Xbox One: DirectX 11.1+ AMD GPU , PS4: DirectX 11.2+ AMD GPU what's the difference?

Thanks Shifty...

 

Definitely. When one tile gets swapped out, reorganising the whole tileset to keep it in a neat order relative to the original texture would be pointless in every way! The slide is more indicative of the thought process of the designer, selecting tiles and copying them across methodically to make it easier to keep track of which tiles (s)he's copied and which are still to do.

 

I wonder if any of these limitations have been addressed by tier 2.

 

Partially resident page tables pointing to partially resident textures...

 

I have another question
"The largest possible texture is 16K X 16K X 8K "
why would you want such a thing, as in why would you texture something with 8,000 layers ?

 

3 dimensional textures are for volumes. Have been used for SVO lighting, for example.

 

1M * 1M pixel virtual address space is not that much really. Consider a 4km * 4km terrain for example. 1Mpix / 4096 meters = 256 pixels/meter. Not enough for good closeup quality.

 

Right but that's the rub - as convenient as it is for development, it is irrational to pay the hardware cost to support these ridiculously large address spaces. It is a zillion times less expensive for applications to handle the coarser layers of the mip chain, even if it means having a little overhead in putting borders on things, etc. Obviously handling a few levels in hardware can be viable and pushes the storage overhead of the border pixels to reasonable levels, but it should be a non-goal to handle a 4km * 4km resource in a single, continuous virtual address space. There's absolutely no need for that, and paying the hardware cost in the texture sampler for that many bits is a poor use of silicon.

I know you're probably on the same page here sebbbi but I just feel the need to push a little back on what some people seem to think. You're *always* going to want a software data structure to handle really massive areas... you don't even allocate that all in virtual address space on the CPU because it's a silly use of hardware that was not designed for that purpose. A few layers (64k^2, maybe a few more bits/powers of two) is one thing, but let's keep it in perspective that there are large diminishing returns to going too far with this in hardware. That quote (where was that from by the way?) sums it up nicely.

 

Would the max linear address space be permitted for existing Windows versions?
Isn't it capped out at 44 bits of VA?

 

hmmm strange.
Current processors cap at 48 bits, why would they use 44 when you forcefully need to use the 48th for the kernel start-up address space in canonical form? You need to put up the page-table any way, since it cant have holes.

aah, you refer to the VA for GPU. Yet, I miss why windows would limit it to 44 bits out of 48?

 

It seems to be a historical remnant of earlier x86-64 designs that could only compare and swap 8 bytes. Windows used that operation for low-overhead updates to linked lists.
64-bit addressing bloated the pointer to the next entry in the list, pushing the total past 8 bytes. This meant updates couldn't be atomic.
Shaving data payload, adding alignment, and making an assumption based on whether the code was in kernel mode or not allowed them to claw their way to 44 bits.

http://www.alex-ionescu.com/?p=50

I still see the 44-bit limit being mentioned for current releases, even with wider compare and swap now available.

 

For a texture? No, it's much smaller. There's a large cost to adding address bits to texture units, so they tend to deal with smaller "pointers".

 

This is fixed as of Windows 8.

Since the implementation detail of things like slists should be hidden from you, as long as you yourself don't go mucking about with the high bits it should all be transparent to your own code.

http://msdn.microsoft.com/en-us/library/windows/desktop/ms684121(v=vs.85).aspx

 

I'm sure it has been answered but does the 7900 series support the tier 2 stuff?

 

No, just the 7790 (Bonaire) supports it from the existing cards.

 

fuck -.- -.-
I should flog myself 44 times in a row for this. I should have known that.
At least, it is not the case on *nix variants, which is probably the reason why I forgot this totally...
still I should have known- thank you for the blog's link.

 

Isn´t the XBox One GPU based on Bonaire? (GCN 1.1 Tier 2)

 

Both are apparently based on the same IP pool for the GPU, same with Kabini, Kaveri, and Hawaii. But the XB1 got additions for the memory system (eSRAM), additional support for a few surface formats (no idea, maybe they are supported in all GCN GPUs) and a few customizations (two additional modified DMA engines, some custom audio logic, higher coherent bandwidth and of course the two instead of the single Jaguar module), but where you could argue, that it doesn't pertain to the core GPU IP anymore, but more system integration and northbridge design.

 

The issue is that the Xbox engineers stated that both systems were based on "sea island", we the recent re-badging it is clear that code names at AMD no longer reflect differences in silicon.
Pretty much we have no intel on the matter, Sony said nothing on the matter neither MSFT.

 

What's Tier 2?