8->16MB slowdown: Do you have a 486 SX/DX-40 running Linux?

8->16MB slowdown: Do you have a 486 SX/DX-40 running Linux?

Post by Dave A » Thu, 22 Sep 1994 07:06:13



Hello,

I have a 486SX running at 40MHz with 16MB of 60ns RAM.  I've been
hearing about some people experiencing slowdowns when upgrading from
8->16MB, so I was wondering if I am experiencing the same problem
but just not know about it.  Since I have a 16MB SIMM, I can't
"downgrade" to 8MB and measure the performance difference.  I'm
getting about 20 bogomips(flops?) at startup.  Is anyone getting
significantly faster speeds with 8MB?  Or is there an easy way for
me to benchmark my computer?  xbench won't do any good, since I'm
using a Diamond Stealth 32 and tweaking it to get X to work.

Thanks,
Dave
--

#include <stdisclaimer.h>
 "When you were born you cried, and the world rejoiced.  Try to live your life
  so that when you die you will rejoice, and the world will cry."  -1/2 jj^2

 
 
 

8->16MB slowdown: Do you have a 486 SX/DX-40 running Linux?

Post by Matthew Aaron Armstro » Thu, 22 Sep 1994 15:38:06



Quote:(Leonard101) writes:


Quote:   writes:

     >> I have a 486SX running at 40MHz with 16MB of 60ns RAM.  I've
     been
   hearing about some people experiencing slowdowns when upgrading
   from 8->16MB, so I was wondering if I am experiencing the same
   problem but just not know about it.  Since I have a 16MB SIMM, I
   can't "downgrade" to 8MB and measure the performance difference. <<

      When you increased your RAM did you increase your cache also?

      I believe there is something mentioned in the FAQ about system
      speed deteriorating following an increase in system RAM without an
      increase in cache... sounds logical...

What you read probably referred to problems with some motherboards
not caching memory above 16 meg.  My move to 16 megs (from 8) didn't
change my BogoMip reading.  (It did speed up gcc compiles under X
while editing with emacs, however)

--
| Matt Armstrong              Successfully installing and using Linux at home


 
 
 

8->16MB slowdown: Do you have a 486 SX/DX-40 running Linux?

Post by Leonard1 » Thu, 22 Sep 1994 14:41:10


  >> I have a 486SX running at 40MHz with 16MB of 60ns RAM.  I've been
hearing about some people experiencing slowdowns when upgrading from
8->16MB, so I was wondering if I am experiencing the same problem
but just not know about it.  Since I have a 16MB SIMM, I can't
"downgrade" to 8MB and measure the performance difference. <<

Hi Dave,

   When you increased your RAM did you increase your cache also?

   I believe there is something mentioned in the FAQ about system speed
deteriorating following an increase in system RAM without an increase in
cache... sounds logical...

-Len

 
 
 

8->16MB slowdown: Do you have a 486 SX/DX-40 running Linux?

Post by nb.. » Tue, 27 Sep 1994 22:47:53


Dave,

 If you have an AMI BIOS, check to see if you have a field called "Cacheable RAM address
 Range".  If you do, make sure that it matches the amount of RAM in your system.


|>
|>   >> I have a 486SX running at 40MHz with 16MB of 60ns RAM.  I've been
|> hearing about some people experiencing slowdowns when upgrading from
|> 8->16MB, so I was wondering if I am experiencing the same problem
|> but just not know about it.  Since I have a 16MB SIMM, I can't
|> "downgrade" to 8MB and measure the performance difference. <<
|>
|> Hi Dave,
|>
|>    When you increased your RAM did you increase your cache also?
|>
|>    I believe there is something mentioned in the FAQ about system speed
|> deteriorating following an increase in system RAM without an increase in
|> cache... sounds logical...
|>
|> -Len

--

Nathan Bond                        Alcatel Network Systems

 
 
 

8->16MB slowdown: Do you have a 486 SX/DX-40 running Linux?

Post by Graham Worl » Wed, 28 Sep 1994 09:40:42


I think the problem lies with a speedup trick used on some boards. With 8 megs
you have filled two bank of memory up. Thus you can store alternate bytes in alternate locations. So to access consecutive bytes you half the access time, by
jumping between memory units. When you have 16megs you only fill 4 slots which
stops you using the speedup trick.

SOLUTION SPLASH OUT ON 32MEGS!!!


:    I have a 486SX running a 40MHz with 16MB of 60ns RAM.  I've been
:    hearing about some people experiencing slowdowns when upgrading from
:    8->16MB, so I was wondering if I am experiencing the same problem
:    but just not know about it.  Since I have a 16MB SIMM, I can't
:    "downgrade" to 8MB and measure the performance difference.  I'm
:    getting about 20 bogomips(flops?) at startup.  Is anyone getting
:    significantly faster speeds with 8MB?  Or is there an easy way for
:    me to benchmark my computer?  xbench won't do any good, since I'm
:    using a Diamond Stealth 32 and tweaking it to get X to work.

:    Thanks,
:    Dave
:    --

:    I found out that memory > 16MB was not being cached on my
: machine was when I noticed that a certain application program I was
: working on was taking significantly different amounts of time to
: execute every time I ran it.

:    This variability in execution times, it turned out, was caused by
: the fact that when the binary happened to be loaded into memory < 16MB
: the instructions it contained were being cached but when it happened
: to be loaded into memory > 16MB it was not being cached.

:    These variations in execution times were as large as a factor of 10
: in some instances.

:    When I recompiled the kernel with 16MB_LIMIT enabled, the variation
: disappeared with no increase in the average execution time that I was
: able to detect.

:    As soon as I get around to buying a second 128MB SRAM chip, I will
: take a look at what happens if I am running with 20MB ram, 256K cache,
: and 16MB_LIMIT disabled again.

:   Bill

:      
: --
: Bill Hogan



 
 
 

8->16MB slowdown: Do you have a 486 SX/DX-40 running Linux?

Post by Jamie Howe » Fri, 30 Sep 1994 15:43:09


: I think the problem lies with a speedup trick used on some boards. With 8 megs
: you have filled two bank of memory up. Thus you can store alternate bytes in alternate locations. So to access consecutive bytes you half the access time, by
: jumping between memory units. When you have 16megs you only fill 4 slots which
: stops you using the speedup trick.

: SOLUTION SPLASH OUT ON 32MEGS!!!

: :    but just not know about it.  Since I have a 16MB SIMM, I can't
: :    "downgrade" to 8MB and measure the performance difference.  I'm

he has 1 16meg simm. NOT 4 4meg simms :)

--
 //////////////////////////
 /      Jamie Howell      /

 //////////////////////////

 
 
 

8->16MB slowdown: Do you have a 486 SX/DX-40 running Linux?

Post by Jim Troc » Sat, 01 Oct 1994 23:02:23




>: I think the problem lies with a speedup trick used on some boards. With 8 megs
>: you have filled two bank of memory up. Thus you can store alternate bytes in alternate locations. So to access consecutive bytes you half the access time, by
>: jumping between memory units. When you have 16megs you only fill 4 slots which
>: stops you using the speedup trick.

>: SOLUTION SPLASH OUT ON 32MEGS!!!

>: :    but just not know about it.  Since I have a 16MB SIMM, I can't
>: :    "downgrade" to 8MB and measure the performance difference.  I'm

>he has 1 16meg simm. NOT 4 4meg simms :)

  It sounds to me like the memory subsystem doesn't have enough TAG ram
to be able to adequately handle 16mb of address space. Check the manual
to find out what types/speed of SRAM to add for TAG, and where to put it.

Jim Trocki

 
 
 

8->16MB slowdown: Do you have a 486 SX/DX-40 running Linux?

Post by Warwick Allis » Tue, 04 Oct 1994 12:44:38



>he has 1 16meg simm. NOT 4 4meg simms :)

When the vendor was building my system, they told me the newest version of
the BIOS on the board actually INSISTED on paired SIMMs.  I had ordered 16M,
and they didn't find this out until late in the construction so for a weekend
I only had 8M (2 x 4M).  I ran a few benchmarks.  After it had been upgraded
to 16M (2 x 8M), I ran the same benchmarks.  The result was a slight increase
in performance with 16M (as would be expected - not a major speed-up, since
the benchmarks were CPU-intense, not using great RAM or IO buffering).

--
Warwick
--

 /     * <-- Computer Science Department,  /      WIT SPACE TO LET
 \_.-._/     University of Queensland,    /
      v      Brisbane, Australia.        /

 
 
 

1. 8MB -> 16MB Big slowdown on 486/50 with AMI bios.

        I have a 486DX2/50 with a November 1992 AMI BIOS running Linux
1.1.45, and I just went from 8 1Meg chips, to 4 4Meg chips and when
I did this, my computer slowed by a factor of 4.  It was really
sad.  But when I went back to MS-DOG, it ran fine.  No slowdowns
under DOG.  Can somebody tell me what might be the problem?  
Is there an option in the kernel besides the CONFIG_MAX_16 that might
have an effect?  I set the CONFIG_MAX_16 to n.  Help?

Any and all help is appreciated..

Aaron


--
Aaron Michael Sims - P.O. Box 24565    | Hefnet Linux Group


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