High Bandwidth Memory

Excessive Bandwidth Memory (HBM) is a computer memory interface for 3D-stacked synchronous dynamic random-access memory (SDRAM) initially from Samsung, AMD and SK Hynix. RAM in upcoming CPUs, and FPGAs and in some supercomputers (such as the NEC SX-Aurora TSUBASA and Fujitsu A64FX). HBM achieves increased bandwidth than DDR4 or GDDR5 while utilizing much less power, and in a substantially smaller type issue. That is achieved by stacking up to eight DRAM dies and an optionally available base die which may embody buffer circuitry and take a look at logic. The stack is often linked to the memory controller on a GPU or CPU via a substrate, equivalent to a silicon interposer. Alternatively, the memory die may very well be stacked immediately on the CPU or GPU chip. Inside the stack the dies are vertically interconnected by via-silicon vias (TSVs) and microbumps. The HBM know-how is analogous in precept but incompatible with the Hybrid Memory Cube (HMC) interface developed by Micron Expertise. HBM Memory Wave Routine bus is very extensive in comparison to different DRAM memories equivalent to DDR4 or GDDR5.



An HBM stack of 4 DRAM dies (4-Hello) has two 128-bit channels per die for a total of 8 channels and a width of 1024 bits in total. A graphics card/GPU with four 4-Hi HBM stacks would subsequently have a memory bus with a width of 4096 bits. As compared, the bus width of GDDR memories is 32 bits, with 16 channels for a graphics card with a 512-bit memory interface. HBM helps as much as 4 GB per package. The bigger number of connections to the memory, relative to DDR4 or GDDR5, required a new technique of connecting the HBM memory to the GPU (or Memory Wave different processor). AMD and Nvidia have both used purpose-constructed silicon chips, referred to as interposers, to connect the memory and GPU. This interposer has the added advantage of requiring the memory and processor to be bodily close, reducing memory paths. Nonetheless, as semiconductor system fabrication is considerably dearer than printed circuit board manufacture, this adds price to the final product.



The HBM DRAM is tightly coupled to the host compute die with a distributed interface. The interface is divided into unbiased channels. The channels are fully independent of one another and will not be essentially synchronous to each other. The HBM DRAM uses a wide-interface structure to attain high-speed, low-power operation. Each channel interface maintains a 128-bit information bus working at double data charge (DDR). HBM helps switch charges of 1 GT/s per pin (transferring 1 bit), yielding an total package bandwidth of 128 GB/s. The second era of Excessive Bandwidth Memory, HBM2, additionally specifies up to eight dies per stack and doubles pin switch charges as much as 2 GT/s. Retaining 1024-bit broad entry, HBM2 is in a position to reach 256 GB/s memory bandwidth per package. The HBM2 spec permits up to eight GB per package deal. HBM2 is predicted to be especially useful for efficiency-sensitive client purposes comparable to virtual reality. On January 19, 2016, Samsung introduced early mass manufacturing of HBM2, at up to eight GB per stack.



In late 2018, JEDEC announced an replace to the HBM2 specification, providing for increased bandwidth and capacities. As much as 307 GB/s per stack (2.5 Tbit/s efficient knowledge rate) is now supported within the official specification, though merchandise working at this pace had already been out there. Additionally, the update added support for 12-Hello stacks (12 dies) making capacities of up to 24 GB per stack doable. On March 20, 2019, Samsung announced their Flashbolt HBM2E, featuring eight dies per stack, a transfer price of 3.2 GT/s, providing a total of sixteen GB and 410 GB/s per stack. August 12, 2019, SK Hynix announced their HBM2E, featuring eight dies per stack, a transfer fee of 3.6 GT/s, offering a total of sixteen GB and 460 GB/s per stack. On July 2, 2020, SK Hynix introduced that mass manufacturing has begun. In October 2019, Samsung introduced their 12-layered HBM2E. In late 2020, Micron unveiled that the HBM2E customary would be updated and alongside that they unveiled the subsequent standard often called HBMnext (later renamed to HBM3).