Database Develop

512Mb RAM - Getting it out ?

I have a Flash application that requires ~130Mb of RAM and I want to run it on my Galaxy S
I've installed Froyo JPK with latest flash 10.1, but just before the end of startup procedure I always get the "exclamation circle" icon which is apparently the "out-of-memory" message in flash.
I have tried to free up the memory with task killers and memory boster, but can't get it above 175 Mb, which is obviously still not enough, since probably browser and other applications/services use it back before the flash application starts completely. Or might be also some limitation my browser in Galaxy S ? -> see EDIT below
On HTC Desire this same application works like a charm.
So I wonder...
Is there any way to get more free memory ? [EDIT: Yes, with "Chuck Norris mode" app killers, but i does not always help and it's lame]
Is there any way to get more than 311-322Mb RAM used for Applications ? [EDIT: Yes, when developpers will found out the way how to get less memory used for video codecs or even found the misterious 32Mb which are yet nowhere to be found]
Can we expect to this memory issue to be solved in future Froyo releases ? [probably only Samsung knows that, but for now it seems very unlikely]
EDIT: Found out that I get out-of-memory with every single application when it reaches 128Mb of RAM usage.
This is again specific to SGS. Looks like this is some internal max memory allocation size per application/VM
So here is another question:
Is there any way to increase this limit (might be android internal or dalvik VM related)?

no
no
no
sorry to say that...

flypubec said:
I have a Flash application that requires ~130Mb of RAM and I want to run it on my Galaxy S
I've installed Froyo JPK with latest flash 10.1, but just before the end of startup procedure I always get the "exclamation circle" icon which is apparently the "out-of-memory" message in flash.
I have tried to free up the memory with task killers and memory boster, but can't get it above 175 Mb, which is obviously still not enough, since probably browser and other applications/services use it back before the flash application starts completely. Or might be also some limitation my browser in Galaxy S ?
On HTC Desire this same application works like a charm.
So I wonder...
Is there any way to get more free memory ?
Is there any way to get more than 309Mb RAM used for Applications ?
Can we expect to this memory issue to be solved in future Froyo releases ?
Click to expand...
Click to collapse
If you need that amount of memory you should use a computer.
Its not the phone thats the probem here. its what you try to run.
//Damian

I would personally put up money to get the RAM issue resolved.
People keep saying that 324~ MB is enough. That's not the point though. The point is that Samsung advertised 512MB. Any reasonable person would assume that, like other phones containing 512MB of RAM, that the phone would have 400+MB available for general usage. 324 MB for such a power phone is dismal. I consider Samsung's claim to be a form of false advertising. Yes, technically the phone has 512MB of RAM, but not according to the reasonable expectations of a consumer. Almost half of the stated RAM isn't usable to the end user for applications. This is a problem with the phone from the standpoint of delivering the expected value to the consumer.

Dear XDA Developer Legends,
Do you think it is possible that you will be able to free up ram that is allocated to the ram disk?
Yours,
Concerned Customers

Hm, maybe its applicable for a lawsuit?

andars05 said:
I would personally put up money to get the RAM issue resolved.
People keep saying that 324~ MB is enough. That's not the point though. The point is that Samsung advertised 512MB. Any reasonable person would assume that, like other phones containing 512MB of RAM, that the phone would have 400+MB available for general usage. 324 MB for such a power phone is dismal. I consider Samsung's claim to be a form of false advertising. Yes, technically the phone has 512MB of RAM, but not according to the reasonable expectations of a consumer. Almost half of the stated RAM isn't usable to the end user for applications. This is a problem with the phone from the standpoint of delivering the expected value to the consumer.
Click to expand...
Click to collapse
the phone has 512MB and you can use all. But the system use some of it.
Its only user that cant read and understand how it work hat keep asking about it.
And this phone has more ram that most have. So yes it is enough of ram.
'If you try to runt 50+ all time you will and up with low memory.
But its the same on a computer. none complain about that.
Only that you can only see 3.5GB on windows and use that on a 32.bit system. Well now you can see 4GB and all people are happy.. but they still cant use it, but its looks good.
That the same with this phone.
If samsung did show 512MB and did show how much that was free, all people that complain would be happy. but it dont change a bit what thay can use.

yaocheng said:
no
no
no
sorry to say that...
Click to expand...
Click to collapse
That make no sense
there is no reason to get less memory with the i9000 when comparable devices like the nexus one running the same OS version has 100mb+ more free ram

DamianGto said:
the phone has 512MB and you can use all. But the system use some of it.
Its only user that cant read and understand how it work hat keep asking about it.
And this phone has more ram that most have. So yes it is enough of ram.
'If you try to runt 50+ all time you will and up with low memory.
But its the same on a computer. none complain about that.
Only that you can only see 3.5GB on windows and use that on a 32.bit system. Well now you can see 4GB and all people are happy.. but they still cant use it, but its looks good.
That the same with this phone.
If samsung did show 512MB and did show how much that was free, all people that complain would be happy. but it dont change a bit what thay can use.
Click to expand...
Click to collapse
This misses the point of my original statement. The Nexus One is advertised (along with many other phones) as having 512MB of RAM. The N1 has 380-400+MB available of RAM available for applications, as do many other phones containing 512MB of RAM.
Yes, the system does reserve some for certain system functions. Even after those functions have been reserved on other 512MB models, the vast majority is still available to the end user. This is not the case on the Galaxy S series. This is evident by the original posters comment regarding his application.
To address your Windows example: Windows 32 bit actually states that only a portion of the 4GB is available for use. I don't see in the advertisements where Samsung states "Contains 512MB -- 324MB available for actual usage"
I think most consumers, like myself, would assume that the amount of RAM advertised is directly correlated to the amount usable for applications.
Otherwise, what's the difference between a phone advertised as having 384MB and the Galaxy S? They both could have the same amount of RAM available.

andars05 said:
Windows 32 bit actually states that only a portion of the 4GB is available for use.
Click to expand...
Click to collapse
But its not the case here.
+1 for the rest.

This is what i get if I run top command from adb from a freshly booted phone:
←[H←[JMem: 296300K used, 15048K free, 0K shrd, 6968K buff, 134720K cached
CPU: 1.3% usr 2.3% sys 0.0% nic 96.2% idle 0.0% io 0.0% irq 0.0% sirq
Load average: 0.99 1.33 0.59 1/351 3109
Wonder what this "cached" means.
Can somebody pls run this on HTC desire ?

I don't think our phone has 512mb of RAM physically available to the system. I think the phone has 512mb of RAM in total but it looks like 128mb of it is graphics RAM or something. Meaning we only have 384mb available to the system. The maximum amount of RAM I can ever get free is about 175mb so I don't think that it's reasonable that the system is using about 337mb of RAM. My desktop linux system uses less RAM than that on boot.

Isn't the memory allocation for graphics dynamic?
how often does the graphics really need all that ram?
any why aren't other devices affected by this? (doesn't the GPU on nexus or milestone for example need memory allocated?)

sionyboy said:
Do you think it is possible that you will be able to free up ram that is allocated to the ram disk?
Click to expand...
Click to collapse
Please explain. Which ram disk do you mean?

Also, since it runs on linux, cant we assign some space from the internal sd (or external) to make a virtual ram disk that would be used as ram when needed? some king a paging file that we know on windows...
And if this is possible, can we assign it to video so graphism will be a little slower but app will become faster?
I think there is something we can do if we can change assignation of ram, apps, and video to make this phone way much powerful.
(just an idea...)

franklin01 said:
Also, since it runs on linux, cant we assign some space from the internal sd (or external) to make a virtual ram disk that would be used as ram when needed? some king a paging file that we know on windows...
And if this is possible, can we assign it to video so graphism will be a little slower but app will become faster?
I think there is something we can do if we can change assignation of ram, apps, and video to make this phone way much powerful.
(just an idea...)
Click to expand...
Click to collapse
There's always Compcache..that worked like a charm on the G1 and Magic.

http://forum.xda-developers.com/showthread.php?t=724960
As you can see, all other Android phones reserve some memory to the system... It's just the way it is.

the sgs kernel creates amemory blackhole, that is, it starts using memory after a certain memory address.
It does that because many things in the hardware are using fixed memory addresses to allocate their own memory which is not managed by the kernel itself and the kernel will never touch or see it.
what you call "system memory" is usually memory used and seen by the kernel, for the OS's functionality: various applications, services, daemons, kernel daemons, kernel memory itself (its not much) and some time some ramdisks.
Every phone also uses that of course, which amounts for like 80-130megs. They also often use small black holes of like a couple of megs, but that's so little that no one will notice.
The sgs makes a big blackhole. To me it's more of a design fault, but not much you can do about it I guess. It would need someone who's going to read the complete hardware sheets to bypass that, if at all possible, lol. Or samsung.
I bet they fixed the design issue in the galaxy tab and either the chip has separate dedicated memory either there's no blackhole.
Another theory why the blackhole is necessary is that there's a bug in the chip and it's messing up a portion of the memory, so this portion is left unused (blackhole'd - never seen by the kernel) for stability reasons.
i hope this gives some insight.
reference from the previously linked post:
- Galaxy S [2.1] RAM = 512 MiB | Linux = 325 MiB | Reserved = 187 MiB (with I9000XWJM2 firmware)
notice the huge black hole here (187 megs)

I used to have more than 300mb free after reboot with nexus one...

DamianGto said:
the phone has 512MB and you can use all. But the system use some of it.
Its only user that cant read and understand how it work hat keep asking about it.
Click to expand...
Click to collapse
No, *we* can't use it all , because we != system. The debate is not whether or not there is 512MB of physical memory; there could be , since Samsung advertises as having 512MB, but its not all user accessible memory. We don't know for what the system is utilizing that memory, I don't think its for loading some of the core system components; otherwise we should be left with more free RAM like other devices with 512MB of RAM (i.e Nexus One). Its more likely that 188MB is used by either the GPU and other hardware or as a Ram disk.
In contrast, other phones having 512MB of RAM don't use user allocated memory for system or hardware use (at least not the same way Samsung does). They are somehow handling it differently, maybe their GPU's and Other hardware software counterparts have dedicated memory. Whatever said, at the end of the day in the user's point of view, Galaxy S DOES NOT have 512MB of RAM as what we were all led to believe . That is pure deception !!
If they knew this was the case then they should have alerted this to the users. For-example a spec sheet for Samsung Fascinates says 512MB Flash/384MB RAM they should have advertised Galaxy S like that instead of lying through their teeth.

[Q] RAM

Can anybody explain to me something about how the RAM works? So the phone has 512 mb of RAM, and only 330 available (I guess the OS takes the rest to 330). From those 330, around 100 are always used by something hidden. What is that?
Also if I stop some of the running services, sometimes that memory remains used.
What does eat my memory over time? I mean after some hours following a reboot my memory slowly starts to become used.
In the Running services tab there is a list of cached services and if I close any of them it eats more memory. How does that work?
I know, these questions are annoying.

128mb for tegra. that's why you have only 300mb+ for available memory

But why if I stop some processes such as the music player the RAM doesn't clear?
And why if I stop something from the Cached Processes tab it eats my RAM? (I can't find out what those cached processes are actually)

as far as i understand the system keeps it in memory in case you open something again and then it doesnt have to load everything over. and if there isnt enough for new apps it clears some ram.
this is not windows and the ram is supposed to be full. if im wrong about that someone correct me...
Sent from my Optimus 2X using XDA App

Yes you're right but the way Android kills processes when needed can be optimized, as sometimes the system is slow to free ram. In fact there are threshold values for different situations, that say to the system to free ram.
So the solution is not a standard task killer, but an optimization of values that triggers memory clean up. It's done for example by scripts like the one I use, see in my signature.

[Q] is there any know way to remove 1gb ram limit?

I understand that if an app have a 1gb ram requirement there must be a reason behind it, but i just discovered that Microsoft Research's Face Swap needs 1gb too.
I have a Lumia 720 and i'm used to have face swap app even with my old win 7.8 phone, it looks like a stupid and non-sense limit.
I tried to download the .xap from web store but it's encrypted so i can't do much. Someone have already lost some time on this?

You would have to edit the WMAppManifest File inside the XAP to remove the Limit so unless you can decrypt it you can't remove the Setting. Best idea might be to contact the devlopers though. I don't believe they would set the Limit unless they have reason to do so. It definitely is not set by Default.

How can we see 1GB ram requirement on the application page? I have lumia 620 and I cant install it too.
http://www.windowsphone.com/en-us/store/app/face-swap/0f55f905-77d3-4e09-8f2a-d8a41c77a02b

SerhatSoylemez said:
How can we see 1GB ram requirement on the application page? I have lumia 620 and I cant install it too.
http://www.windowsphone.com/en-us/store/app/face-swap/0f55f905-77d3-4e09-8f2a-d8a41c77a02b
Click to expand...
Click to collapse
Information such as region restriction or memory requirements seems to be hidden from user. Your will be warned on install attempt with "can't buy app" error and description.

eyeofhell said:
Information such as region restriction or memory requirements seems to be hidden from user.
Click to expand...
Click to collapse
Interesting. I think it wont be hidden, thanks.

SerhatSoylemez said:
Interesting. I think it wont be hidden, thanks.
Click to expand...
Click to collapse
the only way i found to read the "1gb ram needed" error is open windows store application's link from a qr code and then tap on the error message on the phone.
looks like we totally need 1gb for this :\
thanks StevieBallz for the explanation.. i hope someday wp8 will just optimize ram management and remove this limit! I suppose is possible, iphone 3gs with 256mb of ram can run heavy games like real racing 2, why a 512mb ram phone can't run a face swap application?

512 MB devices offer up to 180 MB of Memory for App usage. 1 GB devices offer up to 380 MB of Memory for App usage. The rest of the Memory is reserved for the System, Background Tasks like playing Music, Voice over IP calls like Skype or Background Navigation.
Basically if the Devs put the effort in to get their App running with a Maximum of 180 MB it can run on 512 MB devices. If they Need more Memory than that they'll have to Limit the App to 1 GB devices. There is nothing Microsoft can do to Change that, given that it's down to the Apps Memory footprint. I can't imagine that an App can use > 180 MB on a 256 MB iPhone so it's most definitely down to the Developer to Change this.

This is an very interesting theme!
I think windows phone hast problems work with pictures and the memory limit.
Yesterday I have upload an app to store names Picture Ripper Project.
This is an mass picture downloader, that downloads pictures from Internet websites to phone.
The user can create his own lockscreen and tile images cycler.
In the first version of this app I have so many problems with the SYSTEM OUT OF MEMORY!
When the Engine downloads 15 Pictures with an size from 300 KB, the app has shut down.
I don't know why the Memory of this pictures expands over the Limit!
Now I have write down two new download engines. The Image Downloader and the Image Links Downloader.
I have create an way to download up 100 pictures at once and its working if the size of the pictures not so big.
I need some tester for this app. I only have an Lumia 920 and a Lumia 820 to testing it.
If your interest, send me an PN and get the App for free when it is online!
Thank you!

xtrose.
This happens because you keep the pictures in memory, and do not free/close/dispose the file streams after download. The actual size of an image in memory is bigger than its size on disk. There is no problem with the system. Just your app is doing it wrong.

The basic problem is that a JPEG compressed Image when being opened is decoded to a bitmap array that takes quite a lot more space given that it isn't compressed. 10 1280x720 images can easily take up up to 10 MB even when compressed and can get as big as 50 MB when uncompressed.
That aside your problem most certainly has to do with references to those images being retained in your App (as mentioned by Mcosmin), so the memory is not freed up. You can debug that using the Profiler included with the Windows Phone SDK. There are WebCasts and articles by Microsoft that explain the usage of the tools.

In the Downloadengines I am do it this way!
Downloading the images to an temp file, create an Thumbnail of it, delete the file and download the next!
It works fine.
With the Thumbnails i can open Folders with more then 200 Pictures!
The app is online at the marketplace now!
http://www.windowsphone.com/s?appid=1034eecd-381c-41dc-9386-86498d0ffd17

You can do this a lot faster by using memory streams instead of file streams for temp file to avoid the slower isolated storage.

I am try this in the next version!
Thanks all

Horrible Memory management. Please help.

I love my Windows Phone a lot. Everything about it is just great. Size of the screen, resolution, Music+Videos hub, Office etc etc.
But, there is an issue. A very serious one. Memory Management.
Recently, Nokia launched an exclusive N.O.A.V 3 FREE version for India for a limited time. I couldn't get it, in spite of being in India AND having a WP8. Why? Low Memory.
I wanted Asphalt 7, as it is really low priced (lower than Asphalt 5) but I can't get it. Why? Low Memory.
Tumblr is a great looking app. Lovely Live Tiles, but...BUT, at a cost. Memory.
I have deleted a lot many apps as I don't need them anymore or were just plain bad. But it has left a permanent mark on the OS. It has consumed space which a deleted app should release when deleted. But no. I still see the app name, with the memory consumed. So, those bytes are now rendered useless. Again, the same problem, Memory.
I would really appreciate any help to free those used bytes so that I can get on with my life and get better apps. I am now even scared to the extent I don't download apps I know I won't be using after a while.
What a gorgeous OS, what a great user friendly UI, how beautifully smooth and fast, but all comes down to one very basic and fundamental flaw. Memory.
And no, I am not hard-resetting my phone.

I thought asphalt 7 was available for 512mb devices...
http://www.wpcentral.com/asphalt-7-heat-updated-reduces-file-size

GH0ST DR0NE said:
I love my Windows Phone a lot. Everything about it is just great. Size of the screen, resolution, Music+Videos hub, Office etc etc.
But, there is an issue. A very serious one. Memory Management.
Recently, Nokia launched an exclusive N.O.A.V 3 FREE version for India for a limited time. I couldn't get it, in spite of being in India AND having a WP8. Why? Low Memory.
I wanted Asphalt 7, as it is really low priced (lower than Asphalt 5) but I can't get it. Why? Low Memory.
Tumblr is a great looking app. Lovely Live Tiles, but...BUT, at a cost. Memory.
I have deleted a lot many apps as I don't need them anymore or were just plain bad. But it has left a permanent mark on the OS. It has consumed space which a deleted app should release when deleted. But no. I still see the app name, with the memory consumed. So, those bytes are now rendered useless. Again, the same problem, Memory.
I would really appreciate any help to free those used bytes so that I can get on with my life and get better apps. I am now even scared to the extent I don't download apps I know I won't be using after a while.
What a gorgeous OS, what a great user friendly UI, how beautifully smooth and fast, but all comes down to one very basic and fundamental flaw. Memory.
And no, I am not hard-resetting my phone.
Click to expand...
Click to collapse
If you're referring to the low RAM of your phone, you may try this,
Thanks,

I... *think* he means storage (not RAM).
I don't know what he means about "It has consumed space which a deleted app should release when deleted. But no. I still see the app name, with the memory consumed"; that part makes no sense. Deleted apps are removed and consume no storage on the phone. It's not even like "normal" Windows where installed programs occasionally don't clean up after themselves; the app manager on WP takes care of all installation and removal, and there's nothing left after it does so.

GoodDayToDie said:
I... *think* he means storage (not RAM).
I don't know what he means about "It has consumed space which a deleted app should release when deleted. But no. I still see the app name, with the memory consumed"; that part makes no sense. Deleted apps are removed and consume no storage on the phone. It's not even like "normal" Windows where installed programs occasionally don't clean up after themselves; the app manager on WP takes care of all installation and removal, and there's nothing left after it does so.
Click to expand...
Click to collapse
I was referring to memory and NOT RAM. And sorry, my bad, when I uninstalled the Bloomberg App, I still saw it in the Storage Check app consuming memory. But it isn't there today. I removed the Flikr Wallpaper app and it was gone in no time from the Storage Check app.
But, why isn't my Free Space increasing? It still says 1.5 GB free in spite of many apps removed. Also, there is a very mysterious 'Other' category eating up about 978 MB. And even Temp Files dont go all the way down to zero. If I say 'clear' to Temp Files when it is 500MB, after clearing its 388 MB.
I need to empty some space man.

GH0ST DR0NE said:
I was referring to memory and NOT RAM. And sorry, my bad, when I uninstalled the Bloomberg App, I still saw it in the Storage Check app consuming memory. But it isn't there today. I removed the Flikr Wallpaper app and it was gone in no time from the Storage Check app.
But, why isn't my Free Space increasing? It still says 1.5 GB free in spite of many apps removed. Also, there is a very mysterious 'Other' category eating up about 978 MB. And even Temp Files dont go all the way down to zero. If I say 'clear' to Temp Files when it is 500MB, after clearing its 388 MB.
I need to empty some space man.
Click to expand...
Click to collapse
Have you tried Shrink Storage App, and try to delete the search history.
Addition: IMO, if you are installing a large app and was interrupted and never continued the installation, the portion you initially downloaded remain on your phone. Its hard to remove that file.
FYI, that Other on storage is a windows bug.
Thank you,

"RAM" is Random Access Memory, and is commonly just called memory. If you want to refer to persistent storage, you should generally use another term. NAND (for NAND Flash, the type of storage used in phones), Flash, SSD, HDD (technically inaccurate for a phone but not confusing), or simply "storage" are all good options for what you apparently meant.
Most apps are tiny (less than 5 megs, often under 1 meg) and removing them will not affect your free space noticably. Larger apps should be more visible, though it may take a few minutes for the app manager to finish cleaning up after them. As for "Other", that's mostly stuff like the local email cache (reduce the number of folders you sync and how long you store mail for to reduce this value) and downloaded files and so on.

To be honest I will never buy a phone with less than 16GB storage, 8GB or even 4GB on WP8 is just a joke, Never had this problem with my WP7 Lumia.
The other storage issue is a problem which will hopefully be rectified in an upcoming update, Even with 32 GB on my Lumia I still have nearly 1GB other storage after using Storage Check/Clean up, I believe it is from uploading pics to Sky Drive and of course other temp stuff but it would be great to be able to free this space, Fingers crossed it will get sorted soon

AndyFZ1S said:
To be honest I will never buy a phone with less than 16GB storage, 8GB or even 4GB on WP8 is just a joke, Never had this problem with my WP7 Lumia.
The other storage issue is a problem which will hopefully be rectified in an upcoming update, Even with 32 GB on my Lumia I still have nearly 1GB other storage after using Storage Check/Clean up, I believe it is from uploading pics to Sky Drive and of course other temp stuff but it would be great to be able to free this space, Fingers crossed it will get sorted soon
Click to expand...
Click to collapse
Exactly, less than 8gb WP8 will be useless if other on storage will not be fixed.
Some news says that the other on storage will have an improvement on this coming GDR2 update, I doubt that it will be totally fixed, since they say that its just an improvement.
I think No, I did'nt use skydrive, but the other on storage, grew up to almost 1gb.
History on Internet Explorer/Search also contributes to the growth of the Other on storage, deleting history may free up a 100mb/wk on my WP.
Thank you,

My 521 has 8gb and still has like 3gbs of space left. I have a bunch of games and a couple of albums on the SD card.
Sent from my RM-917_nam_usa_100 using XDA Windows Phone 7 App

[Q] Windows Phone 8 Ram Vs android Ram

Hi ,
I have andorid right now , and looking forward to buy an windows phone 8.
i have android having 512 mb ram. im looking forward to buy Nokia lumia 520. also have 512 ram.
i want to know how much the windows phone allow to use ram. will all apps will work on it like on android. doesnt matter , i only want some apps like viber , whats app and fb to work in background.
Should i buy ram 512 mb phone ?

shanalikhan said:
Hi ,
I have andorid right now , and looking forward to buy an windows phone 8.
i have android having 512 mb ram. im looking forward to buy Nokia lumia 520. also have 512 ram.
i want to know how much the windows phone allow to use ram. will all apps will work on it like on android. doesnt matter , i only want some apps like viber , whats app and fb to work in background.
Should i buy ram 512 mb phone ?
Click to expand...
Click to collapse
if "to work in background" means you want to get push notificiations then: yes and no. windows phone 8's push service is a mess, even if your phone had 512GB of RAM, facebook won't push anything.

Eh? The WP7 version of Facebook did push just fine with 512MB. Not sure about the WP8 version but it *could* work.
Facebook and Twitter and so on will do their integration thing just fine without apps or push notifications anyhow.
With that said, there are definitely apps that won't run on 512MB WP8 devices, but not many, and they're mostly the really big fancy graphically intensive games that the Lumia 520's CPU/GPU would probably struggle with anyhow (not sure if you're aware, but it's basically the entry-level WP8 device).

GoodDayToDie said:
Eh? The WP7 version of Facebook did push just fine with 512MB. Not sure about the WP8 version but it *could* work.
Click to expand...
Click to collapse
The push service of the facebook app was (and still is) a horrible mess. It generally worked, with the exception of message notifications. I never received any message notifications at all, only if someone liked my status, posted in a group etc. Those worked reliable, though.

i heard the in Wp8 , developers are more attracted to set 1GB rams for ther applications. later on they set to 512mb.
so should i buy wp8 with 512mb ? will it run about 85-90% apps ?

512ram on WP8 is like 1gb ram on android its not like android when you run apps just press back until it gets to homescreen and it close all process and it didnt get slow!

how many apps in market is able to run on wp8 , can you estimate , 60% , 70% or 90%
I have htc explorer right now and its working fine on 512mb

Probably well over 90% of apps will run on 512MB phones. The 1GB restriction is mostly only present for high-end games.

There were a few instances of regular Apps not being able to work on 512 MB devices but those got fixed in an update quickly and mostly affected Apps just updated from WP7 to an optimized WP8 version and that had opted out of 256 MB devices on WP7 (so I suppose they forgot to take the limit entry out - it meant "no 256 MB devices" in WP7 but in a WP8-App the same entry limits it to 1 GB devices). Aside from that as has already been said it mostly affected games and quite a lot have been updated to work on 512 MB as well (Asphalt 7 and Temple Run are 2 notable examples).
As for background processing. 180 MB is the maximum a WP8 App may use on 512 MB devices (it was limited to 90 MB max on WP7). There is a set amount of background tasks that can be configured to run that is dependent on the device but regularly scales with the amount of memory available. Apps that are not in the foreground are dormant and are removed from memory if a more recently used App requires the memory. Many Apps like WhatsApp do employ the push service which does not require the actual App to run in the background so those aren't affected by the limitations outlined above.

Phone 8
WP 8 handles less RAM better than Android. This correspondes to the better optimation of the OS.