Upgrading a Soldered CPU (AST Premium Exec 386SX/20)

[68k]

Howdy!

Well, boredom struck and I decided to get a little more SPEED out of my AST Premium Exec 386SX! The only problem: The CPU is soldered:



I carefully placed thermal tape and foil around the CPU to protect other components nearby, then used a heat gun to remove the CPU.

I cleaned the pads and applied flux, lined up the new CPU, and carefully soldered it in.

The original 40 MHz crystal (386 divides by 2) was replaced with a 50 MHz crystal for a new CPU speed of 25 MHz. I attempted 33 MHz but the system was not stable.

Stock NSSI reported ~3400 dhrystones

New speed is ~7400 dhrystones (with Cyrix utility installed)

Not bad for a few hours of work!

 

[paul.brett]

I want to report this post.....for being too awesome!

Replacing a soldered CPU? That is just mad!

Paul.

 

[NeXT]

I've seen it a couple times. I've also seen am5x86 chips swapped into later 486 machines.

 

[circuit]

That CPU has no business being in that laptop... and that's why it's so great!

 

[68k]

hahaha honestly thats one of the reasons I chose this laptop: It has 386SX/20 in the name!

AST also tucked the CPU crystal under a giant metal shield thats soldered in 6 places (the other system crystals dont have this, so its not for EMI). Performing this upgrade was directly defying a long-defunct company!