What causes GPU global memory latency?
I was asking myself what causes GPU global memory latency. I mean the global memory works e.g. on a frequency of 1700MHz (e.g.) and has a 352bit lane, this means it can move around 600GB/s. But then everyone states, this is the slowest memory on a GPU and you have around 200 - 800 cycles access time. If your core works with around 1000MHz this means you have around 2us per access, which is much slower than 600GB/s.
Where does this difference come from?
memory gpu latency global
asked Jan 25 at 6:02
Emerson FittipaldiEmerson Fittipaldi
1
add a comment |
I was asking myself what causes GPU global memory latency. I mean the global memory works e.g. on a frequency of 1700MHz (e.g.) and has a 352bit lane, this means it can move around 600GB/s. But then everyone states, this is the slowest memory on a GPU and you have around 200 - 800 cycles access time. If your core works with around 1000MHz this means you have around 2us per access, which is much slower than 600GB/s.
Where does this difference come from?
memory gpu latency global
asked Jan 25 at 6:02
Emerson FittipaldiEmerson Fittipaldi
1
Bandwidth is different from latency. Because GPUs prioritize bandwidth their memory controllers buffer requests and schedule them to reduce idle channel time. Multiple requests can be in-process concurrently; while one request is opening a row in a bank of one DRAM another can be transferring data and many others can be waiting. (Also 200 cycles at 1 GHz is only 200ns not 2µs.) The question deserve a real answer, but this is a quick hint.
– Paul A. Clayton
Jan 27 at 20:13
add a comment |
I was asking myself what causes GPU global memory latency. I mean the global memory works e.g. on a frequency of 1700MHz (e.g.) and has a 352bit lane, this means it can move around 600GB/s. But then everyone states, this is the slowest memory on a GPU and you have around 200 - 800 cycles access time. If your core works with around 1000MHz this means you have around 2us per access, which is much slower than 600GB/s.
Where does this difference come from?
memory gpu latency global
asked Jan 25 at 6:02
Emerson FittipaldiEmerson Fittipaldi
1
I was asking myself what causes GPU global memory latency. I mean the global memory works e.g. on a frequency of 1700MHz (e.g.) and has a 352bit lane, this means it can move around 600GB/s. But then everyone states, this is the slowest memory on a GPU and you have around 200 - 800 cycles access time. If your core works with around 1000MHz this means you have around 2us per access, which is much slower than 600GB/s.
Where does this difference come from?
memory gpu latency global
memory gpu latency global
asked Jan 25 at 6:02
Emerson FittipaldiEmerson Fittipaldi
1
asked Jan 25 at 6:02
Emerson FittipaldiEmerson Fittipaldi
1
asked Jan 25 at 6:02
Emerson FittipaldiEmerson Fittipaldi
1
asked Jan 25 at 6:02
Emerson FittipaldiEmerson Fittipaldi
1
asked Jan 25 at 6:02
Emerson FittipaldiEmerson Fittipaldi
1
1
Bandwidth is different from latency. Because GPUs prioritize bandwidth their memory controllers buffer requests and schedule them to reduce idle channel time. Multiple requests can be in-process concurrently; while one request is opening a row in a bank of one DRAM another can be transferring data and many others can be waiting. (Also 200 cycles at 1 GHz is only 200ns not 2µs.) The question deserve a real answer, but this is a quick hint.
– Paul A. Clayton
Jan 27 at 20:13
add a comment |
Bandwidth is different from latency. Because GPUs prioritize bandwidth their memory controllers buffer requests and schedule them to reduce idle channel time. Multiple requests can be in-process concurrently; while one request is opening a row in a bank of one DRAM another can be transferring data and many others can be waiting. (Also 200 cycles at 1 GHz is only 200ns not 2µs.) The question deserve a real answer, but this is a quick hint.
– Paul A. Clayton
Jan 27 at 20:13
Bandwidth is different from latency. Because GPUs prioritize bandwidth their memory controllers buffer requests and schedule them to reduce idle channel time. Multiple requests can be in-process concurrently; while one request is opening a row in a bank of one DRAM another can be transferring data and many others can be waiting. (Also 200 cycles at 1 GHz is only 200ns not 2µs.) The question deserve a real answer, but this is a quick hint.
– Paul A. Clayton
Jan 27 at 20:13
Bandwidth is different from latency. Because GPUs prioritize bandwidth their memory controllers buffer requests and schedule them to reduce idle channel time. Multiple requests can be in-process concurrently; while one request is opening a row in a bank of one DRAM another can be transferring data and many others can be waiting. (Also 200 cycles at 1 GHz is only 200ns not 2µs.) The question deserve a real answer, but this is a quick hint.
– Paul A. Clayton
Jan 27 at 20:13
add a comment |
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Bandwidth is different from latency. Because GPUs prioritize bandwidth their memory controllers buffer requests and schedule them to reduce idle channel time. Multiple requests can be in-process concurrently; while one request is opening a row in a bank of one DRAM another can be transferring data and many others can be waiting. (Also 200 cycles at 1 GHz is only 200ns not 2µs.) The question deserve a real answer, but this is a quick hint.
– Paul A. Clayton
Jan 27 at 20:13