PS3 256MB memory limit myth

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#1 Posted by darkfame (970 posts) -

Hi,

I just wanted to kill the myth about the PS3 memory limit. People are still saying only one of the 256MB memory pools are accessible by the Cell. This is simply not true. The Cell can access this memory pool through the bus which the RSX is connected to.

Real life example: In yellowdog linux 6.1 you can use this memory pool as a swap/ram disk, even though the RSX chip itself is not available through the hypervisor.

Link: http://us.fixstars.com/news/2008/2008-11-19.shtml

Yellow Dog Linux v6.1 offers these updates over v6.0:
- Kernel 2.6.27
- GCC 4.1.2
- Cell SDK 3.1
- Firefox 3.0
- OpenOffice 2.3 (v3.0 coming to YDL.net Enhanced soon!)
- X.org 1.4.999 with xrandr 1.2.2
- Dramatically improved, automated wireless config.
- GUI configuration tool for YDL.net.
- Bluetooth support for the PS3 Sixaxis controller.
- Barcelona Supercomputing Center CellSs.
- ps3vram for fast, temp file storage or swap using PS3 video RAM.

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#2 Posted by st1ka (8179 posts) -
well now i can sleep better...
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#3 Posted by CreepyBacon (3183 posts) -

Fascinating stuff.

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#4 Posted by PandaBear86 (3389 posts) -
Yes it can access it, but its not completely optimized as the RAM runs slower.
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#5 Posted by LordQuorthon (5677 posts) -
I can't wait to tell my friends!
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#6 Posted by darkfame (970 posts) -
I can't wait to tell my friends!LordQuorthon
And remember.. you heard it from the SW Mythbusters. :)
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#7 Posted by Cali3350 (16134 posts) -
256mb of memory is more then enough for the logic of a game (and the cell), the biggest issue of the PS3 is the 256mb limit on the RSX Texture storage. The RSx can technically dip into the main system memory but the latency is too high to use in the real world.
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#8 Posted by thegoldenpoo (5136 posts) -
256mb of memory is more then enough for the logic of a game (and the cell), the biggest issue of the PS3 is the 256mb limit on the RSX Texture storage. The RSx can technically dip into the main system memory but the latency is too high to use in the real world.Cali3350
THIS^^^^ the transfer rate would be snail like, like using my system ram instead of my V-ram on my PC (like they do so in integrated graphics). The real point is waht the ps3 actually looks like, not its numbers and stats.
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#9 Posted by Chofee (194 posts) -
Don't you just hate it when people make topic about something they don't even understand..
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#10 Posted by Velocitas8 (10748 posts) -

Don't you just hate it when people make topic about something they don't even understand..Chofee

i.e. pretty much every "technical" thread in System Wars, ever.

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#11 Posted by AnnoyedDragon (9948 posts) -

PS3 users seem to have a fascination for information that is not relevant to their consoles gaming capability, yet nevertheless is presented as evidence of their consoles gaming capability.

Who remembers all the applications of Cell threads?

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#12 Posted by Duckshot (223 posts) -
RAM is not the problem, it is the GPU that causes the bottlenecks. You just have to look at the rendered Resoutions, after all it's just a 7800 GTX. I mean COD4 is only 1200 x 600p - not even the 720 as advertised.
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#13 Posted by heretrix (37792 posts) -
Why wouldn't you be able to access the ram if it's there. I thought it was just that you didn't have access to the entire 512 all at once.
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#14 Posted by yoyo462001 (7535 posts) -
no one ever said the cell couldn't access it, the problem was the GPU had on 256mb of video RAM thus being a bottleneck, even though it can access the system RAM not having the Ram on the GPU still poses problems.
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#15 Posted by skektek (6450 posts) -
256mb of memory is more then enough for the logic of a game (and the cell), the biggest issue of the PS3 is the 256mb limit on the RSX Texture storage. The RSx can technically dip into the main system memory but the latency is too high to use in the real world.Cali3350
This is untrue. The RSX is a TurboCache GPU, it was designed to augment with system RAM. This technique is standard in most notebooks now.
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#16 Posted by 3picuri3 (9618 posts) -

oh god, not this again.

sorry TC, but i trust the experts & developers & my knowledge of how the PS3 works over that link. the PS3 has a memory bottleneck problem. end of story. no myth.

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#17 Posted by adamosmaki (10557 posts) -
[QUOTE="Cali3350"]256mb of memory is more then enough for the logic of a game (and the cell), the biggest issue of the PS3 is the 256mb limit on the RSX Texture storage. The RSx can technically dip into the main system memory but the latency is too high to use in the real world.skektek
This is untrue. The RSX is a TurboCache GPU, it was designed to augment with system RAM. This technique is standard in most notebooks now.

Yes that is true and the notebooks that use this are cheap notebooks with cheap vgas with low memory that dont afford having more memory on the vga due to the cost of extra video memory and the system RAM is much slower than the Vram . Also the article only says that the specific distribution of linux uses the VRAM for temporary storage or swap it doesnt say about using ram as extended vram(at least i havent notice it saying this)
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#18 Posted by foxhound_fox (96695 posts) -
And the 360's CPU and GPU can access its entire 522MB of shared RAM at any time.
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#19 Posted by 3picuri3 (9618 posts) -
And the 360's CPU and GPU can access its entire 522MB of shared RAM at any time.foxhound_fox
indeed. i can't believe this still pops up in SW. dev after dev speak of the memory problems on the PS3 and how they need to bring in 1st party programmers to get past barriers and create workarounds. when do people stop cherry picking tech articles they don't understand and start listening to the actual developers that work with the hardware for a living.
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#20 Posted by hyperboy152000 (4815 posts) -

PS3 users seem to have a fascination for information that is not relevant to their consoles gaming capability, yet nevertheless is presented as evidence of their consoles gaming capability.

Who remembers all the applications of Cell threads?

AnnoyedDragon

im "fascinated" with tech. specs but that still doesnt stop me from knowing when a game looks good on other systems and i dont make excuses when a game looks like trash on the ps3 (multiplats or otherwise)

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#21 Posted by hyperboy152000 (4815 posts) -

[QUOTE="skektek"][QUOTE="Cali3350"]256mb of memory is more then enough for the logic of a game (and the cell), the biggest issue of the PS3 is the 256mb limit on the RSX Texture storage. The RSx can technically dip into the main system memory but the latency is too high to use in the real world.adamosmaki
This is untrue. The RSX is a TurboCache GPU, it was designed to augment with system RAM. This technique is standard in most notebooks now.

Yes that is true and the notebooks that use this are cheap notebooks with cheap vgas with low memory that dont afford having more memory on the vga due to the cost of extra video memory and the system RAM is much slower than the Vram . Also the article only says that the specific distribution of linux uses the VRAM for temporary storage or swap it doesnt say about using ram as extended vram(at least i havent notice it saying this)

i thought only ATI cards had the turbocache capability...but yea i agree vram is so much "better" for gfx related effects, but the cell has been proven to aleveate some of the work load from the RSX, but the ps3 still has a major bottleneck when it comes to using up bandwidth, like others have said

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#22 Posted by iam2green (13991 posts) -
very nice information here. im going to go tell everyone i see.
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#23 Posted by lowe0 (13692 posts) -
- ps3vram for fast, temp file storage or swap using PS3 video RAM.darkfame
Ummm... swap is normally stored on a hard disk. Just because VRAM reads are faster than a hard disk doesn't make them fast enough to use as allocated memory. And even then, the Cell reads from VRAM at 16MB/sec.. I'd imagine that, if reading from swap in large sequential blocks, the hard drive's higher transfer rate would overcome the seek time advantages of using the VRAM. Whether this actually fits the usage pattern for swap depends on how your application uses RAM.
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#24 Posted by skektek (6450 posts) -
[QUOTE="skektek"][QUOTE="Cali3350"]256mb of memory is more then enough for the logic of a game (and the cell), the biggest issue of the PS3 is the 256mb limit on the RSX Texture storage. The RSx can technically dip into the main system memory but the latency is too high to use in the real world.adamosmaki
This is untrue. The RSX is a TurboCache GPU, it was designed to augment with system RAM. This technique is standard in most notebooks now.

Yes that is true and the notebooks that use this are cheap notebooks with cheap vgas with low memory that dont afford having more memory on the vga due to the cost of extra video memory and the system RAM is much slower than the Vram . Also the article only says that the specific distribution of linux uses the VRAM for temporary storage or swap it doesnt say about using ram as extended vram(at least i havent notice it saying this)

If it were true it wouldn't be used in the "real world" would it? What the Guest OS (Linux) does or does not do is a rather moot point as it runs on a hyper visor and all hardware is virtual.
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#25 Posted by TOAO_Cyrus1 (2895 posts) -
Also the PS3 uses somethign like 50MB of man memory and 25MB of VRam reserved for the OS while the 360 uses something like 30MB total. 45-50 extra MB can amke a big difference in such a small memory pool.
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#26 Posted by hyperboy152000 (4815 posts) -

Also the PS3 uses somethign like 50MB of man memory and 25MB of VRam reserved for the OS while the 360 uses something like 30MB total. 45-50 extra MB can amke a big difference in such a small memory pool.TOAO_Cyrus1

actually sony has been decreasing the amount of MB used for the os, its down to about 43MB of main memory and it doesnt use up the vram at all anymore, um atleast thats the jist of what i read over at B3D

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#27 Posted by skektek (6450 posts) -

[QUOTE="adamosmaki"][QUOTE="skektek"]This is untrue. The RSX is a TurboCache GPU, it was designed to augment with system RAM. This technique is standard in most notebooks now.hyperboy152000

Yes that is true and the notebooks that use this are cheap notebooks with cheap vgas with low memory that dont afford having more memory on the vga due to the cost of extra video memory and the system RAM is much slower than the Vram . Also the article only says that the specific distribution of linux uses the VRAM for temporary storage or swap it doesnt say about using ram as extended vram(at least i havent notice it saying this)

i thought only ATI cards had the turbocache capability...but yea i agree vram is so much "better" for gfx related effects, but the cell has been proven to aleveate some of the work load from the RSX, but the ps3 still has a major bottleneck when it comes to using up bandwidth, like others have said

Nvidia = TurboCache ATI = HyperMemory