The AI Engine array interface consists of the PL and NoC interface tiles. The AI Engine array interface tiles manage the two following high performance interfaces.
- AI Engine to PL
- AI Engine to NoC
The following image shows the AI Engine array interface structure.
One AI Engine to PL interface tile contains eight streams from the PL to the AI Engine and six streams from the AI Engine to the PL. The following table shows one AI Engine to PL interface tile capacity.
|Number of Connections
|Data Width (bits)
|Bandwidth per Connection (GB/s)
|Aggregate Bandwidth (GB/s)
|PL to AI Engine array interface
|AI Engine array interface to PL
The exact number of PL and NoC interface tiles is device-specific. For example, in the VC1902 device, there are 50 columns of AI Engine array interface tiles. However, only 39 array interface tiles are available to the PL interface. Therefore, the aggregate bandwidth for the PL interface is approximately:
- 24 GB/s * 39 = 0.936 TB/s from AI Engine to PL
- 32 GB/s * 39 =1.248 TB/s from PL to AI Engine
The number of array interface tiles available to the PL interface and total bandwidth of the AI Engine to PL interface for other devices and across different speed grades is specified in Versal AI Core Series Data Sheet: DC and AC Switching Characteristics (DS957).
output_gmio attribute uses DMA in the AI Engine to NoC interface tile. The DMA has two
32-bit incoming streams from the AI Engine and
two 32-bit streams to the AI Engine. In
addition, it has one 128-bit memory mapped AXI master interface to the NoC NMU. The
performance of one AI Engine to NoC interface
tile is shown in the following table.
|Number of connections
|Bandwidth per connection (GB/s)
|Aggregate Bandwidth (GB/s)
|AI Engine to DMA
|DMA to NoC
|DMA to AI Engine
|NoC to DMA
The exact number of AI Engine to NoC interface tiles is device-specific. For example, in the VC1902 device, there are 16 AI Engine to NoC interface tiles. So, the aggregate bandwidth for the NoC interface is approximately:
- 8 GB/s * 16 = 128 GB/s from AI Engine to PL
- 8 GB/s * 16 = 128 GB/s from PL to AI Engine
When accessing DDR memory, the integrated DDR memory controller (DDRMC) number in the platform limits the performance of DDR memory read and write. For example, if all four DDRMCs in a VC1902 device are fully used, the hard limit to access DDR memory is as follows.
- 3200 Mb/s * 64 bit * 4 DDRMCs / 8 = 102.4 GB/s
The performance of
output_gmio accessing DDR
memory through the NoC is further restricted by the NoC lane number in the
horizontal and vertical NoC, inter-NoC configurations, and QoS. Note that DDR memory
read and write efficiency is largely affected by the access pattern and other
overheads. For more information about the NoC, memory controller use, and
performance numbers, see the
Versal Adaptive SoC Programmable Network on Chip and
Integrated Memory Controller LogiCORE IP Product Guide (PG313).
For a single connection from the AI Engine or to the AI Engine,
output_gmio have a hard bandwidth limit of 4 GB/s.
Some advantages and disadvantages for choosing
output_gmio are shown in the following table.