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I had a Soekris net4511 that used to run m0n0wall and act as my router. Unfortunately, m0n0wall quickly outgrew the 32MB RAM that was soldered on to the main board.

A while later I got a net5501 to use as my router. Besides a faster processor, it has 512MB RAM. At some point, I started playing with the old 4511 again. While I could get OpenBSD booting and running with /var, /tmp, and /dev mounted to ramdisks, I only had about 2MB RAM left once everything was up and running. With some research and a little help from a friend, I successfully upgraded the RAM to 64MB. Here is how to do it.

DISCLAIMER: If you follow these steps and brick your Soekris box, don't blame me!

Getting the right parts

My 32MB board had a pair of Samsung K4S281632B-TC80 chips.

A picture of a 64MB board I found had a pair of K4S561632H-UC75 chips.

A google search for this part returned a lot of pages that were hard to read. I finally found a nicely organized page for a company called Memphis that looked credible, so I submitted a quote request for a couple of the chips. The reply stated that they were in Germany (I had assumed Tennessee!) and would not mail a couple chips half way around the world. It also mentioned that there were many different manufacturers that made compatible parts, and listed the Micron MT48LC16M16A2P-75 as one of them. With help from a friend of mine who works at DigiKey, I ended up placing an order for four MT48LC16M16A2P-7E:D TR chips (Digikey part 557-1060-1-ND).

The Operation

With the right eqipment, desoldering chips like this is easy. I don't have any desoldering equipment so I used the next best thing: a Dremel! Since these chips would not be reused, I didn't care how damaged they got during the removal process. Using a small cutting disk, I cut the pins right where they came out of the chips. I even cut into the chip a bit - as long I didn't damage the board or the traces.

Here are the old chips:

Chips removed - note the pins still soldered to the pads:

Here is what is left of the chips:

Pins desoldered and pads cleaned up with desoldering wick:

Here are the new chips:

One down, one to go:


Once both chips were soldered on, I powered it up and was pleasantly surprised to see it boot and count up all 64MB of RAM. Success on the first try! Looks like I have a couple extra chips now.

Oh, and in case you were wondering, powering it up with no RAM attached gives this message:
POST: 012345689bcefgh*-03-