Pascal (microarchitecture)


Pascal is the codename for a GPU microarchitecture developed by Nvidia, as the successor to the Maxwell architecture. The architecture was first introduced in April 2016 with the release of the Tesla P100 on April 5, 2016, and is primarily used in the GeForce 10 series, starting with the GeForce GTX 1080 and GTX 1070, which were released on May 17, 2016 and June 10, 2016 respectively. Pascal was manufactured using TSMC's 16nm FinFET process, and later Samsung's 14nm FinFET process.
The architecture is named after the 17th century French mathematician and physicist, Blaise Pascal.
On March 18, 2019, Nvidia announced that in a driver due for April 2019, they would enable DirectX Raytracing on Pascal-based cards starting with the GTX 1060 6 GB, and in the 16 series cards, a feature reserved to the Turing-based RTX series up to that point.

Details

In March 2014, Nvidia announced that the successor to Maxwell would be the Pascal microarchitecture; announced on May 6, 2016 and released on May 27 of the same year. The Tesla P100 has a different version of the Pascal architecture compared to the GTX GPUs. The shader units in GP104 have a Maxwell-like design.
Architectural improvements of the GP100 architecture include the following:
Architectural improvements of the GP104 architecture include the following:

Graphics Processor Cluster

A chip is partitioned into Graphics Processor Clusters. For the GP104 chips, a GPC encompasses 5 SMs.

Streaming Multiprocessor "Pascal"

A "Streaming Multiprocessor" corresponds to AMD's Compute Unit. An SMP encompasses 128 single-precision ALUs on GP104 chips and 64 single-precision ALUs on GP100 chips.
What AMD calls a CU can be compared to what Nvidia calls an SM. While all CU versions consist of 64 shader processors, Nvidia experimented with very different numbers:
The Polymorph Engine version 4.0 is the unit responsible for Tessellation. It corresponds functionally with AMD's Geometric Processor. It has been moved from the shader module to the TPC to allow one Polymorph engine to feed multiple SMs within the TPC.

Chips

On the GP104 chip an SM consists of 128 single-precision ALUs, on the GP100 of 64 single-precision ALUs. Due to different organization of the chips, like number of double precision ALUs, the theoretical double precision performance of the GP100 is half of the theoretical one for single precision; the ratio is 1/32 for the GP104 chip.
GK104GK110GM204 GM204 GM200GP104GP100
Dedicated texture cache per SM48 KiB
Texture or read-only data cache per SM48 KiB
Programmer-selectable shared memory/L1 partitions per SM48 KiB shared memory + 16 KiB L1 cache 48 KiB shared memory + 16 KiB L1 cache rowspan="3" rowspan="3" rowspan="3" rowspan="3" rowspan="3"
Programmer-selectable shared memory/L1 partitions per SM32 KiB shared memory + 32 KiB L1 cache32 KiB shared memory + 32 KiB L1 cache-----
Programmer-selectable shared memory/L1 partitions per SM16 KiB shared memory + 48 KiB L1 cache16 KiB shared memory + 48 KiB L1 cache-----
Unified L1 cache/texture cache per SM48 KiB48 KiB48 KiB48 KiB24 KiB
Dedicated shared memory per SM96 KiB96 KiB96 KiB96 KiB64 KiB
L2 cache per chip512 KiB1536 KiB1792 KiB2048 KiB3072 KiB2048 KiB4096 KiB

Performance

The theoretical single-precision processing power of a Pascal GPU in GFLOPS is computed as 2 X × number of CUDA cores × core clock speed.
The theoretical double-precision processing power of a Pascal GPU is 1/2 of the single precision performance on Nvidia GP100, and 1/32 of Nvidia GP102, GP104, GP106, GP107 & GP108.
The theoretical half-precision processing power of a Pascal GPU is 2× of the single precision performance on GP100 and 1/64 on GP104, GP106, GP107 & GP108.

Successor

The Pascal architecture was succeeded in 2017 by Volta in the HPC, cloud computing, and self-driving car markets, and in 2018 by Turing in the consumer and business market.