Editing intel/loihi 2

{{intel title|Loihi 2}}
{{chip
|chip type=neuromorphic chip
|name=Loihi 2
|image=File:intel loihi 2 chip.png
|designer=Intel
|manufacturer=Intel
|market=Artificial Intelligence
|first announced=September 30, 2021
|first launched=September 30, 2021
|process=Intel 4
|transistors=2,300,000,000
|technology=CMOS
|die area=31 mm²
|max cpus=16,384
|v core min=0.50 V
|v core max=1.25 V
|predecessor=Loihi
|predecessor link=intel/loihi
|neuron count=1,000,000
|synapse count=120,000,000
}}
'''Loihi 2''' (pronounced low-ee-hee 2) is the successor to {{\\|Loihi}}, a second-generation neuromorphic research test chip designed by Intel Labs that was introduced in late 2021. The chip uses an asynchronous spiking neural network (SNN) to implement adaptive self-modifying event-driven fine-grained parallel computations used to implement learning and inference with high efficiency. The chip is a 128-neuromorphic cores many-core IC fabricated on [[Intel 4]] process and features a unique programmable microcode learning engine for on-chip SNN training.

== Overview ==
Introduced in September 2021, Loihi 2 is the successor to {{\\|Loihi}}, a neuromorphic research test chip. Like its predecessor, {{\\|Loihi}}, Loihi 2 consists of an asynchronous spiking neural network (SNN) meaning instead of manipulating signals, the chip sends spikes along activate synapses. Connections are asynchronous and highly timed-based. Neuromorphic cores containing many neurons are interlinked and receive spikes from elsewhere in the network. When received spikes accumulate for a certain period of time and reach a set threshold, the core will fire off its own spikes to its connected neurons. Preceding spikes reinforce each other and the neuron connections while spikes that follow will inhibit the connection, declining the connectivity until all activities are halted.

Loihi 2 is fabricated on pre-production [[Intel 4 process]] and has a total of 1,000,000 artificial neurons and 120 million synapses. In addition to the 128 neuromorphic cores, there are 6 managing Lakemont cores.

=== Key changes from {{\\|Loihi}} ===
* [[Intel 14 nm]] -> [[Intel 4 process]]
* 1.10x transistors
* 0.9x synapse (120,000,000, down from 130,000,000)
* 7.7x neurons (1,000,000, up from 130,000)
** 8192 neurons/0.21 mm² Core (up from 1024 neurons/0.41 mm² Core)
* 2x microprocessor count (6, up from 3)
* 3D mesh scaling (from 2D)
* 32-bit integer payload (from binary)
* Rich programmable neuron cores
* 3-factor learning
* Faster circuits
* new interfaces
** gigabit ethernet

== Architecture ==
{{empty section}}

== Loihi 2-based neuromorphic system ==
Intel developed a series of systems based on Loihi 2 which scale to a large number of Neurons and Synapses.

{| class="wikitable"
|-
! Oheo Gulch !! Kapoho Point
|-
| PCIe card || 4" x 4" Ethernet
|-
| 1 Chip || 8 Chips
|-
| 120,000,000 Synapses || 960,000,000 Synapses
|-
| 1,000,000 Neurons || 8,000,000 Neurons
|}

=== Oheo Gulch (1 chip, 1M neurons) ===
'''Oheo Gulch''' is a PCIe card form factor that incorporates a single socketed Loihi 2 chip.

[[File:intel Oheo Gulch card.jpg|800px]]

=== Kapoho Point (8 chip, 8M neurons) ===
'''Kapoho Point''' a 4-inch by 4-inch form factor board featuring eight Loihi 2 chips arranged in a 2-stacked (double-sided PCB) 4x4 chips. With eight Loihi 2 chips, Kapoho Point incorporates 1,024 neuromorphic cores with 960,000 synapses and 8 million neurons.

[[File:intel Kapoho Point board.jpg|600px]]

== Die ==
* [[Intel 4 process]]
* 2,300,000,000 transistors
**  128 neuromorphic cores + 6 x86 cores
* 31 mm² die size
** Core area 0.21 mm²


: [[File:intel loihi 2 die shot.png|class=wikichip_ogimage|850px]]


: [[File:loihi 2 die (annotated).png|850px]]


<gallery widths=400px heights=400px>
File:Intel Loihi 2 Die.jpg
File:Intel Loihi 2 Fingertip.jpg
</gallery>

== Bibliography ==
* ''Some information was obtained directly from Intel''

== See also ==
* {{intel|Loihi}}
* {{ibm|TrueNorth}}
core voltage (max)	1.25 V (12.5 dV, 125 cV, 1,250 mV) +
core voltage (min)	0.5 V (5 dV, 50 cV, 500 mV) +
designer	Intel +
die area	31 mm² (0.0481 in², 0.31 cm², 31,000,000 µm²) +
first announced	September 30, 2021 +
first launched	September 30, 2021 +
full page name	intel/loihi 2 +
instance of	neuromorphic chip +
ldate	September 30, 2021 +
main image	+
manufacturer	Intel +
market segment	Artificial Intelligence +
max cpu count	16,384 +
name	Loihi 2 +
neuron count	1,048,576 +
smp max ways	16,384 +
synapse count	120,000,000 +
technology	CMOS +
transistor count	2,300,000,000 +