Like I said, you are selling RDNA short, it's pretty much 2x GCN core for core.
8x2=16. 16 GCN CUs isn't much. That's literally what RX 560 was and I owned that card. RX 560 unlike RDNA has very strong compute component and it is excellent at BOINC stuff. RX 560 essentially beat GTX 1060 at double precision computing, which is what is the main performance metric for projects like MilkyWay at home. Right now, RX 560 is beaten by 20% by RTX 3060. Not bad. Anyway, RX 560 at one point was a great card. It does run CoD WW2 at 1440p, low with max textures and some AA at 30-60 fps. GTA 5 runs at 1440p medium-high average at 45-50 fps. And RX 560 model without 6 pin connector was TDP limited to just 37.5 watts (I had this model). That's quite impressive. A whole computer with i5 10400F and RX 560 idles at around 30 watts and uses around 100 watts in games. But that was with RX 560 and with games from 2015-2017. Today RX 560 4GB is only good for 900p or 720p low at 50 fps. And RX 560 4GB has dedicated GDDR5 128 bit VRAM clocked at 1750 MHz and 4 GB of it, Deck only has shared 16GB of LPDDR5 at unknown frequency. All things considered, likely 2GB or 3GB is allocated to graphics. Also Steam states that in FP32 (single precision floating point operations) that APU achieves up to 1.6 teraflops. Up to means that it varies due to power limitations, temperature limitations. Meanwhile RX 560 4GB, achieves 2.611 teraflops. So I really have no idea where those claims of 20 IPC come from. RX 560 also runs at considerably lower clock speeds, base being 1175 MHz and boost being 1275 MHz. In terms of raw performance, RX 560 should be a lot faster, around 70% faster, but depending on various factors it can be a lot faster (in case of thermal limitations, Deck is supposed to have base clock speed of 1GHz and teraflops were measure at maximum boost of 1.6GHz, so it can lose a lot of performance. Let's take a look at how does RX 560 4GB perform today:
Let's take a closer look at some demanding titles, average fps and settings:
Apex, 1080p medium (high textures), avg 50 fps
Warzone, 1080p lowest, avg 53 fps
Control, 1080p lowest, avg 44 fps
RDR 2, 1080p lowest, avg 37 fps
Horizon Zero Dawn, 1080p lowest, avg 36 fps
AC Valhalla, 720p lowest, avg 58 fps
Cyberpunk, 720p low, avg 44 fps
So depending on game your experience can be okay, but on most demanding titles, RX 560 really struggles or doesn't struggle, but makes everything looks like potato. And supposedly RX 560 is 80% faster than Deck's RDNA APU (I doubt that it can sustain maximum boost with that reported very generous boost range). So if we do math, we can get how well Deck will perform in same titles, at same settings, assuming no VRAM limitations and no CPU bottleneck, which isn't very realistic, but here's the list:
Apex, 1080p medium, avg 28 fps
Warzone, 1080p lowest, avg 29 fps
Control, 1080p lowest, avg 24 fps
RDR 2, 1080p lowest, avg 21 fps
Horizon Zero Dawn, 1080 lowest, avg 20 fps
AC Valhalla, 720p lowest, avg 32 fps
Cyberpunk, 720p low, avg 24 fps
If we agree that lowest acceptable performance is average 30 fps (it will dip below that) and lowest good performance is 40 fps, then only AC Valhalla runs adequately well at 720p lowest at 32 fps. Obviously, there's not much point (super sampling is always cool, but it's very taxing on any hardware) in running games at 1080p on Deck, so we can calculate performance at 720p, which is basically 2x of 1080p in theory, then our game list looks like this:
Apex, 720p medium, avg 56 fps
Warzone, 720p lowest, avg 58 fps
Control, 720p lowest, avg 48 fps
RDR 2, 720p lowest, avg 42 fps
Horizon Zero Dawn, 720p lowest, avg 40 fps
AC Valhalla, 720p lowest, avg 32 fps
Cyberpunk, 720p low, avg 24 fps
Some games are now running really smooth, but others are just okay and Cyberpunk is still in sub 30 fps zone. If we want to hit 40 fps average, we can calculate performance per pixel and arrive at resolution at which in theory titles should run at 40 fps on Deck. So we are left with AC Valhalla and Cyberpunk, both at low-lowest settings, so there's nothing you can change in visual settings anymore and you only can search for low spec mods or reduce resolution. Reducing resolution is easier solution.
AC Valhalla. 720p is 1280x720, meaning 921600 pixels. We get 32 fps with that. We want 40 fps. So we calculate:
32/40*100 = 80%
We need 20% less pixels, so:
0,8*921600 = 737280
And then according Wikipedia's resolution list (
https://en.wikipedia.org/wiki/List_of_common_resolutions) we get that closest resolution to 737280 pixels is 960x720 (691200 pixels, so we get some performance boost and it's 4:3 aspect ratio, so it might end up being stretched to fit 16:10 screen, if Deck doesn't have good scaler).
Cyberpunk. 720p is 1280x720, meaning 921600 pixels. We get 24 fps with that. We want 40 fps. So we calculate:
24/40*100 = 60%
We need 40% less pixels, so
0,6*921600 = 552960
And using same resolution list, we get that closest resolution is 960x540, which is 518400 pixels, so a bit of fps boost from 40 fps and it's 16:9 aspect ratio resolution, so there might be less stretching or less black bars. And it pretty much ends up being a bit more than half of native resolution of Deck itself.
Is this a good experience on brand new device? For me it's not and over time you will need to go lower and lower just to hit 40 fps or 30 fps average. Also my calculations are only meaningful if performance scales linearly. If there's VRAM limitation or CPU limitation, fps will be lower and there may be some nasty stuttering. If we trust calculations, then we end up at more realistic list, where we try to balance visuals with fps (we want 40 fps average) and we end up with:
Apex, 720p medium-high
Warzone, 720p medium-high
Control, 720p low-medium
RDR 2, 720p lowest
Horizon Zero Dawn, 720 lowest
AC Valhalla, 960x720 lowest
Cyberpunk, 960x540 lowest
If you want to play games on the list, Deck isn't really going to be a nice experience, but I picked some heavier games. Most games are easier to run and should run at higher fps and visual details, but I wanted to see how in theory Deck should perform at its worst. Those are results today and Deck is only running games at 720p (not 1280x800 native) and gets 40 fps. In some cases more, but sometimes a lot less. After a year or two there will be even more demanding games and since we already have to scale down resolution a lot and Deck itself doesn't have very high resolution, let's just say that AAA gaming on Deck will mean Vaseline resolution or just not running them. And that's optimistic. I haven't mentioned that proton has some overhead and that some DRMs are heavy on CPU, so my calculated performance results are really optimistic and it's unknown at what actual clock speed GPU will usually run, I picked 1,5GHz-1,6GHz range, but it's within spec for it to run even at 1GHz. At that point performance won't be nearly close to what I calculated, it will be a lot lower. And for all these reasons, I think that Deck isn't really going to cut it for gaming, but if you are informed customer, well aware of Deck's capabilities and watch benchmark videos, you may be able to play some latest AAA games respectfully well or you should be able to run somewhat older AAA games.
Emulation is mostly decided by CPU single threaded performance. And you need 2 times faster than FX 6300 core, cores ton run some PS2 games emulated. Zen+ had nearly 2 times IPC of FX 6300, but we have Zen 2 cores here. And unfortunately lower clock speed range. It's not going to run all PS2 games well, but with frame skipping some could run. PS3 emulation is not doable at all. So you are left with trouble free emulation of PS1, Dreamcast, PSP, Wii, NDS, GameCube. By trouble free emulation, I meant in performance only, I can't imagine how you could map Nunchuck to Deck's gamepad or emulate dual screens of NDS. So Deck will realistically be good for PS1, PSP, Dreamcast and maybe GameCube. Obviously, all lower end consoles shouldn't be problematic to emulate, but odd controller layouts will not be doable on Deck, those are N64, Sega Master System (Genesis), Sega Saturn, Atari Jaguar and some others. Is this good? It might be good in terms of raw number of titles, but I'm pretty sure that Deck buyer would really want PS2 emulation and it's somewhat painful not to have it run well. Overall, it's fine for emulation, only with minimal limitations.
Is device capable? It's is capable, but nowadays many devices do more and at similar price point. And if you don't pick 64GB model (which should be avoided), it ends up being even more expensive and then competition is even fiercer. At that point it's possible to buy a laptop, which can run PS2 emulation well and get a gamepad for that, Despite all hype, Proton today is still not great. You still lose a lot of your game library. If you ditch Steam OS, you may be able to use Windows, but Valve didn't promise any Windows drivers and Windows will have it's own quite big overhead, higher storage requirements and some actual maintenance requirement and no console UI. Making it less than ideal solution, if not outright broken solution (custom hardware is cool, until you need drivers).
If emulation is ignored, then it would seem almost reasonable to drop display resolution to native 1280x720 or even lower 960x540, to have more performance and better visual quality in games and sometimes to preserve some battery life. Otherwise, Deck will age like milk.
But yes they could have added more cores, given faster ram, stacked ram/cache... its designed to just be enough. not the most powerful. But for most, even some enthusiasts, it will more than enough. I still have high confidence that most AAA games released over the past few years will run at way over 30fps with a mix of high to med settings, and with freesync that will still feel smooth. Most PS4/Xbox One multiplats will be ~60hz and run/look better than either system.
They didn't promise Freesync and I provided my performance analysis of what you could optimistically expect out of Deck. I really don't think that your expectations are realistic for Deck yet, you seem to be overestimating it and expect it to be a lot better than it will actually be. I hope that my preliminary performance analysis will be insightful for you.
That would make the chip a lot more expensive, tbh the chip itself was designed to be cheaper, use less area and doing the things that you are saying would make it impossible to meet Valve pricing target.
I'm sorry, but actual numbers would be nice and from what we know yet, Deck seemingly won't be fast enough to not disappoint hyped up fanbase. Anyway, if I remember correctly Intel released Broadwell with EDRAM. It didn't increase the cost of CPU, but it made like 20% performance difference. I think that it would have been smart of Valve to include something like that.