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Raymond Chen recently posted a ten-part introduction to the ia64 architecture. Rapidly teaching me that while I might be able to write a brainfuck to perl compiler in a few minutes, there's no way in a million years that I'll ever be able to write a good compiler that targets ia64.
- Part 1: Warming up
- Part 2: Instruction encoding, templates, and stops
- Part 3: The Windows calling convention, how parameters are passed
- Part 3b: How does spilling actually work?
- Part 4: The Windows calling convention, leaf functions
- Part 5: The GP register, calling functions, and function pointers
- Part 6: Calculating conditionals
- Part 7: Speculative loads
- Part 8: Advanced loads
- Part 9: Counted loops and loop pipelining
- Part 10: Register rotation
The Itanium is a 64-bit EPIC architecture. EPIC stands for Explicitly Parallel Instruction Computing, a design in which work is offloaded from the processor to the compiler. For example, the compiler decides which operations can be safely performed in parallel and which memory fetches can be productively speculated. This relieves the processor from having to make these decisions on the fly, thereby allowing it to focus on the real work of processing.
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Grelb's Reminder:
Eighty percent of all people consider themselves to be above
average drivers.
(Score: 2) by turgid on Sunday August 09 2015, @10:18AM
At the time of the itanic hysteria, while all the big Unix server companies were slitting their own throats having drunk intel's and HP's marketing Kool Aid, there were some voices of reason. Linus was particularly insightful [yarchive.net] as always.
I spoke to a guy from Sun who'd been in the business since the 1970s and he told me an interesting story about itanic. It was a research project that never lived up to the promises, and all it needed was "better compilers." We're still waiting.. The problem with itanic is that it's a scaled up DSP. It's only good for executing FORTRAN loops. In real-world general use, it can't cope with highly dynamic work loads. See Linus' comments above.
I refuse to engage in a battle of wits with an unarmed opponent [wikipedia.org].
(Score: 0) by Anonymous Coward on Sunday August 09 2015, @11:19AM
The problem with itanic is that it's a scaled up DSP. It's only good for executing FORTRAN loops.
From what I saw it was very good at "embarrassingly parallel workloads" and not really good at other stuff.
The problem with that was it was very expensive and power hungry, and embarrassingly parallel workloads are also easily run on multiple AMD64 CPUs/nodes (which were cheaper and performed better when you got messier workloads). For the price of one of those HP Itanic servers you could buy two or more AMD64 machines and do that parallel workload faster.
Thus the Itanic only made sense for a few people.
(Score: 0) by Anonymous Coward on Sunday August 09 2015, @11:43AM
I knew a Debian guy who had an itanic server for doing the itanic build. He used to use the waste heat for drying his clothes.
(Score: 0) by Anonymous Coward on Sunday August 09 2015, @02:16PM
(Score: 0) by Anonymous Coward on Sunday August 09 2015, @05:25PM
> I spoke to a guy from Sun ...
> It's only good for executing FORTRAN loops. In real-world general use, it can't cope with highly dynamic work loads.
That's funny that you took the word of a competitor as gospel. From the second generation onward Itanium had some of, and often the best, TPC/$ benchmarks. That's Transaction Processing Council which is basically a database benchmark. Sparc, on the other hand, always trailed the pack relying on the inertia of the market, but they could only coast for so long which is part of the reason sun is now owned by one real asshole called larry ellison.
(Score: 2) by turgid on Sunday August 09 2015, @09:23PM
I didn't take what he said as gospel. I'm not religious. But it did concur with what other people (computer scientists and engineers) were saying at the time. And despite all the hype, I never actually saw a working itanic system but I spoke to some guys who rented one for running some FORTRAN that they'd written to simulate nuclear reactors.
I refuse to engage in a battle of wits with an unarmed opponent [wikipedia.org].