Newsgroup: it.comp.hardware
Titolo: Can I replace a 486DX33 Chip with a 486DX4/100 Chip

Hello
Can I replace a 486DX33 Chip in my computer with a 486DX4/100 Chip?  I have
heard it has something to do with the crystal speed in the computer.  If I
can can someone please tell me how to do it,  ie what type of 486DX4/100
chip(I have heard there are at least two versions) do I have to replace it
with,  or could you direct me to a web site with this info.
Also  how much realistically will it roughtly speed up my computer , 3
times???
Thank you
Antony

...
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I'm not a true expert here, but it sounds like it would depend upon your
motherboard.  Your bus is probably running at 33 MHz now, so you would
probably have to drop it down to 25 MHz with a CPU clock multiplier of 4
(4x25 = 100).  I don't think the DX4/100 supports a 33 MHz bus (if it did
you could do 3x33, which would be faster).  The motherboard may or may not
support the 4x clock multiplier.  If it does there would be jumpers on your
motherboard (or maybe settings in the bios setup).  Check your motherboard
manual.   As for performance, I think the Intel processor would have better
floating point performance than the AMD, if you care about that.   I'm not
sure if both are pin-compatible - that's a very important question.  The
speed increase would depend primarily on how much memory you have.  If you
have enough (i.e. it doesn't use the hard disk constantly), you'll probably
see a 3x improvement since the memory and peripherals will be running slower
at 25MHz.  If you don't have enough, it will be less of a help.
Jay

The cheapest solution is to use a 486DX2/66 because you dont need to 
know much or have a mobo that can do 3.3V. 
If you still want to forge ahead you need to identify
your motherboard type (VL-BUS/PCI/EISA/ISA), the voltage
jumper setting available, the cpu clock multipler settings
(CLKMUL), and the Motherboard clock(CLK)/bus timing settings.
many 486 motherboard may require jumper settings to adequately
recognize the CPU (AMD/Intel/Cyrix Model#) - an  incorrect jumper setting 
could cause the motherboard to hang up - if you dont have the
mobo manual this might be a problem. Knowing the mobo
manuafacturer and model number is helpful.
The Intel 486DX/4 runs at a clock multipler (CLKMUL) of 2x, 2.5X, or 3x
 with a bus speed of (CLK = 16Mhz, 20Mhz, 25Mhz, 33Mhz, or 40Mhz)   
An Intel 486DX/4 can also run at a clock multiplier of 2x when
  the bus speed is 50Mhz. Note that some memory cards will not
  run properly at 50Mz or may require additional timing delays
  to run properly.
Normally, The Cyrix and AMD 486DX/4-100 uses a clock multipler 
   of 3x  with a bus speed of 33 Mhz. 
VL-Bus motherboards and boards  max out at 40Mhz.
The Intel and AMD 486DX/4 requires a 3.3V (not 5V) setting and you must have
  a properly installed heatsink and CPU fan. You need physical
   clearance for this installation.
The cyrix runs on 3.45V (not 5v)!
if you dont have a 3.3v cpu mobo setting you can purchase
AMD486DX/133 with voltage regulator by PNY for 89.99
from Tiger Direct (P56-2200 PNY Quickchip 133). It
brings your system up the performance level of a
approximately P75. you can call Tiger Direct
at 
1-800-335-4055
Some people have Overclocked the 486DX4 and 5x86DX/133 
successfully to increase the performance even higher.
I have read that the 5x86DX/133 has been over clocked up
to 160 (clk=40,clkmul=4) which brings its performance
up to a P90. However, I have not heard about
the long term stablity this configuration.
Note that an upgrade to a  Super Socket 7 AT mobo, 32Mb 72 eDo ram, 
P266/AMD K2-300, and a  PCI/AGP 2Mb video adapter 
might be a have a better cost performance ratio
if you dont need strict 486 compatiablity.
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Designation: Socket 1
Number of Pins: 169
Pin Rows: 3
Voltage: 5 volts
Motherboard Class: 486
Supported Processors: 486SX, 486DX, 486DX2, 486DX4 OverDrive
Designation: Socket 2
Number of Pins: 238
Pin Rows: 4
Voltage: 5 volts
Motherboard Class: 486
Supported Processors: 486SX, 486DX, 486DX2, 486DX4 OverDrive, Pentium
OverDrive
Designation: Socket 3
Number of Pins: 237
Pin Rows: 4
Voltage: 5 volts / 3.3 volts
Motherboard Class: 486
Supported Processors: 486SX, 486DX, 486DX2, 486DX4, Pentium OverDrive, 5x86
Chcek of the pins will give you some idea of options....
regards
mrdata
=============== :^)
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