Cisco 1841 Memory Upgrade

Note: this was written in 2012 and the technical details reflect that time.

As a contractor, you need to keep your skills up, so I kept a lab at home.  The clients I dealt with were mostly small and medium sized businesses. SMBs don't generally have large networks and I would often use the lab to try out ideas. 

I also liked to browse eBay for cheap gear. If you have looked at the Cisco 1841 router, you would see that many are advertised as having IOS 15, but beware; they often don't have enough memory to run. IOS12 will run on 128MB but IOS15 requires the full 384MB in order to run correctly.

This is what happens when you don't have enough memory:

This has happened to me twice now; twice I have purchased 1841's with IOS 15, and twice they have not had the required amount of memory to run IOS 15.

My first 1841 came with IOS12 and 15 so I just dropped back to 12. This is currently my home router. My latest purchase needs to run IOS15 for my lab work, so I decided to try a memory upgrade.

Memory prior to upgrade

This is the Cisco page showing how to add the additional memory. It is very straight forward requiring only the removal of one screw to get the box open.

Of course you can't just throw any old memory in there. The 1841 comes with either 128MB or 256MB of DRAM, with a single slot for upgrading to 384MB. In my case I have 128MB so I needed a 256MB ram module, and after a little research, This is the one to get.

Installation took maybe all of 5 minutes, and the router is up and running again:

Memory post upgrade

And that is all there is to it. I've been working with the router most of the day, and so far run into no issues with functionality or with the extra memory.

Programmable System on a Chip

In my time working for Ambar components, I had spent a lot of time working and training with the folks at Cypress Semiconductor, so when an FAE position opened up in Texas, they offered me the chance to apply which I did.  I was lucky enough to secure that position, and found myself relocating to the Dallas area. 

One of my first successes with Cypress semiconductor was the work I did with a digital sign maker in Texas.  The types of signs they designed and built are the roadside dot matrix signs. 

The PSoC module

Cypress had a product called PSoC ( Programmable System on a Chip). The PSoC was a small micro controller with configurable I/O which in this case was used for ultra bright LED driving and a serial interface for module to controller communication.  The module drove a small matrix of LEDs.  These modules would be connected together to form one large display panel.

The sign comprising PSoC modules

This is the back view of a completed display module.  The PSoC modules are connected via serial interfaces to a PC card, that handles the graphics and communications requirements of the sign.  The signs could be permanently mounted or portable mounted on a trailer (as seen below)

The completed Item

The completed item shown is one of the first trailer mounted signs.  

Laser Diode Tutorial

From 1998 to 2000 I worked as a sales guy for Fujitsu Quantum Devices.  The company manufactured lasers and receivers for telecommunications.  The position required an electronics engineer with sales experience to work with an applications engineer (who was a physicist) to sell to companies like Cisco, Marconi, Alcatel or anyone working with data communications backbone equipment.

Download the Laser Tutorial

Optical Networking Components