I have used a Garmin GPSmap 60CSX for a number of years and I was very happy with the performance of the unit, I used it as a handheld unit for hiking and I also used it in a vehicle by connecting it to a laptop via the GPS USB port. On the laptop I used nRoute and Mobile PC as a navigation tool. I had developed a preference to using nRoute.

A few month ago while hiking the GPS started to act up. The unit would lockup and none of the buttons would operate.
The only way to restore operation was to pull the battery and restart the GPS. Everything appeared to operate normal again until the problem happened again.

I decide to buy a new GPSmap 60CSX and found they were no longer being manufactured but there was some in stock in the REI stores in the US and the bargain price of US$219.
So I had my daughter in the US buy one for me. I received it a few weeks later and did some comparisons between the old and new units. They should be the same, they are identical model number right?
I have found out a lot of interesting things because they are not totally the same unit. Here is what I found out:

I noticed initially that there were some software difference as follows:
new / old
Software ver. 4.20 / 4.00
GPS SW ver. 2.40m / 3.00s

You can get this info from your 60CSX by entering MENU>MENU>SETUP>SYSTEM>MENU. Choose "Software Version".
After doing some research on the internet I discovered that the new unit with the "m" in the GPS SW ver.utilizes a MediaTek chip while the old unit has a SiRF III chipset designated by the "s".
The SiRF III has a excellent reputation for sensitivity, fast satellite acquisition and ability to stay locked on even in heavy over growth.
Doing a Side by side test with the two units using identical mapsets on the microSD card I found the following:

The old unit appeared to start up much faster. That is on start up it took only a few seconds on the old unit to allow you to go from the start page to other pages in the GPS.
When I moved to the satellite page it appears the old chipset allows you to go map page and the satellite page even though a satellite lock had not been fully acquired yet.

On the new unit the GPS stayed on the start page a longer time than the old unit.The difference here was considerable 07 sec. for the old unit and 58 sec for the new unit.
It delay appeared related to the mapset size. As the mapset used got larger (2-3.5 GB) the GPS with the new chip took longer time to load the mapset than the old chip.

On a performance basis the old unit acquired satellites much faster than the new unit and the satellite signal strength on the satellite page was much stronger with the old unit.
This was done outdoors with the units side by side. If you Google it, others with more knowledge of the different chipsets than me state the SiRF III chip has a higher sensitivity than the MediaTek chip.
This basically translates into getting a satellite signal faster and keeping it under obstructed conditions.

The new Garmin 60CSX with new MediaTek chip also does NOT work with nRoute. This was confirmed with Garmin when I contacted them. They appeared very aware of it when I gave them the Software versions.
They state that the new software is not compatible with the old nRoute. They do not acknowledge they changed the chipset. That apparently is Proprietary Information.

Map transfers appear to work correctly. Other functions appear to be the same.
This could explain why the 4.20 Software version is not available for the GPSmap 60CSX on the Garmin website.
Version 4.20 is a software patch to get the units with the MediaTek chip out the door but one could easily conclude that the software/chipset upgrade broke the USB output if you needed to use it with nRoute.

The discussion with Garmin was lengthy, Initially they said they could do nothing about it and it was just a problem with old unsupported nRoute software. and new GPS software upgrades.
They had difficulty addressing the fact that the old 60CSX with the 4.00 software version worked without problem.
Garmin finally agreed in exchange to take my new 60CSX and give me a "like new" 60CSX with the 4.00 software version and the SiRF III chipset.

Related to this Garmin also offers an Exchange/Repair of the 60CSX. All Exchange/Repair units returned to the customer will be GPS SW ver. 2.40m MediaTek chip. A quote from Garmin "There will be no way in the future to get a device of that type unless you are able to buy from a store that somehow still has an old version."
My own tests later after my discussion with Garmin indicated that the new 60CSX appears to work with Mobile PC.

On a less important note the old GPS had the Americas Recreational Basemap V4 installed while the new unit had installed AMR Standard Autoroute Basemap NR 3.00.
The old basemap had considerably more detail than the new one. More roads and non business points of interest.
I recognize that this essentially gets overwritten by the installed maps but I, with my more detail is better attitude preferred the old basemap.
In an earlier discussion with Garmin they stated that I was stuck with the new less detailed basemap and it could not be changed even though the new Garmin Instruction Manual makes mention of the presence of the Americas Recreational Basemap.

This information may be useful to other GPSmap 60CSX owners who may be experiencing performance problems. It is not often you get to compare two versions of the same unit side by side.
Look after your 60CSX GPS with high performing the SiRF III chipset you may not be able to get another one.
If you research it on the internet you will find others who are less than happy with there repair exchange unit once it has been returned with the MediaTek chip.
I understand Garmin in their wisdom are using these new chips in the newer handheld GPSs so they are not getting any better.