SD Cards & TT3

Rappy · Occasional Visitor Joined: Dec 02, 2004 Posts: 9

I have been reading about the problems associated with SD cards and it appears to me that with rebranding etc it is impossible to know in advance exactly what you are purchasing .

While I am waiting for my Mio +TT3 +256Mb SD Card (brand unknown) to arrive I would like to ask a few questions.

1. I expect to be using TT3 + CheckPOInt + MemoryMap and will probably experiment with a few other pieces of third party software. Would a 512Mb SD card be of sufficient size? I don't know what the typical size of these add-ons are. I assume the SD Card is used for most of the storage.

2. Are there advantages to using two 512Mb cards if I required 1Gb of storage? Here I am thinking in terms of 'read' time. In other words comparing a 512Mb SD card and a 1Gb SD card with the same spec, would a 512Mb SD card be more efficient (faster) in terms of reading?

3. I have just come across this SD card:
Bytestor Hi-Speed SD Card 1GB
£64.99 with free p&p from Amazon.
Does anybody have any knowledge or experience of this brand name?
The spec states it has a Write Speed of 10MB/s (66X based on the CD-Rom Scale) but of course like other sd cards no Read Speed is specified.
Comments anyone?

Again, thanks in advance.

Ken

DavidW · Posted: Mon Dec 06, 2004 2:14 pm Post subject:

From some recent tests amongst the moderators and Team, it seems that the old rules on which SD cards to buy and which to avoid have changed somewhat. Hopefully we'll have something a bit more definitive to share soon.

You will probably find changing SD cards a pain - especially if you use your Pocket PC for more than just navigation applications. I have a whole wealth of stuff on my main SD card - including TomTom Navigator maps, POI files, ebooks, MP3 files (all ripped from CDs I own, I hasten to add) and Sprite Backup files. I never know where I am if I change SD card for another, so I prefer one large SD card that includes all my regular files.

I don't find performance changes that much between cards of the same design but different sizes - but you may find differences. There is a finite seek speed on memory cards - but I would guess changing from one bank of memory to any other bank is likely to take a similar amount of time. It's not like a hard disk where the further you seek, the slower it is. Details of the internals of memory cards are, unsurprisingly, proprietary information!

The spec of the card you mention sounds similar to a card I have recently tested that malfunctions. This card is an Integral "High Speed" 66x (10MB/s) 1GB SD card. The write speed is indeed high, but the card tends to shut down if you stress it too hard. TomTom Navigator 3 crashes randomly when you're driving, and I can make the card go wrong in my card reader connected to my workstation computer (Dell Precision 650, dual Xeon 2.66GHz with Hyperthreading on, Windows XP Professional, Belkin F5U248) if I start two large simultaneous read or write operations.

One thing to be aware of is that there are far fewer manufacturers of SD cards than there are brands. Some brands can change manufacturer from batch to batch.

David

Rappy · Occasional Visitor Joined: Dec 02, 2004 Posts: 9

David

Thanks for the comprehensive reply.

Ken

MarkHewitt · Posted: Tue Dec 07, 2004 4:33 pm Post subject:

Would you recommend CF over SD for storing maps? My CF GPS card has 512mb built in storage and I'm told by photographer friends that CF is faster than SD, so theoretically I should get better performance from CF?

But then there is also the issue that my GPS data is coming through the same interface!

DavidW · Posted: Wed Dec 08, 2004 12:16 am Post subject:

CompactFlash is usually faster than SecureDigital - and we don't see anything like the same number of issues reported with CompactFlash memory as SecureDigital memory. There again, I think there are far more people storing maps on SD than on CF these days.

I wouldn't worry about the extra load of the GPS data coming through the CompactFlash slot if you have one of those CF GPSes with built in memory. The GPS data doesn't amount to very much.

In the end, though, you can only experiment. If you find your system is unstable or slow, it's worth considering whether your memory card is to blame.

David

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