NewLC - Memory - Have you ever wondered what kind of memory is present in your device? - Comments

Re: Memory - Have you ever wondered what kind of memory is prese

aml_1989 — Tue, 05 Feb 2008 17:32:48 +0100

Hi,

Thanks for the article, very good.

Can someone confirm for me where flash memory fits into all this?

I'm curious, as the N82 has 128MB of RAM and 100MB of Flash. Is this common to have more RAM than other types of memory?
Or was the N82 just a one off...
Or has wikipedia just got the specification table the wrong way round...

Thanks,
Andy.

Re: Memory - Have you ever wondered what kind of memory is prese

indrajit.tapadar@gmail.com — Fri, 26 Oct 2007 04:00:55 +0200

Thanks For the Comments

Re: Memory - Have you ever wondered what kind of memory is prese

Symbian_Neil — Thu, 25 Oct 2007 14:01:49 +0200

Very informative...Thanks

Re: Memory - what kind of memory is present in your device?

Isha — Mon, 22 Oct 2007 10:27:57 +0200

Thanks indrajit.tapada for such a nice and an erudite article . Thanks tote also to cover-up the remaining part . Your's job is appreciateable.

Thanks once again.

Regards
Isha

Re: Memory - Have you ever wondered what kind of memory is prese

indrajit.tapadar@gmail.com — Sat, 20 Oct 2007 15:05:44 +0200

Hi Tote,

I appreciate your reply and also giving some clarifications on some stuffs like 32MB RAM is not enough, I agree Nokia devices run out of memory on critical memory driving applications, and possibly engineers are thinking on those part as well.

Ya , I agree I missed out many things , coz the article was too bi by itself, and adding more things would have lost interest to the readers, I am happy that you have added many things what I missed out , and I once again thanks for the reply.

Cheers,
Indrajit

Re: Memory - Have you ever wondered what kind of memory is prese

tote — Sat, 20 Oct 2007 14:34:09 +0200

Thanks for putting the effort in writing such a lengthy and valuable article about memory-types. However, there are some thing that you did not mention or I "just" disagree with.

First of all, you wrote that ROM is the place where "stuff is stored". That's not the whole picture, I'm afraid. First, there are the memory cards where you can also store "stuff", of course, not all phones accept memory cards (for example, Nokia N91 did not allow that, but had a built-in hard-disk drive instead). Second, operators tend to pre-install some branded applications on C: drive (store stuff at other locations, than ROM), which is a flash-ROM. There is a common characteristic between memory cards and flash-ROM that they both preserve data even if device is switched off and they don't need extra power (by the battery) for that. Finally, you did not mention it, either, that there is a D: drive on Symbian devices, which is a RAM-drive. It's fast to read, but even faster to write. The interesting thing is that you can store files on that drive, I mean explicitly copy files from one location to the RAM-drive is allowed and efficient in terms of how long it takes. The files just simply do not remain there after power down.

Second, it's worth noting that Symbian has recently come out with demand paging support (in SOS 9.5), which means that whenever a program needs to load another binary it will not load the file entirely only that portion of the file that is really needed. For example, programs have loaded the whole DLL so far. Now it becomes possible to load only fraction of a DLL , on demand, and other portions only when they were really needed.

Finally, don't try to explain it to me that I don't need more RAM than 32 MB. You know, my Nokia N95 has 48 MB and it's not enough even for some simple purposes. For example, when I keep browsing multiple pages, then there is usually a certain point, when there is not enough memory for the Browser (it's the only application I launched) and it quits. I happen to know that there is a protection mechanism built into Symbian OS, called memory watchdog, that shuts applications down when OOM situation occurs (applying LRU approach). Nevertheless, Browser is not the only memory-hungry application. For example, I wanted to play with the built-in camera so that I took the sample program from Nokia that let me have insights of how camera API is meant to be used. I was shocked to see that that application "ate" 6(!) MB alone when it started. So you can imagine how much memory left for other purposes, for example, using the camera! So I think it's the right time to answer those questions, requests for more memory, which is one of the most frequently heard complaints about Nokia phones - that they lack memory.

Thanks for this article again!

Best,

Tote

Re: Memory - Have you ever wondered what kind of memory

rajesh.singh — Sat, 20 Oct 2007 05:14:40 +0200

Really a good article on Memory and is very appreciable too.
Thanks.
Rajesh

Re: Memory - Have you ever wondered what kind of memory is prese

indrajit.tapadar@gmail.com — Fri, 19 Oct 2007 16:19:35 +0200

Hai ,

Thanks a lot for clearing the concept of XIP ing in a nit more detail, and I appreciate it, It Corrected my knowledge of XIPing.I am sure readers will get a far better insight about memory..

Regards,

Re: Memory - Have you ever wondered what kind of memory is prese

twmd — Fri, 19 Oct 2007 15:28:42 +0200

Good summary.

A couple of things though

>> Note that this only works for programs. You can't XIP a picture or an audio file
That's not true. XIP is a bit misleading in that it refers to the fact that the NOR is in part of the CPU addressible memory (and so the Program Counter can reside in a NOR address).

If it's CPU addressable it means that the contents can be read like RAM and so doesn't need to be loaded.
This was used to good effect by Symbian by supporting the blitting of MBM bitmaps direct from NOR and also the reading .rsc resource strings direct from a ROM.

One disadvantage of XIP is that it's still much slower than SDRAM and so a beefy CPU can be crippled by slow execution speed - waiting on the NOR for each instruction. For this reason you end up shadowing a lot of CPU intensive code (e.g muiltimedia codecs) in RAM anyway.

>>XIPing also means faster application load times
Again, you have to study it - taking into account the slower XIP. Techniques such as demand paging help to speed up the loading of bloated applications by only loading the pages that are required and then keeping them around if the application is loaded twice in close succession.

Finally, the Samsung OneNand is interesting since it uses NAND internally, and supports XIP by exposing a NOR like address bus connector.
XIP performance is boosted by Internally caching NAND pages in an on chip RAM buffer.
I've not heard of anyone integrating OneNand onto a Symbian device, but it would be great to study the performance on a development board at least.

Memory - Have you ever wondered what kind of memory is present in your device?

indrajit.tapadar@gmail.com — Fri, 19 Oct 2007 14:33:01 +0200

Memory is used to hold stuff on your devices. Phone numbers, pictures, programs, music files, they all need memory to work. Ignoring old technology no one uses anymore and exotic technology that hasn't been released to the mass market yet, there are two types of memory: RAM and ROM. They're similar in that they both hold stuff. Their main differences involve speed and power.