Shared RAM vs VRAM info please

[azpatrick]

Can anyone point me to a good article about the performance difference between using Shared RAM for the video vs. dedicated VRAM? Thanks! Pat Davis

 

[VBboy]

What videocards/chipsets are you comparing? For example, there are no GeForce2/3 that use share RAM (unless you count AGP texturing).

Specify which videocards you're comparing to do an Apples to Apples comparison.

 

[BFG10K]

The performance difference vs shared memory and dedicated memory is massive. Avoid shared memory accelerators if you plan on playing any 3D games.

 

[azpatrick]

Sorry about the confusion. My question is actually simpler than that. My employer had a 'demo CD' made that uses WinDVD to present an MPEG2 video. The people that created this for us say the requirements are 'a PIII'. I ordered notebook computers for the sales team before knowing of this 'requirement', ordered IBM Thinkpad Celeron 700 with 128MB RAM and 8M Shared Video (didn't know this at the time but . . .). Anyway the presentation will not run very well on this machine - but I have an old Compaq 6500 PII 300 128M RAM 4M Video that runs the presentation fine.

They are telling me I can't watch the video on the IBM because it is a Celeron and I am saying I believe it is slow because of the shared ram rather then dedicated video ram. I am not sure if the Celeron 700 is the Coppermine 128 with the 100mhz FSB or not, I don't think that matters, my PII 300 is a 66mhz bus so that should not be the issue.

Therefore I am searching for information to prove or disprove my shared RAM theory.

I do not have access to the IBM right now to see what video card it uses. I do know that when I check the My_Computer properties, it shows 120MB RAM installed though there is 128. My rep at CDW told me that most of the notebooks they sell are also shared rather than dedicated video RAM.

Hope this is more information that you needed. thanks!

Pat Davis

PS - found out the video card is Trident Cyberblade AGP.

 

[uhohibrokeit]

shared ram not only takes away some of your system memory... it is MUCH MUCH slower for your video to access the ram... since it doesnt have direct access to it

 

[azpatrick]

I totally agree, I have to find some documentation trying to prove my problem is with the shared video RAM rather than the Celeron 700.

thanks!

 

[VBboy]

The problem here is not the shared memory.

It's most likely the sorry-ass video chipset used in the Celery. It most likely has no DVD hardware assist whatsoever, meaning the CPU has to do all the work related to decoding and displaying the movie. Normally, all modern videocards feature some form of hardware decoding assistance, so the CPU load is minimized. Memory itself only needs to be fast enough to display 30 frames per second, but even 20 frames per second would do. There is very little data that needs to be moved from main memory to the videocard - nothing compared to games. It is the video chipset that is too slow, so the CPU has to do all the work, and even that celery 700 is having a hard time doing it.

** You can buy a hardware DVD decoder that goes into a PCMCIA slot - probably much cheaper than the shipping + restocking fee on the Celery 🙂

P.S. Never buy anything with shared memory 🙂

 

[azpatrick]

Thanks for the info on the graphics chipset. Do you think the 6500 PII 300 would have hardware decoding? it uses an ATI 3D RAGE LT PRO. It is an old machine, probably 4 years old. I will run the video in both machines and check the CPU utilization. I do know that both DVD drives have DMA enabled.

thanks!

 

[VBboy]

azpatrick,

I am not sure about that particular video chipset, but ATI is famous for having very good DVD-related features built into their videocards. I remember a few years ago they were even promising real-time Mpeg encoding with just a P3-500 or something like that 🙂

Check with ATI to see if the ATI 3D RAGE LT PRO has it.

Note: I have an IBM Celery (I hope the word "celery" doesn't offend anyone) 466 with a Rage Mobility 8 MB. It plays DVDs absolutely beautifully.

 

[Kingofcomputer]

The problem here is the integrated video solution - they're normally the cheapy slow video chip onboard or integrated into the chipset for basic display function, not a geforce3 chip.

 

[ViRGE]

The LT PRO was one of ATi's earliest cards to have decoding features. That said, I've seen it in action and it seemed to work well, but I question if it's mature enough to be compared to something like a Raedon or GF2/3 card, which have decoding nailed down tight.