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> If the rumor mill is to be believed, AMD’s incoming high-end graphics card could be a monster board bristling with 80 CUs (compute units) I thought modern GP
by hellofunk 7y ago
> If the rumor mill is to be believed, AMD’s incoming high-end graphics card could be a monster board bristling with 80 CUs (compute units)
I thought modern GPUs had hundreds of cores, or is a compute unit something different?
- imtringued 7y agoImagine you have a fleet of 64 buses each filled with 64 passengers. Does that count as 64 individual vehicles or as 4096?
- smcl 7y agoWell "vehicle" in this case is unambiguous - there's no confusion between a passenger and a vehicle in the scenario you described. For many there's not such a clear distinction between "cores" and "compute units" so I can see where the confusion arises.
- dragontamer 7y agoEach compute unit handles 2560 hardware threads (64 per clock tick per compute unit). AMDs GCN architecture runs 4 threads over 4 clock ticks natively. I forget if it was vertical SIMD or horizontal SIMD or whatever the proper terminology was. But this 4 threads over 4 clock ticks avoids the register stall issue. (RDNA performs 1 thread per clock tick and schedules around the stalls) The other threads come from an SMT-like / hyperthread-like feature, allowing 10 hardware threads per slot. All together, a compute unit supports 16 way SIMD per vALU x 4 vALUs per CU x 4 threads over 4 clock ticks x 10 'hyperthread-like' = 2560 hardware threads (over 4 clock ticks) 16 SIMD x 4 clock ticks gives your 64 sized wavefronts / warps that the programmer works with. The majority of the 'threads' are for latency hiding: work the GPU can do while waiting for RAM to respond. (In contrast to a CPU, which will search ~200 instructions out of order for work while waiting on RAM)