I seriously doubt Xbox 360's ability to do 1080p

Wouldn't the fact that this bandwidth has to be shared between CPU and GPU
have some sort of effect? PC video cards have dedicated video memory -- they
don't share it. The 360 has to share this bandwidth and I'll bet the GPU has
to access this shared memory *frequently*.

--
Doug
"Martin Linklater" wrote in message
news:[email protected]

3GB/sec is a trivial bandwidth for CPU-GPU hardware. That's not a problem
at all.

On 2006-09-30 09:53:11 +0100, "pigdos" said:

Wouldn't the fact that this bandwidth has to be shared between CPU and
GPU have some sort of effect? PC video cards have dedicated video
memory -- they don't share it. The 360 has to share this bandwidth and
I'll bet the GPU has to access this shared memory *frequently*.

It's been designed with high speed CPU/GPU access in mind. I've not got
the exact numbers to hand but I know that the original XBox had 6.4
GB/s memory bandwidth which was shared between the CPU and GPU. Since
the 360 is considerably more advanced that the original XBox I would
presume 3 GB/sec bandwidth between the CPU and the graphics mem is not
a problem. Consider that you can buy things like upscaling DVD players
which can output 1080p - they are basically performing the same task..
ie decompressing the data and copying it all up to a RAM buffer at 50Hz
or whatever. The XBox is considerably more powerfull than your average
upscaling DVD player.


--
Gamertag: FizzyChicken

Bus contention would still be a problem, the GPU and CPU cannot be accessing
system memory simultaneously. For one thing, the more pixels we're pushing
the more AA has to be performed. I'll bet this is one of the reasons the 360
can't do more than 2xAA, and can't do Adaptive AA or temporal AA at all.
Does the 360 do any anisotropic filtering at all?

--
Doug
"Martin Linklater" wrote in message
news:[email protected]
On 2006-09-30 09:53:11 +0100, "pigdos" said:


It's been designed with high speed CPU/GPU access in mind. I've not got
the exact numbers to hand but I know that the original XBox had 6.4 GB/s
memory bandwidth which was shared between the CPU and GPU. Since the 360
is considerably more advanced that the original XBox I would presume 3
GB/sec bandwidth between the CPU and the graphics mem is not a problem.
Consider that you can buy things like upscaling DVD players which can
output 1080p - they are basically performing the same task.. ie
decompressing the data and copying it all up to a RAM buffer at 50Hz or
whatever. The XBox is considerably more powerfull than your average
upscaling DVD player.


--
Gamertag: FizzyChicken

On 2006-10-02 15:43:02 +0100, "pigdos" said:

Bus contention would still be a problem, the GPU and CPU cannot be
accessing system memory simultaneously.

It depends on how many DMA channels there are. The original XBox had 4
so I wouldn't expect the 360 to have any trouble with this.

For one thing, the more pixels we're pushing the more AA has to be
performed. I'll bet this is one of the reasons the 360 can't do more
than 2xAA, and can't do Adaptive AA or temporal AA at all. Does the 360
do any anisotropic filtering at all?

Yes. Even the original XBox had anisotropic filtering.
--
Gamertag: FizzyChicken

All DMA implies is that the CPU doesn't have to get involved in
device-to-memory transfers, obviously this is a good thing, but it doesn't
do much for the fact that the GPU is processing MASSIVE amounts of data from
system memory. Hell, even AGP memory was relegated to mere texture storage,
but in the 360 everything the GPU processes is in system memory. Anisotropic
filtering, AA, textures, per pixel lighting/shading all of these involve the
GPU reading/writing to system memory. Some of these operations can't even be
done in one-pass which only adds to system memory thrashing.

It's too bad no one can verify MS's marketing "specifications" about the
360. I'd love to see some SPECint or SPECfp benchmarks for the 360 or even
some memory benchmarks for that matter.


--
Doug
"Martin Linklater" wrote in message
news:[email protected]
On 2006-10-02 15:43:02 +0100, "pigdos" said:

Bus contention would still be a problem, the GPU and CPU cannot be
accessing system memory simultaneously.

It depends on how many DMA channels there are. The original XBox had 4 so
I wouldn't expect the 360 to have any trouble with this.

For one thing, the more pixels we're pushing the more AA has to be
performed. I'll bet this is one of the reasons the 360 can't do more than
2xAA, and can't do Adaptive AA or temporal AA at all. Does the 360 do any
anisotropic filtering at all?

Yes. Even the original XBox had anisotropic filtering.
--
Gamertag: FizzyChicken

On 2006-10-03 03:29:39 +0100, "pigdos" said:

All DMA implies is that the CPU doesn't have to get involved in
device-to-memory transfers, obviously this is a good thing, but it
doesn't do much for the fact that the GPU is processing MASSIVE amounts
of data from system memory. Hell, even AGP memory was relegated to mere
texture storage, but in the 360 everything the GPU processes is in
system memory. Anisotropic filtering, AA, textures, per pixel
lighting/shading all of these involve the GPU reading/writing to system
memory. Some of these operations can't even be done in one-pass which
only adds to system memory thrashing.

It's too bad no one can verify MS's marketing "specifications" about
the 360. I'd love to see some SPECint or SPECfp benchmarks for the 360
or even some memory benchmarks for that matter.

After about 0.01 nanoseconds on Google I found this:

http://features.teamxbox.com/xbox/11...-Dissected/p6/

GPU-Graphics RAM bandwidth = 256GB/s
Main memory bandwidth = 22.4 GB/s

Kinda makes that 3GB/s 1080p spec seem trivial eh ?
--
Gamertag: FizzyChicken

"Martin Linklater" wrote in message
news:[email protected]
On 2006-10-03 03:29:39 +0100, "pigdos" said:

All DMA implies is that the CPU doesn't have to get involved in
device-to-memory transfers, obviously this is a good thing, but it
doesn't do much for the fact that the GPU is processing MASSIVE amounts
of data from system memory. Hell, even AGP memory was relegated to mere
texture storage, but in the 360 everything the GPU processes is in system
memory. Anisotropic filtering, AA, textures, per pixel lighting/shading
all of these involve the GPU reading/writing to system memory. Some of
these operations can't even be done in one-pass which only adds to system
memory thrashing.

It's too bad no one can verify MS's marketing "specifications" about the
360. I'd love to see some SPECint or SPECfp benchmarks for the 360 or
even some memory benchmarks for that matter.

After about 0.01 nanoseconds on Google I found this:

http://features.teamxbox.com/xbox/11...-Dissected/p6/

GPU-Graphics RAM bandwidth = 256GB/s
Main memory bandwidth = 22.4 GB/s

Kinda makes that 3GB/s 1080p spec seem trivial eh ?
--
Gamertag: FizzyChicken

You what Love?

Duh, the 256GB/s is to 10MB of EDRAM. It's basically a glorified
framebuffer. How many textures can you store in 10MB? I don't think you can
even process ANY form of AA at 1080p in 10MB (hint AA involves sampling MORE
pixels than are acutally present, some forms of AA require 6 times the
amount of data per pixel, per color, to be useful it should be 4 times the
number of pixels present [which for 1080p won't fit in 10MB of anything).
Guess you've got a lot to learn don't you?

--
Doug
"Martin Linklater" wrote in message
news:[email protected]
On 2006-10-03 03:29:39 +0100, "pigdos" said:

http://features.teamxbox.com/xbox/11...-Dissected/p6/

GPU-Graphics RAM bandwidth = 256GB/s
Main memory bandwidth = 22.4 GB/s

Kinda makes that 3GB/s 1080p spec seem trivial eh ?
--
Gamertag: FizzyChicken

On Tue, 03 Oct 2006 18:37:30 GMT, "pigdos" wrote:

Duh, the 256GB/s is to 10MB of EDRAM. It's basically a glorified
framebuffer. How many textures can you store in 10MB? I don't think you can
even process ANY form of AA at 1080p in 10MB (hint AA involves sampling MORE
pixels than are acutally present, some forms of AA require 6 times the
amount of data per pixel, per color, to be useful it should be 4 times the
number of pixels present [which for 1080p won't fit in 10MB of anything).
Guess you've got a lot to learn don't you?

yeah martin, get a clue about programming!
--

gamertag: Chrisflynnuk
http://live.xbox.com/member/Chrisflynnuk
Current eBay auctions: http://tinyurl.com/hutcb

pigdos wrote:
Duh, the 256GB/s is to 10MB of EDRAM. It's basically a glorified
framebuffer. How many textures can you store in 10MB? I don't think you can
even process ANY form of AA at 1080p in 10MB (hint AA involves sampling MORE
pixels than are acutally present, some forms of AA require 6 times the
amount of data per pixel, per color, to be useful it should be 4 times the
number of pixels present [which for 1080p won't fit in 10MB of anything).
Guess you've got a lot to learn don't you?

Oh dear. You've just gone and messed yourself right up, 'PigDo'.