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An era of history ended as Intel decided to discontinue processors using the Itanium instruction set. Itanium was a new CPU architecture family, it was incompatible with the well know x86 or ARM instruction set. The CPU struggled on the market for almost two decades to gain market share. The project is one of the biggest fiasco of the processor history and Intel.
The Itanium CPU was originally designed by HP. The goal of HP was to create a server and mainframe CPU. The new conception of the CPU was to have a very complex instruction set, where one instruction can do a lot of calculations. This conception is called VLIW (very long instruction word). Later, HP and Intel joined their forces to design and manufacture the CPU.
How the CPU-s usually worked
CPU-s are usually RISC or CISC. The goal of RISC instruction set is to create CPU-s with small and simple instructions. Notable example of RISC CPU-s are the ARM instruction set (such as the CPU in your mobile phone) and MIPS instruction set (usually used in smart TV-s, older tablets, and routers). Another well-known family is the CISC: this means complex instruction set. An example for CISC is the x86 instruction set, which is currently used in desktop computers and laptops (usually on the Windows based machines). A CISC based design is more complex, an instruction on a CISC cpu can usually do memory read and write, array indexing, stack displacement, and a logical operation within one instruction. The instruction length is different each time. In modern CISC CPU-s, the instructions are decoded to RISC instructions, therefore, our current x86 CPU-s are internally RISC CPU-s, running a hardware accelerated x86 code decoder.
The Itanium and the VLIW architecture
The Itanium follows a new idea: the VLIW is more complex than ARM and even more complex than CISC. On Itanium, an instruction is being created from sub-instructions. On the traditional CISC and RISC CPU-s, we having more execution pipelines in every core. This allows each CPU core to execute code parallelly. (Do not confuse this with multi-core CPU-s, thats different!). The CPU have to detect independent operations to be able to execute instructions within one clock cycle. To spare some logic circuits, in the Itanium they came up with a new idea. On Itanium, they rely on the compiler to detect and flag these independent instructions.
The Itanium and the compilers
The compiler has more extra things to do than just that. They also rely on the compiler to re-organize these instructions to reach the best performance. The compiler will have to be able to fill these large instructions with sub-instructions very efficiently, to be able to create code with good performance. The Itanium architecture is, however, overcomplicated, the documentation is too long, and its hard to understand it. So the compiler writers were unable to create very efficient compilers.
The first Itanium-based implementations
Intel and HP was very pretentious with the new architecture. They was able to onboard other corporations as well. First they have planned to release the architecture on the server and mainframe market. Then they planned to release the new platform for the high-end PC market. The Itanium was released in 2001 summer.
The first Itanium CPU was the Merced CPU core. It was very weak, even a regular desktop Pentium4 or AMD Athlon was able to outperform it under the most tasks. This resulted a high dissatisfication among the buyers. The market didnt liked the new solution, and the server market was choosing x86 based CPU-s. The first Itanium processors had a built in x86 processors to be able to run the traditional x86 code. However, this built in CPU was too slow, they have later removed it, and added a software-only emulator.
Intel updates the Itanium line
Intel have tried to fix the performance with the new, second generation of Itanium CPU. However, AMD was released the first 64 bit x86 processor, called the AMD Athlon64. The Athlon64 implemented a new, 64 bit variation of x86 called x86-64 (AMD64) and pushed the x86 family into the servers. The first 64 bit x86 CPU-s only had 100 million transistors, they was available for a couple 100 dollars. In comparison, the second generation of Itanium CPU had almost 250 million transistors, and the cost was varying bethwen 1000 and 3000 us dollars. The power consumption of the Itanium was either similar or worse than the x86 counterparts.
Intel and HP is not able to convience users
The compilers are not getting much more efficient. Programmers usually dont bother releasing software to Itanium. Combined with high cost, low relative performance, the support quickly melts beyond Itanium. Intel and HP expected 40 billion USD revenue from selling Itanium servers. The forecast became worse and worse every year.
Every vendor discontinued selling Itanium based solutions after a few months, except HP. The high-end desktop Itanium models never materialized. The market was grinded down by the regular x86-64 based computers.
Intel updates the Itanium
Intel updated the Itanium line, they have created new multicore models. They have redesigned Itanium to use the newer manufacturing lines serveral times. The last Itanium processor was released in 2017, it had 8 to 16 cores, and was manufactured on 32nm process. Despite of the frequent updates, Intel and HP failed to sell big quantity of Itanium based hardware. HP had to sue other corporations which has discontinued to supply software for the Itanium architecture due to low demand, despite of having contract for it. Despite of lawsuits, the architecture lost all the software company behind it.
Windows and Linux discontinued supporting Itanium
Yesterday (2020 januar 22.), Microsoft stopped releasing new updates for Windows Server 2008 for the Itanium architecture. Red Had Linux discontinued every Itanium related development, but they will continue to offer limited support for the existing operating system until 2024. Debian Linux have already discontinued supporting Itanium in 2018. Suse will support debian up to 2022, but they will not release any new operating system for it.
Intel discontinued selling Itanium
Intel will accept new orders for Itanium for 3 more work-days. After that date, Intel will not ship more Itanium CPU-s. They will continue to offer warranty service until 2021 summer, when they close down all the remaining Itanium-related infrastructure and facility.