I think I have managed to get some of the answers to my own questions as to why
....SD memory cards work with some computers but not with others.....
The reference site that I have managed to find is:
The easiest question was what does the "class "writing on the SD card mean. There are three main MINIMUM transfer speeds to and from the card, respectively ;2, 4, 6, MB/s.
So if you buy a more expensive SD card, it could have, say, Class6
My other important question was ...why does it work with one computer and not another.?
Of course as I was transferring photos from a PC to a digital photo frame , really the my PC is the host.
Meaning the physical card reader slot and firmware is the business end.
In thethe index of the PDF quotyed above, we find
Figure 3-1: Hosts-Cards Usability .
The diagram is very clear. The old host reader writer can only read / write the older cards ( up to 2GB )
The new , well not very new as the spec is dated 2006, the new 4GB to 32 GB SD cards are now called SDHC, (HC = High Capacity).
The NEW host reader writer can on read / write the older SD cards ( up to 2GB ) as well as the SDHC cards ( up to 32GB).
So there we have it.
What do we have to do if we find our PC can't recognize an
Don't waste your time looking for a non existent firmware upgrade, when you can get readers/ writers for less than 12€ more or less.
That I think winds up this thread, which maybe could be a sticky is the moderators see fit..
I think this incompatibility situation could have been avoided by the SD card makers adding usability information , but then as always.... Caveat emptor ... or something like that.
written on the label