4 ms·

> You begin to suspect that a problem you are having is due to a hardware problem, where the processor is not conforming to its specification. What is the prob

by henning 18y ago

> You begin to suspect that a problem you are having is due to a hardware problem, where the processor is not conforming to its specification. What is the probability of that happening? The last time this happened in any significant way was the FDIV bug on the original Pentium. That was 1994. It was extremely rare in practice. That's a ridiculous question and completely irrelevant to 99%+ of software development. I agree with sofal that reading all these "you should think and work exactly the way I do or else you're stupid" pieces I see get really fucking old. Fucking around with disassemblers and assembly language instead of just running on AMD chips instead of Intel until the problem gets resolved is a massive waste of time.

dfranke 18y ago
I think you're missing the point. He's not looking for hardware hackers. He's looking for people who know how a computer works. God job candidates should have no trouble answering that question regardless of whether they've actually ever seen a CPU bug.
- henning 18y ago
  IMO the most pragmatic way to deal with the question as posed requires no knowledge of computer hardware. If you want hardware knowledge, ask about pointer arithmetic and memory hierarchies, which is still mostly irrelevant to what most developers spend most of their time doing. Before someone launches into a jihad about memcached and load balancing and super high-scale stuff, most people never have to do that.
- sofal 18y ago
  "You begin to suspect that a problem you are having is due to a hardware problem, where the processor is not conforming to its specification. How would you track this down? How would you prepare a bug report for the chip manufacturer, and how would you work around the problem?" Actually he's looking for people who know how to track down a processor bug, report it appropriately to a manufacturer, and work around it. Would it demonstrate complete incompetence and a failure of my CS education to answer: "I would learn how to track it down, learn how to submit a report, and then figure out how to work around it."? It's one thing to expect job candidates for AdaCore to be experienced embedded-system developers, but it's another thing to expect university CS departments to throw their resources into that small corner of computer science so that he can hire new grads without having to bring them up on embedded systems work. I'm sure that CS departments with tons of resources can provide an embedded-systems track for undergraduates.
- michaelneale 18y ago
  Why can't they teach both - the high level reality of today, but also down to the metal (its how I did it, although the "high level" back then was miranda and pascal !).
eugenejen 18y ago
It really depends on the context of your products. If you are working on embedded systems, your have to know when your compiler and hardware has problems. And not all software products works like web based software. Web based software has its problem domain like scaling, security, which is very different to other area of software systems, Another case is for programmers working in Operating Systems. I remember like this url http://marc.info/?l=openbsd-misc&m=118296441702631 http://marc.info/?l=openbsd-misc&m=118296441702631 was mentioned a while ago when OpenBSD group found a lot of hardware bugs in Core 2 Duo. The danger is the misplaced blind faith on the reliability of the system that we are using. And teaching only Java to students is a sin for computer science to build such a blind faith.
- henning 18y ago
  I am the last one to defend using Java as a teaching language. The professor in the OP seems to be angry that there are people who spend their time doing things other than making toys for the Pentagon, and I say I don't give a hoot about his Ada silliness.
  - eugenejen 18y ago
    I was in fact a student who took his compiler class 12 years ago in NYU. A lot of students didn't like his classroom presentation because he would rather talk topics that was not covered inside textbooks (books are for reading at home for homeworks and project). And his class is a project based so in fact the only factor for the grade is the project. I had to write a code generator for GCC AST tree to x86 assembly in the subset of Ada that I chose. In fact, the only exciting part is to write this backend, which is beyond descriptions unless you did that. He just belongs to a very old school in this discipline that holds the belief that you need to know what are you building from the lowest level components. You don't need to be an expert unless you work in that domain. But at least you are not clueless. My recollection may be wrong. But I thought his Ph.D. was in fact in Chemistry. And he built and sold Cobol compilers before he worked on SETL language and Ada.
    - michaelneale 18y ago
brent 18y ago
I have worked with more than one microcontroller in the last few years that was not operating to spec. On top of that, in one case we couldn't even do a work around due to compiler error. I think the problem is a lot more prevalent than you think.
- henning 18y ago
  Was that some random product from some 3rd party outfit, or a flagship CPU from a major manufacturer that's installed on tens of millions of computers?
shard 18y ago
The Pentium has 70-something errata, each of which had to be found and worked around by somebody. Now consider the range of microprocessors and microcontrollers used in handheld devices, appliances, and other electronic equipment. I personally have run into compiler issues for Lattice FPGAs where it was outputting incorrect binaries. And I couldn't run on another chip until the problem got resolved, because hardware was being developed in tandem with the firmware and we had already progressed beyond the point of component selection. I understand that this is beyond your experience. These are obviously not the droids you are looking for.

by henning 18y ago

dfranke 18y ago

I think you're missing the point. He's not looking for hardware hackers. He's looking for people who know how a computer works. God job candidates should have no trouble answering that question regardless of whether they've actually ever seen a CPU bug.

henning 18y ago
IMO the most pragmatic way to deal with the question as posed requires no knowledge of computer hardware. If you want hardware knowledge, ask about pointer arithmetic and memory hierarchies, which is still mostly irrelevant to what most developers spend most of their time doing. Before someone launches into a jihad about memcached and load balancing and super high-scale stuff, most people never have to do that.
sofal 18y ago
"You begin to suspect that a problem you are having is due to a hardware problem, where the processor is not conforming to its specification. How would you track this down? How would you prepare a bug report for the chip manufacturer, and how would you work around the problem?" Actually he's looking for people who know how to track down a processor bug, report it appropriately to a manufacturer, and work around it. Would it demonstrate complete incompetence and a failure of my CS education to answer: "I would learn how to track it down, learn how to submit a report, and then figure out how to work around it."? It's one thing to expect job candidates for AdaCore to be experienced embedded-system developers, but it's another thing to expect university CS departments to throw their resources into that small corner of computer science so that he can hire new grads without having to bring them up on embedded systems work. I'm sure that CS departments with tons of resources can provide an embedded-systems track for undergraduates.
michaelneale 18y ago
Why can't they teach both - the high level reality of today, but also down to the metal (its how I did it, although the "high level" back then was miranda and pascal !).

eugenejen 18y ago

It really depends on the context of your products. If you are working on embedded systems, your have to know when your compiler and hardware has problems. And not all software products works like web based software. Web based software has its problem domain like scaling, security, which is very different to other area of software systems, Another case is for programmers working in Operating Systems. I remember like this url http://marc.info/?l=openbsd-misc&m=118296441702631 http://marc.info/?l=openbsd-misc&m=118296441702631 was mentioned a while ago when OpenBSD group found a lot of hardware bugs in Core 2 Duo. The danger is the misplaced blind faith on the reliability of the system that we are using. And teaching only Java to students is a sin for computer science to build such a blind faith.

henning 18y ago
I am the last one to defend using Java as a teaching language. The professor in the OP seems to be angry that there are people who spend their time doing things other than making toys for the Pentagon, and I say I don't give a hoot about his Ada silliness.
- eugenejen 18y ago
  I was in fact a student who took his compiler class 12 years ago in NYU. A lot of students didn't like his classroom presentation because he would rather talk topics that was not covered inside textbooks (books are for reading at home for homeworks and project). And his class is a project based so in fact the only factor for the grade is the project. I had to write a code generator for GCC AST tree to x86 assembly in the subset of Ada that I chose. In fact, the only exciting part is to write this backend, which is beyond descriptions unless you did that. He just belongs to a very old school in this discipline that holds the belief that you need to know what are you building from the lowest level components. You don't need to be an expert unless you work in that domain. But at least you are not clueless. My recollection may be wrong. But I thought his Ph.D. was in fact in Chemistry. And he built and sold Cobol compilers before he worked on SETL language and Ada.
  - michaelneale 18y ago

brent 18y ago

I have worked with more than one microcontroller in the last few years that was not operating to spec. On top of that, in one case we couldn't even do a work around due to compiler error. I think the problem is a lot more prevalent than you think.

henning 18y ago
Was that some random product from some 3rd party outfit, or a flagship CPU from a major manufacturer that's installed on tens of millions of computers?

shard 18y ago

The Pentium has 70-something errata, each of which had to be found and worked around by somebody. Now consider the range of microprocessors and microcontrollers used in handheld devices, appliances, and other electronic equipment. I personally have run into compiler issues for Lattice FPGAs where it was outputting incorrect binaries. And I couldn't run on another chip until the problem got resolved, because hardware was being developed in tandem with the firmware and we had already progressed beyond the point of component selection. I understand that this is beyond your experience. These are obviously not the droids you are looking for.