhz with 8MB RAM   50K                ATI card
(The Trident was about 100K on a faster pentium, but apparently all video 
cards benefit from the faster motherboard).

So the motherboard speed has a big effect on the video speed, same card.
386 or 486SX (33MHz) - 9-10K, 486DX (40MHz) - 24K, 586 (133MHz) - 50K.

I would not try to use a 386 as an Xterminal because of video speed, even 
with a fast video card, a copro, or 8MB RAM, tho the latter two might help 
with other things in linux.

We have left one laptop XT and two 286s (one with plasma screen) and three 
laptop 386s if anyone is curious about their video speeds, and a 
collection of ISA video cards (but we kept only those with 512K RAM or 
higher).

Sindi and partner Jim (who studied computer hardware in the 80s).


> Cheers,
> Steven
>
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keesan AT sdf.lonestar.org
SDF Public Access UNIX System - http://sdf.lonestar.org