3 ms·

I'm not that knowledgeable about hardware, but the fact that they were using a "24 bit fixed point register" sounds like they were not using a commodity process

I'm not that knowledgeable about hardware, but the fact that they were using a "24 bit fixed point register" sounds like they were not using a commodity processor, even for 1991. I assume that the error described would simply not arise today on a modern CPU running Linux?

fit2rule 13y ago
The Motorola 56000 DSP's fit the description, and they are used everywhere - all throughout military-industrial applications. And yes, these bugs still occur - even on modern CPU's running Linux.
gcb0 13y ago
Medical and military equipment trove on outdated hardware just because they can save a few hundreds of dollars on a product that will cost thousands or millions by avoiding going thru the simple certification process for the new hardware. It's a simple case of beancounters saving little in obvious places and wasting a lot later (in engineer time, testing, recalls, and in this case soldier lifes) sadly, everyone in those industries buys that idiotic notion and repeat it like a mantra.
- bane 13y ago
  There's probably EMP hardening requirements that non-specialized processors don't meet.
- bronson 13y ago
  You've never worked for a military contractor have you? It's never black and white. Let's say you ran the project that converted the missile from the militarized rad-hard ceramic-capped chip ($$!) that's likely in there now to a nice and cheap off-the-shelf Arm7. Except you forgot about coefficient of expansion for 120degF middle-of-the-day Middle East launches. Your Arm7 flexes too much and loses some bits, your Patriot misses, the soldiers lose their lives, and now the parallel universe equivalent of you can spout off on Internet forums about how the military just doesn't respect traditional, proven designs and is always wasting money on following the latest trend. Also, you probably don't realize when the Patriot entered service? And the number of upgrades it's received?
  - rayiner 13y ago
    I'm going to print this out and frame it. Engineering isn't no cakewalk.
  - protomyth 13y ago
    Don't forget the fun of making sure the chip is built for an extended period of time to the exact specs that you started with.
- vonmoltke 13y ago
  In addition to what bronson already said: Once upon a time I did production support for a military radar power supply. One of my tasks is something we called Diminishing Material Sources (DMS). Basically, we had a system that would be produced over the course of 10 years and would need to be supported for a minimum 20 years after it was produced. The design, of course, had to be complete before production started, so tack 7 years on to the front. Not every supplier would want to keep producing specific parts long enough to support our needs, so if something was going to drop out of production I had to perform a DMS analysis to find a substitute. That involved either finding a drop-in replacement or redesigning part of the circuit. The former was sometimes painful, because a new supplier would need to have its parts evaluated for compatibility, which meant dozens of hours of testing parts and testing boards with parts installed. The latter was an order of magnitude more painful. Any change to the design meant a partial or full re-qualification, and the cost could be anywhere from hundreds of thousands to tens of millions of dollars. Anything that involved changing the circuit board automatically went to the right side of that scale. The "simple certification process" involves intensive environmental stress and screening testing: thermal shock on assembled boards (-40C to 70C transition in 30s); operational thermal cycling (repeated cycles of -40C to 70C with the hardware operating); and operational vibration testing (several tens of minutes operating while attached to a table shaking violently enough to liquefy your internal organs). There is also accelerated life testing, which determines if the modified design will meet the system longevity requirements. Depending on what changed and the system complexity, this may have to be repeated at multiple subsystem levels above the affected board. For this reason we bent over backwards not to change the design unless we had no other choice. Design changes brought too much risk for us, our customers, and our end users. For this reason the military much prefers the spiral upgrade process for maintaining long-lived systems: once you get some practical experience with the current version, start work on an upgrade package that contains multiple fixes and enhancements at once and switch to that when it is ready. Sometimes it is even possible to retrofit existing systems with the spiral upgrades.

fit2rule 13y ago

The Motorola 56000 DSP's fit the description, and they are used everywhere - all throughout military-industrial applications. And yes, these bugs still occur - even on modern CPU's running Linux.

gcb0 13y ago

Medical and military equipment trove on outdated hardware just because they can save a few hundreds of dollars on a product that will cost thousands or millions by avoiding going thru the simple certification process for the new hardware. It's a simple case of beancounters saving little in obvious places and wasting a lot later (in engineer time, testing, recalls, and in this case soldier lifes) sadly, everyone in those industries buys that idiotic notion and repeat it like a mantra.

bane 13y ago
There's probably EMP hardening requirements that non-specialized processors don't meet.
bronson 13y ago
You've never worked for a military contractor have you? It's never black and white. Let's say you ran the project that converted the missile from the militarized rad-hard ceramic-capped chip ($$!) that's likely in there now to a nice and cheap off-the-shelf Arm7. Except you forgot about coefficient of expansion for 120degF middle-of-the-day Middle East launches. Your Arm7 flexes too much and loses some bits, your Patriot misses, the soldiers lose their lives, and now the parallel universe equivalent of you can spout off on Internet forums about how the military just doesn't respect traditional, proven designs and is always wasting money on following the latest trend. Also, you probably don't realize when the Patriot entered service? And the number of upgrades it's received?
- rayiner 13y ago
  I'm going to print this out and frame it. Engineering isn't no cakewalk.
- protomyth 13y ago
  Don't forget the fun of making sure the chip is built for an extended period of time to the exact specs that you started with.
vonmoltke 13y ago
In addition to what bronson already said: Once upon a time I did production support for a military radar power supply. One of my tasks is something we called Diminishing Material Sources (DMS). Basically, we had a system that would be produced over the course of 10 years and would need to be supported for a minimum 20 years after it was produced. The design, of course, had to be complete before production started, so tack 7 years on to the front. Not every supplier would want to keep producing specific parts long enough to support our needs, so if something was going to drop out of production I had to perform a DMS analysis to find a substitute. That involved either finding a drop-in replacement or redesigning part of the circuit. The former was sometimes painful, because a new supplier would need to have its parts evaluated for compatibility, which meant dozens of hours of testing parts and testing boards with parts installed. The latter was an order of magnitude more painful. Any change to the design meant a partial or full re-qualification, and the cost could be anywhere from hundreds of thousands to tens of millions of dollars. Anything that involved changing the circuit board automatically went to the right side of that scale. The "simple certification process" involves intensive environmental stress and screening testing: thermal shock on assembled boards (-40C to 70C transition in 30s); operational thermal cycling (repeated cycles of -40C to 70C with the hardware operating); and operational vibration testing (several tens of minutes operating while attached to a table shaking violently enough to liquefy your internal organs). There is also accelerated life testing, which determines if the modified design will meet the system longevity requirements. Depending on what changed and the system complexity, this may have to be repeated at multiple subsystem levels above the affected board. For this reason we bent over backwards not to change the design unless we had no other choice. Design changes brought too much risk for us, our customers, and our end users. For this reason the military much prefers the spiral upgrade process for maintaining long-lived systems: once you get some practical experience with the current version, start work on an upgrade package that contains multiple fixes and enhancements at once and switch to that when it is ready. Sometimes it is even possible to retrofit existing systems with the spiral upgrades.