Middle Generation Console Upgrade Discussion [Scorpio, 4Pro]

[Deleted member 11852]

I saw rumoured leaked specs of the 1080Ti having 12GB GDDR5X. Which seems totally plausible to me. And people think new Xbox will have 32GB HBM2?!

Only if it's stupidly cheap which it isn't. It's a cheaper alternate to GDDR5/X in volume but that's not the same thing. Nvidia have shipped 12Gb Quadro and Titan cards for a while but the focus for the 1080 was boosting raw performance. There are few games that will utilise 8Gb GDDR5 and 16Gb DDR and you want to put 25% more in? For what?

I can see a 12Gb 1080Ti but not a 32Gb Xbox. At least not the next Xbox.

 

[Shifty Geezer]

I do mean working RAM.

then it's not a few fringe devices in the console and gaming space.

PS3 used split memory not because it was preferable but because there was no choice.

That's true of every split pool device, including PS3, PC, XB1, PS2. The cheap, high capacity RAM isn't fast enough for wroking; the fast RAM isn't cheap enough. So a large number of gaming-focussed products use at least two pools of RAM to compromise between RAM performance and RAM cost.

 

[Deleted member 11852]

then it's not a few fringe devices in the console and gaming space.

I didn't limited my fringe case statement to the console space Even if you take it wider to the gaming space unified memory systems are cheaper than split memeoru systems - again, all things being equal. It's why integrated graphics chips using mainboard DDR3/DDR4 are so common.

That's true of every split pool device, including PS3, PC, XB1, PS2. The cheap, high capacity RAM isn't fast enough for wroking; the fast RAM isn't cheap enough. So a large number of gaming-focussed products use at least two pools of RAM to compromise between RAM performance and RAM cost.

I'm not seeing it. Not unless you go back a number of years. Technology marches on, conventional wisdom even five years ago will be different to today.

 

[Shifty Geezer]

I didn't limited my fringe case statement to the console space

Not much reason to compare the RAM requirements of a phone or TV or washing machine with a gaming console when they clearly have different requirements.

I'm not seeing it. Not unless you go back a number of years.

It's the opposite. In the earliest days of computing everything ran from RAM, even before caches. Nowadays we prefer split pools on the whole for performance parts (discounting caches). Intel has eDRAM along with system DDR, so even your pokey netbook has split pool for the integrated graphics. Every GPU has its own memory, and we can't replace the system RAM with stacked RAM and have a single pool for everything until maybe a future APU? But your 'fringe' cases are the vast majority of gaming platforms made in the past ten years. I think only PS4 counts a unified memory solution in that timeframe. Go back another generation and you can add OXB in contrast to PS2, GC and Saturn which all used split RAM.

It's very much a case of unified memory being the rare outlier.

 

[Rodéric]

Except mobiles and tablets of course, they have a single pool of memory...

 

[rockaman]

Isn't the Xbox 360 and Xbone larger pools of RAM also unified though? The 512 MB GDDR3 and 8 GB DDR3 I mean.

Even though they have another EDRAM/ESRAM pool, but the rest was also accessible directly to the GPU and CPU wasn't it?

Effectively they were like unified RAM pools also, but with an extra small RAM pool mainly for framebuffer and shader/fullscreen effects I thought.

 

[Shifty Geezer]

Except mobiles and tablets of course, they have a single pool of memory...

Already mentioned, and they aren't designed for performance gaming, and they use TBDR to circumvent some of the BW issues too.

 

[Deleted member 11852]

It's the opposite. In the earliest days of computing everything ran from RAM, even before caches.

Sure, in the early days you had a valve and later a drum.

Nowadays we prefer split pools on the whole for performance parts (discounting caches). Intel has eDRAM along with system DDR, so even your pokey netbook has split pool for the integrated graphics. Every GPU has its own memory, and we can't replace the system RAM with stacked RAM and have a single pool for everything until maybe a future APU? But your 'fringe' cases are the vast majority of gaming platforms made in the past ten years. I think only PS4 counts a unified memory solution in that timeframe. Go back another generation and you can add OXB in contrast to PS2, GC and Saturn which all used split RAM.

The Xbox One also has unified RAM. EDRAM and ESRAM are scratchpads, or a cache if you prefer. But split pools are definitely not a preference, they're a consequence of the PC architecture where two (or more) high performance parts like CPU and GPU are separated by the slow PCI bus.

With more and more being pushed onto the GPU (and off the CPU) VRAM demand will grow and CPU-function memory requirements may even drop for gaming because Compute is developing faster and faster and subsuming tasks tradiotnally undertaken on a general processor and doing them in a fraction of the time.

You'll likely reach the point where a single pool of very fast DRAM with a nexthgen onion/garlic bus or low-end InfiniBand will offset separate memory pools - it just won't bedworth it for relatively low amount of CPU-only RAM. We saw the same thing in server architectures, but you need to break conventional PC architecture to make it happen.

Split memory pools are old ways of thinking. That was a solution to a specific problem, the economics probably favour it in some cases and not in others depending on your use case scenario. But as a rule of thumb, two memory controllers, two buses and increased PCB complexity is not a good cost/engineering tradeoff to save a little bit on RAM. Depending on RAM prices at any given time. GDDR5 has plummeted in recent years, DDR4 is still relatively expensive. It's like like four years back when there was a gulf between GDDR5 and DDR3.

 

[Shifty Geezer]

The Xbox One also has unified RAM. EDRAM and ESRAM are scratchpads, or a cache if you prefer.

That's what I was saying about working RAM. If one doesn't include these types of scratchpad memories than yes, most use single RAM pools. However, as long as the RAM system cannot provide performance and capacity and economy, which currently none can, we need to augment this RAM with some other flavour of RAM beyond processor caches, whether separate VRAM or some high performance, low capacity scratchpad like eDRAM. And regards a new console design, the choice is eDRAM or GDDR (+DDR) until HBM becomes an option.

 

[Rikimaru]

I was thinking of any splut memory, but I suppose you mean main storage and not working RAM. Certainly very few devices focussed on performance have operated from a single pool of memory. PC has split pool, PS3 did, XB360 did (eDRAM pool), XB1 does, PS2 did, GC did, etc. A single pool of RAM providing adeqaute storage and bandwidth is hard to clearly hard to come by. Butif one doesn't mean working RAM, then yes, a single pool of memory with one RAM type is the preferred option.

Embedded cache is in entirely different category.

 

[function]

The cheapest consoles of every generation tend to be from Nintendo, and they certainly do love them some split memory pools. This gen it's only Sony that have gone for fully unified memory, and the huge GDDR5 interface may end up being a barrier to a shrink - or at least make it far less cost effective. They've been so successful they may just end up laughing it off though.

 

[Deleted member 11852]

BTW Wi U has 2Gb DDR3 split between CPU and GPU. There is some EDRAM in there but a scratchpad isn't memory. It's a cache for the memory.

 

[Globalisateur]

Natural selection applied to memory architecture:

- Unified memory pool without scratchpad won easily against 2 competitors using a scratchpad. It can't be a total coincidence. I'd be very surprised indeed to see a scratchpad in any future MS or Nintendo new generation of home console.

 

[Shifty Geezer]

Scratchpad won't be necessary with HBM. The only reason for split pool might be if not enough RAM can be stacked, or CPU + HBM in APU config has significant issues, at which point we'll have a VRAM + sysRAM topology.

 

[function]

BTW Wi U has 2Gb DDR3 split between CPU and GPU. There is some EDRAM in there but a scratchpad isn't memory. It's a cache for the memory.

AFAIK, the WiiU memory isn't split between GPU and CPU - there's 1GB pool for games and another for the OS. Both access memory throught he same 64-bit bus. The edram is an evolution of the main working memory for the Wii - so I guess what you would classify it as depends on what you're using it for. There's another small pool of edram on the WiiU chip too - maybe legacy mode framebuffer?

 

[Shifty Geezer]

We don't need to argue about what to call the eDRAM. I originally specified we can discount that if we want, and that's what everyone's doing. So 'unified memory' is just talking about the main, many GBs, RAM and not specific working-space RAM and all consoles are using 'unified memory'.

 

[function]

I'm not too worried about what we call scratchpad or not - it's what you've got and what you do with it that matters ultimately.

One good argument against embedded memory on the nextbox GPU might be that it would only make sense if paired with DDR4 ... which may be too slow for doing compute work on large datasets, even if the embedded memory was super fast. LPDDR4 is much faster, but probably more expensive (and do AMD have a LPDDR4 controller?).

 

[Deleted member 11852]

AFAIK, the WiiU memory isn't split between GPU and CPU - there's 1GB pool for games and another for the OS. Both access memory throught he same 64-bit bus.

Yeah, I should have have shared. That's my point - it's another example of shared memory system. Split memory systems really only exist for legacy performance reasons.

 

[Shifty Geezer]

So if not for the poor connection between GPU and CPU on PC, we'd have PCs with 20+ GBs of unified GDDR5 accesed by both processors?

 

[BRiT]

It already happens if you consider PC to mean Personal Console.