Are there any memory limits on older 386/486 motherboards with FreeBSD???

Are there any memory limits on older 386/486 motherboards with FreeBSD???

Post by User Rdkey » Sat, 19 Jul 1997 04:00:00



Except for my toy home box, I now have a fleet of fine FreeBSD boxes up in
my office.  Kudos to the FreeBSD folks.  I have run many lowendian flavors
of PC-ish *nix and must say that FreeBSD is the best of the lot in my hands.

Anyway, off to a particular fine point......

I have the chance to put 4 meg simms in my motherboards (486-33/66mhz boards).
That will give me 32 megs in each rather than the current 8 megs of 1 meg
simms in each.

My question is --- are there any 16mb or other such memory limits in the
current versions of FreeBSD?  I was not thinking that there was, but do
remember some versions of other *nices having problems at the 16mb barrier
on some motherboards.  My boards are GA-486VT Taiwan clone shop boards
that the books on them say will take 256K/1meg/4meg simms.  With 8 slots
and 4 meg simms that would give me a comfy 32mb of ram to work with.
I would not want to load up 32mb and only be able to use 16mb.

Any comments/pointers/suggestions appreciated.

Thanks

Bob Keys

 
 
 

Are there any memory limits on older 386/486 motherboards with FreeBSD???

Post by Matt Behre » Sat, 19 Jul 1997 04:00:00


: My question is --- are there any 16mb or other such memory limits in the
: current versions of FreeBSD?  I was not thinking that there was, but do
: remember some versions of other *nices having problems at the 16mb barrier
: on some motherboards.  My boards are GA-486VT Taiwan clone shop boards
: that the books on them say will take 256K/1meg/4meg simms.  With 8 slots
: and 4 meg simms that would give me a comfy 32mb of ram to work with.
: I would not want to load up 32mb and only be able to use 16mb.

You will be able to use all 32 provided your motherboard supports it.  I
run 20 in an old (pre-Windows 3.1) 486 board with no trouble.

--

  Zigg Computer Services                Visit http://www.cauce.org/
  http://www.iserv.net/~zigg/

 
 
 

Are there any memory limits on older 386/486 motherboards with FreeBSD???

Post by H. Ecke » Mon, 21 Jul 1997 04:00:00



Quote:> My question is --- are there any 16mb or other such memory limits in the
> current versions of FreeBSD?  I was not thinking that there was, but do
> remember some versions of other *nices having problems at the 16mb barrier

I seem to remember that ISA has a limitation for DMA memory transfers.
Simply ensure the BOUNCE_BUFFERS option in the kernel is set (which it
already is by default), that should do it.

Greetings,
                                Ripley
--
Ach komm, ich denke schon, da? die Raver sehr tolerant sind. Gerade bei dieser
Love Parade. Du mu?t dir nur mal ansehen, wer da sein wird: Westbam, Marusha,
Blmchen, ein Wagen vom Marienhof ... Also, das wrde meine Toleranzgrenze weit

 
 
 

Are there any memory limits on older 386/486 motherboards with FreeBSD???

Post by t.. » Thu, 31 Jul 1997 04:00:00




>> My question is --- are there any 16mb or other such memory limits in the
>> current versions of FreeBSD?  I was not thinking that there was, but do
>> remember some versions of other *nices having problems at the 16mb barrier

>I seem to remember that ISA has a limitation for DMA memory transfers.
>Simply ensure the BOUNCE_BUFFERS option in the kernel is set (which it
>already is by default), that should do it.

This is a hardware limitation that only comes into play if you have busmastering
or DMA ISA cards.  You can take a ISA-based machine, stuff it with 64MB of ram,
stick in a NE2000 net card, IDE disk controller, and Adaptec 1520 SCSI adapter
plus tapedrive, and turn off bounce buffers with no ill effects.  All these things
are PIO-mode only devices, no DMA or busmastering.

On the other hand, you can stick in a NE2100 card into the machine and even with
bounce buffers enabled crash it, because the lnc0 driver doesen't make use of
them even when they are defined, and in spite of the fact that the 2100 uses
DMA.

 
 
 

1. 386/486 Motherboard Schematics

I'm looking for schematics for 386/486.  we are running linux and it is
networked.  The problem is we have a severe size constraint and we must
make a smaller board.  The only thing is we don't want to get into a lot
of development time trying to come up with a new computer.  we just want
to rearrage an exisiting design that we know already works.  It can have
isa or pci.  Built-in sound/video or networking is o.k.  A built-in
network card would be awsome, but not a nessecity.  Thanks

Chris Burnside
Purdue University
Aeronautical and Astronautical Engineering

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