So long, Itanium

I have mixed feelings about Intel announcing the end of Itanic the Itanium. Everyone knew this was coming, of course, but Intel finally officially gave Itanium a death date of mid-2021 instead of keeping it limping along as it has for the past several years.

On the one hand, I don't like Itanium for killing PA-RISC. The first machine I ever had root on was a HP K250 running HP-UX 10.20, and I still have a PA-RISC laptop (an RDI PrecisionBook C160L) and a C8000 with dual PA-8900s, the most powerful Precision Architecture workstation HP ever made. I thought PA-RISC was a nice, clean instruction set with decent performance and HP seemed to at least try to keep up with PowerPC and SPARC, and I think it died before its time (there was even talk of using PA-RISC in Amiga computers!). HP is still the Itanium's only customer, mostly because they would probably roil the remnant HP-UX user base with another architecture switch. In fairness, it should be noted that it was HP themselves that didn't think there was any money in continuing with developing their own CPU (the same logic they applied to killing the DEC Alpha, another exceptional architecture murdered way too early), and that may have been true at the time, but Itanium has painted the Superdomes into a corner and HP-UX and OpenVMS will probably go the way of emulation like the Unisys mainframes have gone.

On the other hand, the end of IA-64 marks the end of an era, not only for non-x86 designs within Intel, but as the last major VLIW CPU (which Intel and HP called "EPIC"). GPUs are of course largely VLIW, VLIW chips still turn up in embedded systems applications and there are still oddballs like the Russian Elbrus, but as a CPU architecture load/store designs have largely won. Even your typical Intel chip is essentially a modern RISC-style core with an x86_64 instruction decoder bolted on (and of course all that other black box crap that you don't get with POWER9). Itanium made it worse with a pretty weaksauce x86 emulator and its unusual architecture choices that make it relatively resistant to Spectre-style attacks but difficult to optimize typical software applications for, a recurrent problem with VLIW compilers in general. This was one of the big reasons the SGI IA-64 workstations never really took off compared to the MIPS systems they replaced.

Big classic proprietary CPUs were a big part of my early career and losing Itanium is a sad whimper. But while Power ISA is a much less adventurous design, it's a much more performant one, and OpenPOWER means it will stay relevant for a long time to come. If you've got a Talos II under your desktop as I do, you chose right.


  1. I had no idea the Itanium was at all still going, this hit me as quite the surprise. The server world really is a completely different beast compared to our everyday, casual desktop world. Kinda makes me wish I had more access to server class hardware in general, regardless of architecture. You had a cool career kickstart, Mr. Kaiser!

    One day, I hope to be able to afford an OpenPOWER system. And I hope A LOT MORE that, by then, QEMU (or better yet, HQEMU) will already be able to run OS 9, Tiger and Leopard in virtualization mode instead of emulation mode. A MAN CAN DREAM! lol

  2. IPF wasn't VLIW, and it didn't "kill" PA; HP had designed it from day one as the incompatible next generation of PA.

    I'd also disagree with the assertion that there aren't many, many, many other VLIW CPU cores. Hexagon sells by the tens of millions. There's also SHARC, C6000, the higher-end Tensilica and Ceva products, etc. For putting lots of ALUs in a low power profile, VLIW is still king and likely will be indefinitely.

    (Also, GPUs haven't been VLIW, for the most part, in a long time. AMD switched away from that with GCN.)

  3. Point well taken on the other cores, but I'll simply say I politely dispute your other assertions in the interest of not starting a delayed argument.


Post a Comment

Comments are subject to moderation. Be nice.