PantheonSim / GPUs / NVIDIA A40

Simulated NVIDIA A40: a GPU profile for CUDA and ROCm testing

PantheonSim, the GPU simulator for CUDA and ROCm, simulates the NVIDIA A40 (Ampere, 8.6) as the profile nvidia/a40. A 48 GB Ampere GPU for data-center visual computing and AI. Its profile is built from public documents and not yet measured against a physical card.

The profile at a glance

These are the numbers a program can ask this simulated GPU, and the values nvidia-smi show for it. They come from the profile file in the simulator's repository, pinned to one commit of it.

Property	Value
Profile id	`nvidia/a40`
Vendor and architecture	NVIDIA, Ampere
Compute capability	`8.6`
Device memory	48.0 GiB, GDDR
Streaming multiprocessors	84
Warp size	32
Max threads per multiprocessor	1536
Shared memory per block (opt-in maximum)	99 KiB
L2 cache	6 MiB
Memory bus width	384-bit
Power limit (profile)	300 W
Maximum clocks (profile)	1740 MHz shader, 7250 MHz memory
ECC memory	yes
PCIe link reported	Gen4 x16
Tensor or matrix cores	yes
Verified (measured on a physical card)	not yet measured

What this GPU is for

A 48 GB Ampere GPU for data-center visual computing and AI.

Ampere covers two compute capabilities in these profiles: 8.0 for the GA100 data-center parts and 8.6 for the GA10x parts. The simulator runs the SASS a binary carries for the architecture and falls back to PTX when it carries none.

Among the 37 NVIDIA profiles it ranks 18th by device memory (48.0 GiB) and 22nd by SMs (84), counting the largest as first.

Is this profile verified?

No. This profile is marked not verified: it is built from public documents only, and nothing in it was measured on a physical card. Some figures are derived or copied from the nearest profile where the vendor publishes none, so treat them as approximate, and memory sizes as upper bounds. Programs still run on it, and it still answers every call as the architecture's rules require, but a value such as a clock or a limit may differ from a real card's.

Simulate this GPU

Build the simulator (see the docs) or open the playground, then:

nvcc -cudart shared -arch=compute_86 my_app.cu -o my_app
vgpu run --gpu nvidia/a40 ./my_app
vgpu shell -y --gpu nvidia/a40 --count 4
vgpu info --gpu nvidia/a40

This profile is compute capability 8.6. A kernel built for compute_75 runs on it and on every other NVIDIA profile; a kernel built for a newer architecture is refused by a profile that is older than it. Link the CUDA runtime shared (-cudart shared) so the simulator can stand in for it.

To use it every time, put gpu: nvidia/a40 in a pantheonsim.yaml settings file, or in a GitHub Actions job give the PantheonSim action gpu: nvidia/a40 (see CUDA and HIP tests in GitHub Actions). The simulator checks behaviour and has no timing model, so a run on a physical GPU before a release still counts. The CUDA guide explains the rest.

Where the numbers come from

Each profile file begins with a note on its sources. This is the note for NVIDIA A40, as written in the file:

Source note for nvidia/a40

Public values; verified: false, nothing here has been measured on a card. Where each value comes from: - compute capability 8.6: NVIDIA's CUDA GPUs table (developer.nvidia.com/cuda-gpus). - SMs 84: NVIDIA Ampere GA102 GPU Architecture whitepaper (v2), Table 3 (A40: 84 SMs, 10752 CUDA Cores at 128 an SM, 336 Tensor Cores), and the A40 data sheet's "10,752 CUDA cores". - memory 48 GB GDDR6 with ECC, 696 GB/s, 300 W, PCIe Gen4: the A40 data sheet. The whitepaper's table gives the frame buffer as 49152 MB, 14.5 Gbps, and a 1740 MHz boost clock. NVIDIA's "GB" for graphics memory is binary (see rtx2080ti.yaml), so vram_bytes is 49152 MiB; a real card's nvidia-smi total is a little smaller, so this is an upper bound. - PCI device 0x2235, "NVIDIA A40", from the name table in NVIDIA's open GPU kernel modules (g_nv_name_released.h). - Per-SM limits are compute capability 8.6's, the same as nvidia/a10 and nvidia/rtx3080ti, which were read from physical cards. - The optional NVLink bridge (112.5 GB/s) is not recorded, as for nvidia/h100-pcie. - CUDA attributes (the `cuda:` section and l2_cache_bytes): L2 6144 KB and the 384-bit bus: GA102 whitepaper; persisting L2 copied from nvidia/a10.

The GPU index lists every profile, and this one is not yet measured.

Other Ampere profiles: