SD card as fast as RAM?

 

I the thread about defragging the memory on your GPS:

http://www.poi-factory.com/node/28965

the consensus is DON'T do it!

A number of people say they load their POI files onto an SD card and load them to their unit to save wear on the onboard memory. I've not used my SD card for anything but loading extra maps. (Personally I doubt that anyone would actually see a wear problem over the life of their units, but if it makes them happy...)

I'm just curious if this method allows access to your pois quickly or if you notice some lag as opposed to the onboard memory?

Access times always seems much slower when using an add-on card, both on my GPS and just about all the other devices I own, so for me I don't see how the wear saved is worth the extra read time.

Comments?

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Nuvi 2595LMT, Nuvi 1490T, Nuvi 260, GPSMAP 195

POI on SD Card

I have done both. Loading POI on to the GPSr itself and also left them on hte SD Card. I did not see any difference in the time taken to search, ocate and use them in either place. IMO it is a personal thing. If you can accept the MINOR inconvenience of the GPSr asking if you want to load the POI to the unit then you are good to go. If you cannot accept the MINOR inconvenience then load them to the unit.
I have yet to understand what the big deal is.

Just as fast

I have pictures and POI's loaded on a 4gb micro sd card and I it is just as fast as having them on the unit.

--
Bobby....Garmin 2450LM

POI on SD Card

After just coming from the defrag your SD card thread, maybe I can shed some light.

The discussion was loading your maps and POI files on an SD card will extend the life of the unit because the unit uses flash memory to store files, and flash memory has a limited life. If you exceed the life of your SD card it's cheap to replace. The GPS is not. With that said, the number or writes in the life of flash memory is 1-2 Million write cycles, almost nobody will "wear" one out.

This will not have any affect on the actual memory of your GPS which is probably DRAM not flash. and Flash is not as fast as DRAM. However for file storage, both your GPS and an SD card probably use Flash

I store the POI files directory on the SD card so that I always have them when I'm loading new ones, and don't want to lose the ones already loaded.

Beas

Kinda my point

billbeas wrote:

... the number or writes in the life of flash memory is 1-2 Million write cycles, almost nobody will "wear" one out.

...

I store the POI files directory on the SD card so that I always have them when I'm loading new ones, and don't want to lose the ones already loaded.

Beas

With that many cycles, it is highly unlikely anyone will wear out their unit's memory, the reason expressed, to "save the memory" seems almost as useless as defragging the memory. So the real reason to use the flash card is for backup or extra space.

I asked about access speed, but others say they don't notice any difference, and since I'm not worried about backup or space, using a card for anything other than loading additional maps, for me, offers no benefit.

Thanks

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Nuvi 2595LMT, Nuvi 1490T, Nuvi 260, GPSMAP 195

sd vs built in

i would think the speed of the SD card(100x,150x...) would make a difference as well.

Put POI's on both

I put my Custom POI's on the SD Card and the Alert POI's on the Nuvi. Then I can load them separately and do not have to do a Custom Load on the vast majority of my files.

--
NUVI 660, Late 2012 iMac, Macbook 2.1 Fall 2008, iPhone6 , Nuvi 3790, iPad2

POIs on SD Card

I keep my POIs on an SD card because it allows me to update the file without connecting the GPSr to the PC with a USB cable. My computer has a memory card slot. I insert the SD card directly in to the PC card reader slot, update the POI file, and then plug it right back into the GPSr. Up date done! I haven't tested the speed as compared to POIs on the GPSr, but it's plenty fast enough.

Dave MP
"If you can accept the MINOR inconvenience of the GPSr asking if you want to load the POI to the unit then you are good to go."

You only need to do this one time after each update. There was a discussion thread about this, but I haven't been able to locate it. Basically what you do is when you first power up the GPSr after inserting the updated SD card it will ask if you want to install the POI in the GPSr. Answer "Yes". On the next screen check the "Don't ask me again" box. Then click "Skip". The GPSr won't ask again until the next time you update the POI file on the SD card, but the POI is not loaded on the GPSr.

I don't "defrag" flash drives. It's a waste of time.

SDHC v internal flash

I use the SDHC for all my POIs and there is no difference in read speed to the eye. There is no need to ever defragment flash memory because it is stored contiguously (consecutive addresses). This is inherent of the write process architecture. The class of the card does make a difference in write speed performance, but read speeds are 10 to 20 times faster.

--
JRoz -- DriveSmart 55 & Traffic

.

I've never noticed a lag at all loading POI's. I have a plain old San Disk 1 gig SD card.

And yes, I do prefer the card over loading to the unit. grin

--
nüvi 3790T | nüvi 775T | Those who make peaceful revolution impossible, will make violent revolution inevitable ~ JFK

memory speeds, interface speeds...

Some SD (SDHC) cards are faster than others, but in these applications, that's probably not going to matter much.

What may matter more to you is the interface speed -- my 660 and 680 are (older) USB 1.1 devices. That means those map updates are going to take a while, pumping a gigabyte or so of data across a USB 1.1 link!

When I want to put lots of data on the SD card, I can connect the GPS to the computer, or I can pull the card from the GPS and plug it into the computer.

Going through the GPS sends things at USB 1.1 speeds. Pulling the card and plugging it into the computer does transfers at much faster USB 2 speeds.

Quite noticeable!

--
Nuvi 2460, 680, DATUM Tymserve 2100, Trimble Thunderbolt, Ham radio, Macintosh, Linux, Windows

Speed

I just lost 10 minutes of sleep reading this post. confused

--
Always on the Road Knowing where I've Been

SD card as fast as RAM?

rocknicehunter wrote:

SD card as fast as RAM?

No, SD memory is not as fast as RAM. However, the memory inside the GPS is also a solid state flash memory, so don't confuse it with RAM. The GPS certainly also has some RAM memory, and it is used for calculations, image buffers, and other important things, but in a comparison between the memory on an external SD or microSD card and internal flash memory, they are of a similar type and neither is RAM.

It is worth pointing out at this point that SD cards are available at many different speeds. Faster SD memory is sometimes marked class 2, class 4 or class 6, with the higher the number the faster the memory is. And I even have some expensive SanDisc extreme pro SD memory for my camera that puts class 6 memory to shame.

So how fast is external flash memory compared to internal memory? That is hard to say, I have not seen any published Garmin numbers on the speed of the internal flash memory. However, i expect that it is pretty fast and unless using Class 6 or better external cards, your internal memory is faster. And it may even be different for various Garmin models. Anyone want to publish time studies on transfers to and from internal gps flash memory contrasted to external memory on a SD card attached to the GPS?

I doubt that it matters very much if at all if you store your POIs on internal flash memory or an externl SD card. POIs are small and any speed penality from using an external card is likely to be low for simple POI use. However, even daily changes to a set of POIs is not likely to wear out the internal memory in your lifetime, so no GPS user should feel any need to buy an extra card, certainly not for POI use, unless they bought a very memory starved GPS.

I do see speed differences in my camera with a class 6 or an extreme class card. The camera is able to take successive photos when I hold down the shutter button much faster as compared to a generic slow SD card. This will also affect GPS users if they are transferring large quantities of data from an external card and if speed is important.

My suggestion is, if you are using the external card for mp3s, then you can likely use the least expensive card that you can find, your mp3s will play just fine. If you are using the external card for alternate maps (I have several topo maps stored on one of mine), the using a faster card will likely give you better performance, but it is not likely to be critical unless you are very impatient. If you are using the external card for POIs then I suggest there is really no reason to do this, but if it makes you happy go right ahead. Please just don't try to convince others that they need to buy an extra SD card too.

And don't be fooled that the more expensive SD cards of the same capacity are always faster. Occasionally you can find a class 6 or even a SanDisc extreme card for less than slower SD cards. Buyer beware.

One Time Option

Dave MP wrote:

If you can accept the MINOR inconvenience of the GPSr asking if you want to load the POI to the unit then you are good to go.

Not even minor if you choose to say, "Don't ask again" which is a check box option available when you answer the load question... at least it is every first time I've loaded something new on the Nuvi 765.

Edit: Sorry, I see this was answered prior to my response.

--
The Wizard of Ahhhhhhhs - Earned my Windmill 4/12/2010

Context Driven Travel

rocknicehunter wrote:
billbeas wrote:

... the number or writes in the life of flash memory is 1-2 Million write cycles, almost nobody will "wear" one out.

...

I store the POI files directory on the SD card so that I always have them when I'm loading new ones, and don't want to lose the ones already loaded.

Beas

With that many cycles, it is highly unlikely anyone will wear out their unit's memory, the reason expressed, to "save the memory" seems almost as useless as defragging the memory. So the real reason to use the flash card is for backup or extra space.

I asked about access speed, but others say they don't notice any difference, and since I'm not worried about backup or space, using a card for anything other than loading additional maps, for me, offers no benefit.

Thanks

I keep multiple SD cards with different sets of POI files on them.

One for Motorcycle Rides.
One for Traveling with the Wife.
One with for my never ending search for the perfect Hooters... um... restaurant. wink

--
The Wizard of Ahhhhhhhs - Earned my Windmill 4/12/2010

You Need the POI Factory Speed Reader Application

RAMTROL wrote:

I just lost 10 minutes of sleep reading this post. confused

wink

--
The Wizard of Ahhhhhhhs - Earned my Windmill 4/12/2010

I have maps, tourguides,

I have maps, tourguides, POI's and music on an SDHC card. I haven't noticed any slowdown in accessing data once the unit has booted. The boot does seem to be longer than I recall from before I had the card, but that's probably because it has to read a lot more in the boot phase. No biggie, I just hit the power button on the way out the door and by the time it's installed and I'm ready to go so is the Garmin.

speed

k6rtm wrote:

Some SD (SDHC) cards are faster than others, but in these applications, that's probably not going to matter much.

What may matter more to you is the interface speed -- my 660 and 680 are (older) USB 1.1 devices. That means those map updates are going to take a while, pumping a gigabyte or so of data across a USB 1.1 link!

When I want to put lots of data on the SD card, I can connect the GPS to the computer, or I can pull the card from the GPS and plug it into the computer.

Going through the GPS sends things at USB 1.1 speeds. Pulling the card and plugging it into the computer does transfers at much faster USB 2 speeds.

Quite noticeable!

In addition to the slower USB 1.1 speed, your data transfer is slowed down still more because the processor in the GPS has to handle the data. I would guess that the overhead would be 3 - 4 machine cycles per bit. That would add quite a bit to the transfer time.

congratulations on the windmill!

congratulations on the windmill!