ToTTenTranz
Member
EDIT:
- The rumors were wrong. The memory controller is 128bit wide.
- The Steam Deck is Awesome at 88GB/s.
- Sorry for the false concerns.
And why is this important?
Because that's extremely low and the iGPU is probably going to be bottlenecked the whole time, eventually making it perform worse than the handhelds that are already in the market.
Valve is only saying they're using LPDDR5 5500MT/s but they're not disclosing the bus width... and I'm reading some sources claiming that the bus is actually 64bit wide.
So at 5500MT/s and a 64bit (8byte) bus, what this means in practice is that the memory bandwidth will be only 5.5*8 = 44GB/s, shared between CPU cores and iGPU.
For example, the Series S has 224GB/s and the PS5 has 448GB/s. The AYA NEO uses LPDDR4X 4266MT/s but with a 128bit bus, meaning it gets 68GB/s, and so do the Intel Tiger Lake handhelds like the OneXPlayer and GPD Win 3.
It's especially bad considering that Zen2 APUs have very little L3 cache (probably only 4MB L3 in Steam Deck), meaning it needs to access the main RAM quite often, which takes bandwidth away from the GPU. In Intel's Tiger Lake case, it has 12MB L3 that the GPU can access too.
Back in 2013 Sony estimated that the PS4's Jaguar CPU cores would take around 20GB/s, and I don't see why the 4-core Zen2 would use less. That would mean the GPU will struggle with some 24GB/s available bandwidth, which is ten times less the bandwidth of a Radeon RX 5500.
Still, I hope the info I'm getting is wrong, or if the specs are missing something like Infinity Cache of sorts.
I'm saying this to level the performance expectations of Steam Deck. If the 44 GB/s bandwidth number is true, it's likely to perform closer to a 1TFLOPs console than a 2 TFLOPs one.
- The rumors were wrong. The memory controller is 128bit wide.
- The Steam Deck is Awesome at 88GB/s.
- Sorry for the false concerns.
Because that's extremely low and the iGPU is probably going to be bottlenecked the whole time, eventually making it perform worse than the handhelds that are already in the market.
Valve is only saying they're using LPDDR5 5500MT/s but they're not disclosing the bus width... and I'm reading some sources claiming that the bus is actually 64bit wide.
So at 5500MT/s and a 64bit (8byte) bus, what this means in practice is that the memory bandwidth will be only 5.5*8 = 44GB/s, shared between CPU cores and iGPU.
For example, the Series S has 224GB/s and the PS5 has 448GB/s. The AYA NEO uses LPDDR4X 4266MT/s but with a 128bit bus, meaning it gets 68GB/s, and so do the Intel Tiger Lake handhelds like the OneXPlayer and GPD Win 3.
It's especially bad considering that Zen2 APUs have very little L3 cache (probably only 4MB L3 in Steam Deck), meaning it needs to access the main RAM quite often, which takes bandwidth away from the GPU. In Intel's Tiger Lake case, it has 12MB L3 that the GPU can access too.
Back in 2013 Sony estimated that the PS4's Jaguar CPU cores would take around 20GB/s, and I don't see why the 4-core Zen2 would use less. That would mean the GPU will struggle with some 24GB/s available bandwidth, which is ten times less the bandwidth of a Radeon RX 5500.
Still, I hope the info I'm getting is wrong, or if the specs are missing something like Infinity Cache of sorts.
I'm saying this to level the performance expectations of Steam Deck. If the 44 GB/s bandwidth number is true, it's likely to perform closer to a 1TFLOPs console than a 2 TFLOPs one.
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