For a long time now, the SD card manufacturers have been increasing the card speed with "class" speed. The higher the number, the faster the speed that is transferred. AFAIK, the highest current speed is class 10. My SD card is a class 4 and it's fine for me. But as new nav program versions are created and introduced, I wonder if a higher class number isn't really required? If anyone REALLY knows, please make a comment. Thanks.

EDIT: I just had another thought [could be dangerous my thinking LOL]. What if a person would make a complete copy of their SD card to their computer first and then do a format of their SD card and then copy all the first copy back to their SD card? I wonder if that would also help with speed because there is no fragmentation on the newly formatted card.

I don't really know if in general there is a difference, all I can report is that using a class 10 SD card for Primo2 has made a difference for me. When I first started to use Primo2 after using Igo8 it seemed a bit clunky and certainly not as smooth as Igo8 was, this was resolved by using a faster SD card, now all runs smoothly and more often than not, a gps fix is already aquired by the time the program starts.

Thinks I may buy a 10 SD card, (I like speed )

I can tell you some details about SD if necessary but I keep it to the topic:
The main factor of interest in terms of speed is the writing speed as reading is always much faster.
Most GPS programs have to read a lot but actually only save files at exit, same for modifications.
All "random data" is processed in the flash memory so it does not affect interneal or SD.
Formatting is not recommended for a SD or USB unless you have errors or need to change the entire filesystem, a delete of all files and folders is sufficient.

There is no such thing as fragmentation on SD cards, at least not in the way known from a HDD.
It does not matter if a SD is in Fat, Fat32 or NTFS for example - only the SD controller reports the filesystem, internally it all stays the way the manufacturer intended it to be.

The loss of performance often comes from a slow device or things that are not really necessary like 3D buildings, overlays, many POI's on the map and so on.
Before you start thinking that your SD is too slow you might want to consider to install a naked version of GPS software and map, no extras, no skins, no gimmicks.
Since the internal memory is often quite fast an installion there with a map can give you a comparison.
One major factor that is often overlooked is the way the device reads and writes the data to SD - many devices only use a USB1.1 "connection" internally or have other speed limiting factors.
A read/write test in a card reader will show that :
Four test are required (only writing as reading should be faster anyway).
With a SD card reader
1. copy a huge file on the SD, for example a movie and note the time it takes.
2. copy many small files ( a few hundred) to the SD and note the time.
Test 1 checks the basic write speed, test 2 considers the SD controller speed as well.
3 and 4. Same as above but using the SD inside the device connected to the PC.

The only reason why anyone would need a Class higher than 4 is for video or digital cams as the speed has an effect on the number of pictures that could be taken in series and for video if the SD is fast enough for full HD including 5.1 sound or recording in 3D.
For normal use the SD Class should not matter at all as we mostly do reading - especially at the startup of a GPS program (here you might notice a slight difference if using a faster SD).

Downunder35m wrote:For normal use the SD Class should not matter at all as we mostly do reading

I concur. I have a Class 2 & numerous Class 4s. The 2 runs as fast as the 4s in a X20 unit. There is no lag at all.
Don't waste your money on anything higher than a 4.

Ok as you were chaps money not wasted, I think I understood most of Downunder35m post

hogan7777 wrote:Ok as you were chaps money not wasted, I think I understood most of Downunder35m post

As long as you & other members understand that a Class 2 is fine & anything over Class 4 is overkill, you are in good to go.

I have 512MB and smaller SD cards from years ago that I use for testing, there is no difference in speed between those and the newer SD cards in your average device.

On a slight tangent I use Primo 2 on a Chinese double din device. It came with a 2GN SD card which is umbranded and has no identification on it at all. I know that I am limited to 2GB because of the unit but I have now purchased two replacement 2gb cards and neither were compatible.

Anybode any idea what i should be getting. I could do with a backup in case this card fails.

archercj wrote:Anybode any idea what i should be getting

See if you can find an SD Card that does not have "SDHC" on it.
The "HC" is what may be making it incompatible with your device.