KR-20260068042-A - CXL Controller Apparatus and Method for Thermal Suppression by Reducing Light Source Emission Time Based on an Inline Compression Engine

KR20260068042AKR 20260068042 AKR20260068042 AKR 20260068042AKR-20260068042-A

Abstract

The present invention relates to a CXL controller device (10) connected to an external memory via an optical communication line based on the CXL protocol. The CXL controller device (10) includes a data analysis logic (400) that detects redundancy in source data, an inline compression engine (500) that performs hardware-level real-time lossless compression, and an optical transmission interface (600) that suppresses heat generation in the optical communication line (200) and surrounding circuits by shortening the light emission time and frequency of a light source (700) in proportion to the reduction in the total amount of compressed bits. The data analysis logic (400) includes a zero pattern detection unit (410), a compressibility determination unit (420), a heat grade classification unit (430), a compression ratio prediction unit (440), and a persistence detection unit (450), and the optical transmission interface (600) includes a current control unit (620), a non-light emission encoding unit (640), a bit distribution scheduler (660), a dual modulation control unit (670), and a WDM heat distribution unit (680). Laser heat generation in the AI inference environment is fundamentally suppressed by the voice feedback loop of the light source temperature feedback-based thermal control unit (810), the reinvestment of saved power into memory performance (910), and the in-chip thermal budget reallocation (930) function.

Inventors

안범주

Assignees

안범주

Dates

Publication Date: 20260513
Application Date: 20260426

Claims (15)

In a CXL (Compute Express Link) controller that controls data transfer between a processor and an external memory connected via an optical communication line, Data analysis logic that detects redundancy in data patterns by analyzing source data received from the above processor or the above external memory; An inline compression engine that reduces the total amount of data bits by compressing the source data in real-time at the hardware level based on the results of the above data analysis logic; and It includes an optical transmission interface that converts data compressed by the above-mentioned inline compression engine into an optical signal of the above-mentioned optical communication line and transmits it, A CXL controller device for low-power optical communication acceleration, characterized in that the optical transmission interface is configured to suppress heat generation in the optical communication line and surrounding circuits by shortening the light emission time or the number of light emission cycles of the light source in proportion to the reduction in the total amount of data bits.
A CXL controller device according to claim 1, wherein the data analysis logic includes a zero pattern detection unit that detects a zero pattern in which the entire cache line of the source data consists of zeros, and the optical transmission interface transmits data using a non-luminous encoding method that omits the light emission of the light source itself for the cache line detected as the zero pattern and interprets a light non-luminous section of a predetermined length as the transmission of zero data to the receiving side, thereby completely blocking laser heat generation during the corresponding cache line transmission section.
A CXL controller device according to claim 1, wherein the optical transmission interface comprises: a compression ratio receiver that receives a compression ratio calculated by the inline compression engine in cache line units; and a current controller that dynamically controls a laser emission duty cycle to reduce the laser driving current inversely proportional to the compression ratio, such that when the compression ratio is 2:1, the laser emits light for only 50% of the original transmission time, and when the compression ratio is 4:1, the laser emits light for only 25% of the original transmission time.
The CXL controller device according to claim 1 further comprises: a thermal sensing unit for measuring the current temperature of a light source or peripheral circuit of the optical transmission interface; and a thermal control unit for automatically increasing the compression level of the inline compression engine to increase the compression ratio when the current temperature exceeds a predetermined thermal threshold, thereby further shortening the light emission time, and returning the compression level to a standard when the current temperature drops below a predetermined cooling return level.
A CXL controller device according to claim 1, wherein the CXL controller device further comprises a distance-linked compression target setting unit that sets a higher minimum target compression ratio to the inline compression engine as the round-trip delay time is greater, by referring to the optical signal round-trip delay time between the processor and the external memory measured through the optical communication line.
A CXL controller device according to claim 1, wherein the optical communication line supports a wavelength division multiplexing method, and the optical transmission interface includes a WDM heat dissipation unit that distributes the thermal load per channel such that data with a high compression ratio is placed in a first wavelength channel and data with a low compression ratio is placed in a second wavelength channel, wherein the laser source of the first wavelength channel operates at a low temperature with a short emission time and the laser source of the second wavelength channel operates with a normal emission time.
A CXL controller device according to claim 1, wherein the data analysis logic includes a compression ratio prediction unit that learns past memory access patterns and compression ratio history to pre-calculate an expected compression ratio of a currently requested memory address range, and the optical transmission interface includes a predictive laser pre-cooling unit that pre-reduces the laser driving current to a pre-cooling level before actual data transmission starts when the expected compression ratio is above a predetermined threshold.
A CXL controller device according to claim 1, wherein the data analysis logic includes a compression possibility determination unit that determines compression failure when the compression ratio is less than a predetermined minimum threshold, and the optical transmission interface includes a split transmission unit that divides the data determined to be compression failure into sub-chunks of a predetermined size and inserts a minimum light emission pause interval between each sub-chunk to disperse heat concentration caused by continuous light emission.
The CXL controller device according to claim 1 further comprises: a power saving calculation unit that calculates in real time the amount of laser power consumed by the reduction of the light emission time; and a power reinvestment control unit that reinvests the saved power into increasing the DDR channel operating frequency of the external memory or optimizing the memory refresh interval.
A CXL controller device according to claim 1, wherein the optical transmission interface includes a bit distribution scheduler that reduces peak current stress of a laser diode and extends the lifespan of a laser element by reducing the maximum optical signal intensity per unit time through the reduction of the maximum optical signal intensity by evenly distributing the bits reduced by compression over the entire transmission frame period when transmitting the compressed data to an optical communication line.
A CXL controller device according to claim 1, wherein the data analysis logic includes a thermal class classification unit that classifies received source data into three grades—high compression grade, medium compression grade, and low compression grade—according to the expected compression ratio, and the optical transmission interface preloads a laser control profile corresponding to each grade before compression is completed.
A method for suppressing heat generation of a light source during data transmission between a processor and an external memory connected via an optical communication line, (a) A step in which the data analysis logic of the CXL controller detects redundancy patterns in the source data; (b) A step in which an inline compression engine reduces the total amount of data bits by compressing the source data in real-time losslessly at the hardware level; (c) a step in which an optical transmission interface converts the compressed data into an optical signal and transmits it to an optical communication line, wherein the emission time or number of emission cycles of a light source is shortened in proportion to the reduction amount of the total bit amount; and (d) A CXL data transmission method for low-power optical communication acceleration, comprising the step of calculating the laser power consumption reduced by shortening the emission time and frequency, and optimizing the operation parameters of the external memory based on the above.
A CXL controller device according to claim 1, wherein the optical transmission interface comprises a dual modulation control unit that performs dual modulation by adjusting the laser output power in steps according to the compression ratio calculated by the inline compression engine, in addition to OOK (On-Off Keying) data modulation, to 75% of the standard when the compression ratio is 2:1, 50% when the compression ratio is 3:1, and 25% when the compression ratio is 4:1 or higher, wherein the optical receiver on the receiving side measures the strength of the received optical signal, inversely calculates the compression ratio, and automatically sets the decoding parameters.
A CXL controller device according to claim 1, wherein the data analysis logic includes a persistence detection unit that detects compression pattern persistence in which the same or similar compression pattern is repeated more than a predetermined number of times in a plurality of consecutive cache lines, and the optical transmission interface switches to a planned cooling mode that gradually reduces the laser driving current to lower the temperature of the light source to a target cooling level when the compression pattern persistence is detected, and returns to a standard mode when the pattern changes.
The CXL controller device according to claim 1 further comprises: a heat reduction calculation unit that calculates in real time the amount of heat generated by the light source reduced by the reduction of the light emission time; a circuit heat monitoring unit that monitors the current heat generation status of the electrical circuit blocks within the CXL controller device; and a heat budget redistribution control unit that transfers the amount of heat generated by the reduced light source to the heat budget of the electrical circuit block including the inline compression engine to allow the circuit block to operate at a higher clock frequency, provided that the total amount of heat generated by the entire CXL controller device does not exceed a predetermined thermal design power limit.

Description

CXL Controller Apparatus and Method for Thermal Suppression by Reducing Light Source Emission Time Based on an Inline Compression Engine The present invention relates to the field of semiconductor memory interconnects and optical communication technology, and more specifically, to a CXL controller device and method for controlling data transmission between a processor supporting the CXL (Compute Express Link) protocol and an external memory connected via an optical communication line, wherein the source data is compressed losslessly in real-time at the hardware level to reduce the total amount of bits, and the emission time or number of emission cycles of a laser source is shortened in proportion to the reduction in the total amount of bits, thereby suppressing heat generation in the optical communication line and surrounding circuits. As the computational density of AI accelerators increases rapidly, there is a growing technical demand to perform more computations and access more memory within the Thermal Design Power (TDP) limits of a single chip. In particular, in large-scale language model (LLM) inference environments processing hundreds of billions of parameters, frequent high-speed memory access to model weights and Key-Value Cache (KV-Cache) data is required. To meet this need, Memory Disaggregation architectures, which connect processors such as GPUs and CPUs with large-capacity external memory via high-speed interconnects, are emerging as a core technology for data centers. The CXL (Compute Express Link) standard is an open interconnect specification that standardizes this memory separation architecture, providing cache-coherent memory semantics by defining the CXL.cache and CXL.mem subprotocols on top of the PCIe (PCI Express) physical layer. Memory pooling via CXL switches has been supported since CXL 2.0, and hardware-level memory sharing has been standardized in CXL 3.0. Furthermore, optical communication CXL technology, which applies optical communication lines to CXL connections to extend the transmission distance of CXL to tens of meters or several kilometers, is entering the commercialization stage through Lightelligence's Photowave (2023), Samtec's fiber-optic-based CXL PoC, and MACOM's PCIe/CXL optical communication expansion chipset (2025). The laser source, a core component of optical line-based CXL (hereinafter referred to as 'Optical Communication CXL'), is the key light-emitting element of the optical transmitter that converts electrical signals into optical signals. The laser source emits light while continuously receiving an electric current during data transmission, and significant heat is generated during this process due to limitations in electrical-to-optical conversion efficiency. The heat generated by the laser diode raises the temperature of the semiconductor junction, leading to wavelength fluctuations, reduced output power, decreased reliability, and shortened lifespan. For optical transceivers and CXL optical communication controllers deployed on a large scale in data centers, the accumulated heat from the laser source is the cause of major thermal density issues. In particular, as the TDP of AI accelerators tends to exceed 1 kW, laser heat generated by adjacent optical transceivers complicates overall system thermal management. Conventional laser thermal management technologies have utilized passive and active cooling means such as thermo-electric coolers (TECs), thermal conductive sheets, heat dissipation fins, and cooling fans. However, these passive thermal management methods require additional component costs and installation space, and fail to address the root cause of heat generation. Although dynamic power gating technology for laser sources has been proposed, this method turns off the laser only during idle periods when there is no data transmission; consequently, during actual data transmission, the laser consumes the entire power and heat generation persists. Meanwhile, technology for integrating inline compression functions into CXL controllers is being developed. The Open Compute Project (OCP) Hyperscale CXL Classification Memory Expander specification defines hardware-accelerated lossless compression at the cache line level, and the Marvell Structera A CXL controller is equipped with LZ4 inline compression/decoding capabilities. However, while such inline compression technologies were developed to increase memory capacity and improve bandwidth efficiency, the concept of suppressing heat generation by directly linking the reduction in total bit volume through compression to a reduction in the emission time or frequency of a light source is not disclosed in any prior art. In other words, the technical concept of linking data compression with laser thermal management is currently unknown, and this invention proposes that the combination of these two technologies represents a novel approach that fundamentally resolves the thermal problems of optical communicatio