xbox 360 specs (unofficial, but believable)

[-tkf-]

Re: 40GB

Wont this use VC-1 for encoding? it would seem it has the power?

 

[Titanio]

Getting back to the 9bn dot products per cycle figure, does this reveal any "special sauce" on the vmx units, or is that what you'd expect to get out of 3 standard vmx units at 3.2Ghz (theoretically, of course)?

If a dot product is 4 multiplies and 3 additions, is that 7 floating point ops? So taking nAo's figure of 76.8Gflops, 76.8/7 = ~11bn dot products? Or if you round up to 8 flops (which you probably would do..can't do much with that extra spare flop per cycle per core..at least not another dot product), 76.8/8 = ~9bn? Is that were it comes from, or am I totally off track?

 

[Carl B]

128 bit bus enables them to reduce 512Mbit chips * 8 to 1Gbit chips * 4 when cheaper 1Gbit chips get available a few years later. Then they can retool the motherboard more simpler, and cheaper.

BTW, 256 GB/s memory bandwidth to EDRAM means it uses 4096bit bus running at 500Mhz if the GPU is a single chip.

Great point.

 

[version]

Getting back to the 9bn dot products per cycle figure, does this reveal any "special sauce" on the vmx units, or is that what you'd expect to get out of 3 standard vmx units at 3.2Ghz (theoretically, of course)?

If a dot product is 4 multiplies and 3 additions, is that 7 floating point ops? So taking nAo's figure of 76.8Gflops, 76.8/7 = ~11bn dot products? Or if you round up to 8 flops (which you probably would do..can't do much with that extra spare flop per cycle per core..at least not another dot product), 76.8/8 = ~9bn? Is that were it comes from, or am I totally off track?

you are right
cell 320Gflops / 8 = 40

 

[nAo]

My calculations assumed 8 ops per clock, I believe VMX units can do one fmadd per cycle.

 

[j^aws]

Sorry I havnet been keeping up with the specs as much as I like, so MS went ahead and went for the 512 ram?

If this spec is true then yes, 512MB is good.

Memory
-512 MB GDDR3 RAM
- 700 MNz DDR

Memory Bandwidth
- 22.4 GB/s memory interface bus bandwidth
- 256 GB/s memory bandwidth to EDRAM
- 21.6 GB/s frontside bus

700 MHz DDR (1400 MHz effective)

22.4 GB/s --> 128 bit bus

I was hoping it would be 256 bit ---> 44.8 GB/s

128 bit bus enables them to reduce 512Mbit chips * 8 to 1Gbit chips * 4 when cheaper 1Gbit chips get available a few years later. Then they can retool the motherboard more simpler, and cheaper.

If they launch with 8 DRAM chips with a 128 bit bus, then that sets a precedent for Sony and Nintendo to follow with that config, at least from a cost, heat and mobo traces POV it would seem feasable.

BTW, 256 GB/s memory bandwidth to EDRAM means it uses 4096bit bus running at 500Mhz if the GPU is a single chip.

I'm pretty sure that 256 GB/s is 'effective' bandwidth and not 'true' bandwith as mentioned in the original 'leak'.

 

[Mythos]

Mpeg4 support?

 

[Megadrive1988]

BTW, 256 GB/s memory bandwidth to EDRAM means it uses 4096bit bus running at 500Mhz if the GPU is a single chip.

I'm pretty sure that 256 GB/s is 'effective' bandwidth and not 'true' bandwith as mentioned in the original 'leak'.

I'm pretty sure that 256 GB/s is 'effective' bandwidth and not 'true' bandwith as mentioned in the original 'leak'.[/quote]


yeah - the 256 GB/sec EDRAM bandwidth effective bandwidth was mentioned back in... no later than June 2004, and possibily earlier.

quote: Xenon Hardware Overview

Eight pixels (where each pixel is color plus z = 8 bytes) can be sent to the EDRAM every GPU clock cycle, for an EDRAM write bandwidth of 32 GB/sec. Each of these pixels can be expanded through multisampling to 4 samples, for up to 32 multisampled pixel samples per clock cycle. With alpha blending, z-test, and z-write enabled, this is equivalent to having 256 GB/sec of effective bandwidth! The important thing is that frame buffer bandwidth will never slow down the Xenon GPU.

http://forums.xbox-scene.com/index.php?showtopic=231928
http://www.beyond3d.com/forum/viewtopic.php?t=13470
http://www.google.com/groups?selm=51488ce2.0406222254.5a7434a9@posting.google.com&output=gplain

 

[Megadrive1988]

I'm still holding out hope that with a 256-bit bus, the main memory/system bandwidth will be double or roughly 2.5x greater than the ~22 GB/sec which is because of a 128-bit bus.

the old, old reported main memory bandwidth which was ~51 GB/sec, would be nice
(the one BEFORE the leaked Xenon Diagram and Hardware Overview)

This VPU is being designed with the latest technologies in mind, such as GDDR2 SDRAM memory provided by Samsung running at 1600 MHz. A 128-bit configuration is capable of providing up to 25.6 GB/s peak bandwidth, while its 256-bit mode brings up to a shocking 51.2GB/s peak bandwidth!!! Samsung’s GDDR2 256-megabit memory will enable graphics memory cards of 512 MB, althought it is impossible to confirm if the Xbox 2 will feature such amount of system memory.

a 128-bit bus is kinda disappointing since R300 in Radeon 9700 has had 256-bit since 2002. (as did other new G|VPUs of 2002)

 

[jvd]

a 128-bit bus is kinda disappointing since R300 in Radeon 9700 has had 256-bit since 2002. (as did other new G|VPUs of 2002)

most of the mid to low end boards still have only a 128-bit bus .

THe 9700 had one but was phased out before it hit 200$ and all the other boards from both ati and nvidia were 128 and lower


Though i would think it would have a 256bit bus now . In the future they could allways just use a 128bit buss with the faster ram .

 

[Megadrive1988]

but all *highend* ATI VPUs and Nvidia GPUs have 256-bit bus, or am I mistaken ?

 

[nAo]

I'm still holding out hope that with a 256-bit bus, the main memory/system bandwidth will be double or roughly 2.5x greater than the ~22 GB/sec which is because of a 128-bit bus.

R300 didn't have a 48 (256) GB/s extra bus dedicated to render targets.

 

[jvd]

but all *highend* ATI VPUs and Nvidia GPUs have 256-bit bus, or am I mistaken ?

But a high end board was 1 gpu with 256 megs of ram . Not a gpu , tri core cpu , 512 megs of ram , 10+ edram , sound chip , wifi and whatever else is in there like controler ports , usb and crap .

Huge diffrence .

256bit bus will never scale down in price slower than faster ram if it scales at all. It would also make the mainboard have more layers than needed which = higher costs .

But even i was thinking just southof 50 for main ram bandwidth

 

[Megadrive1988]

I'm still holding out hope that with a 256-bit bus, the main memory/system bandwidth will be double or roughly 2.5x greater than the ~22 GB/sec which is because of a 128-bit bus.

R300 didn't have a 48 (256) GB/s extra bus dedicated to render targets.

that's true, and I was going to add "but the EDRAM bandwidth offsets the relatively small main memory bandwidth" so it's all good >_<

 

[vliw]

Anyway guys, are those specs like......Good enough for next gen? Do they this years high end pcs or something like that?

It's a Low Cost Next gen, imho....Ps3 will be another world.

 

[Dave Baumann]

Anyway guys, are those specs like......Good enough for next gen? Do they this years high end pcs or something like that?

It's a Low Cost Next gen, imho....Ps3 will be another world.

How do you fathom "low cost"?

 

[jvd]

How do you fathom "low cost"?

In his mind where a 500$ system is low cost and a 500$ six months later will be a high cost system. ONly really because it says sony on it and not microsoft.

 

[hey69]

lowcost as in 2-4 times less powerfull

 

[darkblu]

My calculations assumed 8 ops per clock, I believe VMX units can do one fmadd per cycle.

that sounds absolutely in-line with the 1 dp per cycle info : )

 

[fxtech]

i immagine vliw means low budget tech low cost hardware compared to the other hardware producer , not low cost retail price