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486 with cache problems

H

huubwen

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Joined
Jun 15, 2012
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45
Location
Netherlands, Europe
I bought a nice full EISA TMC PET48PN mainboard. The board has a 486DX-50 processor. The system is booting and running fine without problem or errors.
The performance is not what I expected it to be from a DX-50. It performed much worse than my 486SX-20. So I started the standard checks of the CPU and board.
The board has 256Kb L2 cache.

When verifying the cache it seems there is a problem with the internal L1 cache. It does not show up using CACHECHK V7. I checked the BIOS setting. Both L1 and L2 cache are enabled.

Is there something that I am missing here or is the internal cache simply broken?

Below the output of CACHECHK:



CACHECHK V7 11/23/98 Copyright (c) 1995-98 by Ray Van Tassle. (-h for help)
CMOS reports: conv_mem= 640K, ext_mem= 31,744K, Total RAM= 32,384K
486 Clocked at 49.9 MHz
Reading from memory.
MegaByte#: --------- Memory Access Block sizes (KB)-----
1 2 4 8 16 32 64 128 256 512 1024 2048 4096 <-- KB
0: 57 57 57 57 57 57 57 57 57 80 -- -- -- us/KB
1: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
2 <--- same as above.
3: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
4: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
5: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
6: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
7: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
8: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
9 10 11 12 <--- same as above.
13: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
14 15 <--- same as above.
16: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
17: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
18 19 <--- same as above.
20: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
21 22 <--- same as above.
23: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
24: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
25: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
26: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
27: 57 57 57 57 57 57 57 57 57 80 80 80 80 us/KB
28 <--- same as above.
29: 57 57 57 57 57 57 57 57 57 80 80 80 -- us/KB
30 <--- same as above.
31: 57 57 57 57 57 57 57 57 57 80 80 -- -- us/KB

Extra tests----
Wrt 37 37 38 37 37 37 37 37 37 37 38 38 38<-Writing
This machine seems to have one cache!? [reading]
!! cache is 256KB-- 19.3 MB/s 54.4 ns/byte (140%)
>>>> If you think you do have L2 cache, you might have FAKE CACHE chips! <<<<
10.3 clks
Hmmm. It looks like megabyte #1 isn't being cached!
Hmmm. It looks like megabyte #2 isn't being cached!
Hmmm. It looks like megabyte #3 isn't being cached!
Hmmm. It looks like megabyte #4 isn't being cached!
Hmmm. It looks like megabyte #5 isn't being cached!
Hmmm. It looks like megabyte #6 isn't being cached!
Hmmm. It looks like megabyte #7 isn't being cached!
Hmmm. It looks like megabyte #8 isn't being cached!
Hmmm. It looks like megabyte #9 isn't being cached!
Hmmm. It looks like megabyte #10 isn't being cached!
Hmmm. It looks like megabyte #11 isn't being cached!
Hmmm. It looks like megabyte #12 isn't being cached!
Hmmm. It looks like megabyte #13 isn't being cached!
Hmmm. It looks like megabyte #14 isn't being cached!
Hmmm. It looks like megabyte #15 isn't being cached!
Hmmm. It looks like megabyte #16 isn't being cached!
Hmmm. It looks like megabyte #17 isn't being cached!
Hmmm. It looks like megabyte #18 isn't being cached!
Hmmm. It looks like megabyte #19 isn't being cached!
Hmmm. It looks like megabyte #20 isn't being cached!
Hmmm. It looks like megabyte #21 isn't being cached!
Hmmm. It looks like megabyte #22 isn't being cached!
Hmmm. It looks like megabyte #23 isn't being cached!
Hmmm. It looks like megabyte #24 isn't being cached!
Hmmm. It looks like megabyte #25 isn't being cached!
Hmmm. It looks like megabyte #26 isn't being cached!
Hmmm. It looks like megabyte #27 isn't being cached!
Hmmm. It looks like megabyte #28 isn't being cached!
Hmmm. It looks like megabyte #29 isn't being cached!
Hmmm. It looks like megabyte #30 isn't being cached!
Hmmm. It looks like megabyte #31 isn't being cached!
Main memory speed -- 13.7 MB/s 76.6 ns/byte (100%) [reading] 14.6 clks
Effective RAM access time (read ) is 306ns (a RAM bank is 4 bytes wide).
Effective RAM access time (write) is 142ns (a RAM bank is 4 bytes wide).
486 Clocked at 49.9 MHz. Cache ENABLED.
Options: -t0
 
Well, you have nothing to loose :) - use a jumper to short the Turbo switch pins and give it another shot...
 
The system should work at full speed when the turbo switch is opened.
For start I'd make sure the jumper and BIOS settings are correct. CPU cache should be in write-through mode for the CPU (not write-back).
I'd also try some other DOS benchmark programs (like the Navratil DOS) to see how the system does there. If it performs less than it should, I'd try removing some of the main RAM (trying with 4-8MB only), in case the 32 are "too much" to be cached.
 
Well, case closed. Shorting the turbo jumper did the trick :blush:
Strange that the bios turbo startup setting is ignored. Cache performance is like it should be now.

The performance in games is still not what it need to be. I think that is has something to do with the Trident 8900C ISA card that I’m using. I would not like to use a VLB card in my 50Mhz FSB system. Perhaps I should start looking for a nice EISA VGA card :lol:

CACHECHK V7 11/23/98 Copyright (c) 1995-98 by Ray Van Tassle. (-h for help)
CMOS reports: conv_mem= 640K, ext_mem= 31,744K, Total RAM= 32,384K
486 Clocked at 49.9 MHz
Reading from memory.
MegaByte#: --------- Memory Access Block sizes (KB)-----
1 2 4 8 16 32 64 128 256 512 1024 2048 4096 <-- KB
0: 21 21 21 21 30 30 30 30 30 49 -- -- -- us/KB
1: 21 21 21 21 30 30 30 30 30 49 49 49 49 us/KB
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 <--- same as above.
19 20 21 22 23 24 25 26 27 28 29 30 31 <--- same as above.

Extra tests----
Wrt 37 37 37 37 38 37 37 37 37 37 37 37 37<-Writing
This machine seems to have both L1 and L2 cache. [reading]
L1 cache is 8KB-- 51.7 MB/s 20.3 ns/byte (229%) (142%) 3.9 clks
L2 cache is 256KB-- 36.4 MB/s 28.8 ns/byte (161%) (100%) 5.5 clks
Main memory speed -- 22.5 MB/s 46.7 ns/byte (100%) [reading] 8.9 clks
Effective RAM access time (read ) is 186ns (a RAM bank is 4 bytes wide).
Effective RAM access time (write) is 142ns (a RAM bank is 4 bytes wide).
486 Clocked at 49.9 MHz. Cache ENABLED.
Options: -t0


486dx-50 speedsys.jpg
 
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