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Windows XP 2002 for the Itanium: Unbridled rage
- mghackerlady 2mo agoI miss itanium. I feel like a madman for saying it, but I do. Something about it is just alluring to me. Alas, the problems were too hard to solve or weren't worth solving anymore Ironically, it died around the time LLMs/AI started becoming good. I feel like the compiler problems with vliw could be solved to a degree with a purpose built ai
- spott 2mo agoI think it died before that, it was just that buried it then.
- 486sx33 2mo ago[dead]
- monocasa 2mo agoSo I feel like I need to write a blog post about this, but succinctly I think there's a good argument to be made that the issue wasn't the compiler despite popular wisdom. I don't even think it was the nature of unpredictable memory access times either as the itanium has a ton of special architectural hardware to handle unpredictable memory accesses (a lot of which are essentially some of the primitives that an OoO core uses for internal bookkeeping, just exposed architecturally). I just think the arch has a similarity to archs like cell where it was planned for a world without the end of dennard scaling and just stopped making sense when we weren't targeting scaling to 10Ghz consumer CPUs and beyond. The relatively fixed clock period that makes sense post ~2006 also means that the CPU architecture of that made the most sense ~2006 (Tomasulo OoO cores) continues to make sense, with most of the process gains going to just making bigger, wider cores.
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- twoodfin 2mo agoIt was also planned for a world where high-end CPUs were differentiated by their ability to run floating-point-heavy workloads with relatively predictable memory access patterns. The rise of the web—and databases behind it—as the dominant high-end, high-margin workload obsoleted that assumption. There’s a great presentation floating around where a Compaq-acquired-DEC engineer is trying to justify how great the OpenVMS port from Alpha to Itanium is going, despite benchmarks showing Alpha smoking Itanium running Apache.
- eej71 2mo agoI worked for a company that had a fairly large OpenVMS installation and had to make the transition from Alpha to Itanium. It required a considerable amount of work and the early iterations of Itanium did not provide a clear performance improvement over the final Alpha EV7z that we had been using in some GS1280s. Going by my faulty memory, I'd say it wasn't until Tukwila that it was a clear win over Alpha EV7z. By the time Tukwila arrived, it was pretty clear that Itanium's goose was already cooked.
- p_l 2mo agoEV7 were introduced after customers refused to upgrade to Integrity over crap performance.
- wbl 2mo agoIf only the Alpha had hung on.
- icedchai 2mo agoI have an AlphaServer in my collection (DS10.) For a 25+ year old system, it still feels pretty snappy!
- hypercube33 2mo agoI think I read at one point alpha had a 64bit cpu in the 90s that could have hit 1ghz but some bug held it back. I am having so much trouble finding these articles and stories about processors these days with AI and shitified Google. The other one I can't find I swear was a former AMD engineer talking about how Intel bet the farm on one ibm mainframe design but AMD went with an older architecture (under the hood of x86 for both) that was harder to deal with but ultimately runs faster and that's how we got ryzen. Maybe I'm just losing my mind.
- acdha 2mo agoThere was also a long piece by a former Intel chip designer who was incredulous about how much the Itanium team was promising numbers based on a very few hand-scheduled routines for FPU-limited code. I think there’s a solid argument that the design just wasn’t based on a correct understanding of what most CPUs did and over-indexed on the most performance-sensitive HPC code. I once helped run some HPC code on a test Itanium system and even there it was just so easy to fall out of the only patterns which performed well and end up slower than older Pentiums even before factoring price into the evaluation. > I said, wait I am sorry to derail this meeting. But how would you use a simulator if you don't have a compiler? He said, well that's true we don't have a compiler yet, so I hand assembled my simulations. I asked "How did you do thousands of line of code that way?" He said “No, I did 30 lines of code”. Flabbergasted, I said, "You're predicting the entire future of this architecture on 30 lines of hand generated code?" [chuckle], I said it just like that, I did not mean to be insulting but I was just thunderstruck. Andy Grove piped up and said "we are not here right now to reconsider the future of this effort, so let’s move on". https://www.sigmicro.org/media/oralhistories/colwell.pdf https://www.sigmicro.org/media/oralhistories/colwell.pdf > Davidson also pointed out two areas where academic research could create a blind spot for architecture developers. First, most contemporary academic research ignored CISC architectures, in part due to the appeal of RISC as an architecture that could be taught in a semester-long course. Since graduate students feed the research pipeline, their initial areas of learning frequently define the future research agenda, which remained focused on RISC. Second, VLIW research tended to be driven by instruction traces generated from scientific or numerical applications. These traces are different in two key ways from the average system-wide non-scientific trace: the numerical traces often have more consistent sequential memory access patterns, and the numerical traces often reflect a greater degree of instruction-level parallelism (ILP). Assuming these traces were typical could lead architecture designers to optimize for cases found more rarely in commercial computing workloads. Fred Weber echoed this latter point in a phone interview. Bhandarkar also speculated that the decision to pursue VLIW was driven by the prejudices of a few researchers, rather than by sound technical analysis. http://courses.cs.washington.edu/courses/csep590/06au/projects/history-64-bit.pdf http://courses.cs.washington.edu/courses/csep590/06au/projec...
- kmeisthax 2mo ago
- bluedino 2mo agoI wonder if most people kept them around just so they don't have to port their apps or migrate to something new. I worked at an HP shop, and Itanium ran HP/UX so they kept running their business on their PickBASIC (and whatever database that I've forgotten the name of) system
- jcranmer 2mo agoI recall opening up the Itanium manual, and by the end of the architecture description, just despairing of the thought of trying to write a compiler for it. Itanium, I think, was ultimately a victim of its weirdness: it's too weird to really comfortably write assembly by hand; the compilers weren't really capable with its weirdness, so "regular" code was worse off than you'd normally expect. Raymond Chen has pointed out in several articles how the hardware took advantage of C's UB to do some really weird things--and this is an era where most developers expected UB to really be just implementation-defined behavior. Combine that with the fact that the hardware development process seems to have been compromised from the start (if you told me the hardware architects never looked at anything other than 30-instruction traces of BLAS kernels, I'd believe you), and the insane hype that was built up for it... it's not surprising that it had an extremely underwhelming launch.
- alphabeta3r56 2mo agoIt's more simple. Online bin packing problem is simpler to solve and has more optimal solutions with smaller chunks
- 20k 2mo agoPeople have tried all kinds of techniques for VLIW, including techniques that are much better than a purpose built AI, AI isn't a magic silver bullet. Fundamentally there's no reason you can't analyse a piece of code to death, and maximally extract parallelism out of it The fundamental issue is that there simply doesn't exist enough information to be able to extract the necessary parallelism without a rewrite, its the same issue as trying to autovectorise. You can do it to some degree, but it doesn't work in practice to be able to fill out a very wide architecture with reasonable efficacy The SIMT programming model has proven to be much more successful vs trying to autovectorise or mash things into a VLIW architecture
- ggm 2mo agoFrom memory, Glasgow University CS had serious buy in to VLIW models of computation for a while, predating Itanium. There was good reason for believing it might have some interesting behaviours. I think they worked on languages targetting it, data models, things like reversible computation, long lived processes.
- adrian_b 2mo agoThe so-called "SIMT programming model" is a term from the obfuscated jargon that NVIDIA has introduced for CUDA, where they have renamed almost all traditional terms used for decades in the computing literature. The "SIMT programming model" is the same thing that in 1963 was called "Parallel DO" (from the name of the loop statement in FORTRAN), and later it was more frequently called "Parallel FOR", like in the C/C++ version of OpenMP. In the influential research paper on which later the programming language Occam was based, C.A.R. Hoare referred to the same thing as "an array of processes". The "SIMT programming model" just means that you write iterative structures where the programmer guarantees that the iterations are independent (unless specified otherwise), so that their order of execution does not matter. In CUDA it is slightly less obvious than in OpenMP that the so-called "CUDA kernel" is the body of a loop, because the header of the loop is not adjacent, but it is placed elsewhere in the file. The essential difference between the "SIMT programming model" and writing a "for" loop in C is that the compiler is certain that the iterations are independent. For auto-vectorization, the compiler must prove that they are independent, which can be difficult. Compiling for a VLIW CPU is in general a much more difficult problem than auto-vectorization (which implements data parallel processing with multiple cores and/or SIMD cores). A VLIW CPU is able to execute in parallel distinct instructions, not only the same kind of operation like a SIMD CPU, but in most cases there are complex restrictions about what kind of instructions may be combined. It can be too difficult for a compiler find a schedule for the instructions in such a way that this would allow a maximum number of instructions executed per clock cycle. Probably the worst part is that it is unlikely to be able to keep busy all execution units without speculative execution of the instructions that are beyond conditional jumps. For these, it is pretty much impossible to guess an optimal schedule at compile-time, because it would change during execution when the same code (in a function or in a loop body) is executed again. A CPU with dynamic instruction scheduling a.k.a. with out-of-order execution, will change the instruction schedule depending on the predicted branches, with much better chances of keeping busy the execution units. In HPC applications, where Itanium worked best, it is possible to predict the branches at compile-time quite well, so a compiler has a chance to find an acceptable instruction schedule, unlike in more general-purpose applications, which are hard to predict. A VLIW CPU also has speculative execution and a branch predictor, because these are needed in any pipelined CPU. But unlike in an OoOE CPU, the speculative execution handles only complete bundles of instructions that are executed in a given clock cycle. A bundle of instructions may be executed speculatively or not, but the CPU cannot extract speculatively individual instructions from a set of bundles and combine them into a bundle that would occupy all execution units, like in an OoOE CPU.
- nl 2mo ago> Ironically, it died around the time LLMs/AI started becoming good. What? I think maybe you are confusing Itanium with something else? Development on itanium stopped in 2013: > On 31 January 2013 Intel issued an update to their plans for Kittson: it would have the same LGA1248 socket and 32 nm process as Poulson, thus effectively halting any further development of Itanium processors.[1] It's true that it shipped until 2021, but I think you had to already have previous orders to get that. [1]https://en.wikipedia.org/wiki/Itanium https://en.wikipedia.org/wiki/Itanium
- ndiddy 2mo agoEven if the magical Itanium compiler did exist, Itanium would have still lost to AMD64. As soon as you introduce anything that doesn't behave in a statically predictable manner (multitasking, or virtualization, or even an application that processes unpredictable input like a web backend or database), your performance drops down to a fraction of what a similarly priced AMD64 chip could do. VLIW is great for some very specific workloads like HPC, but Intel should have never tried to replace x86 with it.
- MBCook 2mo agoThe lack of licensing to other companies was clearly a POWERFUL incentive. Imagine how much money they could make if that pesky AMD went away.
- p_l 2mo agoIIRC it was major part of intel's roadmap to establish it so that "future" of PC cpus would be locked down to Intel/HP partnership. And back then VIA was still noticeable competitor!
- icedchai 2mo agoItanium was effectively dead once Intel adopted AMD's x86-64. It just remained a zombie for another 15+ years.
- MBCook 2mo agoIt was neat to live through the era where CPUs constantly got faster and they were willing to try such oddball stuff. For such a long time it became “faster and more cores, don’t be different” and just didn’t seem as interesting. Apple Silicon had been very interesting to me. I’m really hoping to see a stronger ARM push on Windows, both because I know it can be great and because it’s just interesting. Windows has never had to switch architectures (for consumers) or support two at once for any reasonable population. Also, whatever happened to mill? We used to get posts about them all the time. And I wonder what would have happened to Power if they had the 3rd party fabs that exist today instead of being stuck with what IBM could make in-house.
- sedatk 2mo agoA historical note: Windows XP 64-bit Edition that was mentioned in the article, was Itanium-specific. It was based on XP kernel while Windows XP x64 Edition (for AMD64 architecture) was based on Windows Server 2003 kernel. Because of that, Windows XP x64 Edition had some significantly different performance characteristics compared to other Windows XP editions. If anything, it was closer to Vista than XP in some aspects.
- twoodfin 2mo agoI would love to read the Microsoft PM spec for this product. Who in the world were they making it for? Itanium never made it into the consumer-class hardware that was XP’s audience. AFAIK, Intel never even published a roadmap for that to happen! Maybe a proof of concept they shipped as a demonstration of loyalty to Intel?!
- mrpippy 2mo agoThere were Itanium workstations (https://www.openpa.net/systems/hp_i2000.html https://www.openpa.net/systems/hp_i2000.html, https://www.openpa.net/systems/hp_zx2000.html https://www.openpa.net/systems/hp_zx2000.html), but of course these quickly crashed and burned with the rest of Itanium
- twoodfin 2mo agoYeah, I had forgotten that by the Windows XP/Server 2003 era, the latter was definitely a server product, with XP targeting the workstation world. That still seems weird to me. If I had to rely on a PC for high-end work in that period, I wanted the server SKU.
- pjmlp 2mo agoBetween 2000 and 2003, I used Windows Server as desktop at work, after a short period of dual booting between Windows 2000 and Red-Hat Linux, which I stop doing when routinely rebooting into Windows for support started being a frequent habit. Thus I fully switched to Windows Server to be able to check the same issues as the customers had, and since we only supported big iron UNIX during those years, I would anyway use telnet / X Windows to connect to those machines.
- tech234a 2mo agoI wonder if people are able to get Windows Server 2008 R2 to run on this yet as well. That was the last Windows OS to support Itanium, and it received updates until January 14, 2020. EDIT: there was also an additional patch released in May 2020 according to https://en.wikipedia.org/wiki/Windows_Server_2008_R2#Itanium https://en.wikipedia.org/wiki/Windows_Server_2008_R2#Itanium
- qingcharles 2mo agoWild that shipments of Itaniums didn't end until 2021.
- taspeotis 2mo agoI think HP had a big investment in Itanium and even sued Oracle to get them to keep supporting Itanium (they had contractually agreed to it, but Itanium was such a dead end...)
- Nursie 2mo agoThey did, IIRC back in the late 00s they were also paying IBM to port software to HP-UX on Itanium, because I remember I was given a machine to play with and was asked to produce builds of some components. From what I remember the only drama was that there was a missing pthread_ API implementation on the platform, might have been pthread_gettime or something. Compared to the HP-UX on PA-RISC box I had access to at the time, the performance was amazing!
- omnibrain 2mo agoThey had bet 100% on it killing PA-RISC and DEC Alpha. They ported HP-UX, OpenVMS and NonStop to it. All 3 of them were tangled up in long running enterprise and government contracts. They since discontinued HP-UX, offloaded OpenVMS and ported NonStop to x86-64.
- p_l 2mo agoItanium was essentially (incompatible) PA-RISC 3 - it originated as HP project and the direction to totally replace HPPA with Itanium was there from the start. Non-Stop got ported early on because they needed some hardware and clients were locked down. OpenVMS customers however balked about shifting to Itanium given that it was often slower than their existing Alpha boxes, leading to HP being forced to finish EV7 work and release another generation of Alpha chips (funnily enough, EV7 might have forked and lived on in Opteron/K8...)
- t1234s 2mo agowas there any advantage or special use case for running an itanium windows workstation instead of x86 back then?
- twoodfin 2mo agoMore than 3GB of application memory space and more than 4GB overall (including the NT kernel). At that time, this was starting to become a major issue at the high end of servers and workstations.
- kstrauser 2mo agoAnd then AMD64 came along and we immediately moved to 8GB servers, taking away the only real Itanium advantage.
- pjmlp 2mo agoYeah, in an alternative timeline AMD would not had the opportunity to come up with AMD64, and we had to suck up Itanium no matter what, and maybe they would be improved.
- WarOnPrivacy 2mo agoXGCJ6-Q6XGJ-BQ2QQ-BRWJ7-67X7W I used to have this key memorized.
- corvad 2mo agoMight need some background on this one.
- lode 2mo agoNever heard of this one either. FCKGW on the other hand still triggers muscle memory.
- WarOnPrivacy 2mo agoI had FCKGW-RHQQ2-YXRKT-8TG6W-2B7Q8 memorized too but I used XGCJ6 more often. Mostly for Virtual PCs that I was converting to hyper-v guests.
- WarOnPrivacy 2mo ago> Might need some background on this one. It's a VLK. During early XP days, Volume License Keys were widely accepted and when using them, XP would show as activated.
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