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Alan60
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re: It always worked before, so you broke it
Alan60   5/20/2011 9:29:31 PM
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Been there, done it, got the company golf shirt. Years ago we had a hydraulic problem, excess pressure when braking. The redesign fix was messy, even for hydraulics. The $1M machine was down and people were not happy. I suggested a SW workaround to control deceleration, which we did and were soon back up running. However, word got around that I had to fix the SW to get the machine running. Unfortunately now I have to think twice before helping others.

DutchUncle
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re: It always worked before, so you broke it
DutchUncle   5/20/2011 8:10:24 PM
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Sometimes this is all in the software domain. Reviewing DOS driver code while writing new interface code on an ISA plug-in board, I found some code that seemed to have a race condition and asked about it. Since this had been written by one of the original product group, now a technical leader, and had been working for years, my question was disdained and dismissed out of hand. A mere few months later, intractable customer problems were blamed on my interface code. I finally traced it back the the same DOS driver code. Turned out this was the first customer PC system we had seen at whatever speed it was (500 MHz?) and it was the first time that the PC was fast enough to catch the race condition. Now it was still my fault for not having pushed harder when I found the problem before.

jimfordbroadcom
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re: It always worked before, so you broke it
jimfordbroadcom   5/20/2011 7:02:34 PM
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Well, I've worked with enough boneheaded software types who didn't know anything about hardware to say that you are the exception, Tim. Embedded engineers who know both are worth their weight in gold, even if boneheaded managers don't realize it. I totally agree with zeeglen; forget the finger-pointing and just figure out what's not working. Sometimes it's both H/W and S/W!

zeeglen
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re: It always worked before, so you broke it
zeeglen   5/20/2011 6:41:20 PM
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This reminds me of a time when a watchdog timer would sporadically time out when a processor took too long to execute a command/response sequence on a control bus. This was a new product in both HW and SW, and the late night sessions in the labs were not burdened by "it's a HW fault / no it's a SW fault". We just admitted that nobody knew yet where the fault was and we had to work together to find it. Finally, using an analog scope (digital scopes had not been invented yet) the SW guy and myself saw an event whiz by that the timeout occurred within the 1 second allocated time of the hardware. I took another look at the hardware, a long-chain ripple counter and realized that the guy who designed this had done the stage count based on a complete cycle at the final stage. He forgot that the timeout actually occurred on the rising edge HALFWAY through the cycle. Solution: knife and green wire. Lesson learned: Never assume HW or SW. Test, test, test....

Tombo0
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re: It always worked before, so you broke it
Tombo0   5/19/2011 1:27:39 PM
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I deal with this everyday

old account Frank Eory
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re: It always worked before, so you broke it
old account Frank Eory   5/18/2011 10:35:10 PM
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Interesting that in a new system -- new hardware and new software -- what ultimately turned out to be a signal integrity problem was blamed on software. "Mechanical and hardware assemblers said it was obviously software." And management simply took their word for it, without any data to back up that claim?

jnissen
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re: It always worked before, so you broke it
jnissen   5/18/2011 10:20:04 PM
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Been there done that! Don't care to repeat it!

Dave33
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re: It always worked before, so you broke it
Dave33   5/18/2011 8:30:24 PM
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I've written and debugged firmware for many years and I can really relate to this story. Solving problems like those described in the story take time and a very good engineer. Unfortunately there's no way to measure the difficulty of a problem so there's no way to measure the value of the solution. Managers usually just look at how long you took and draw their own conclusions.

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As data rates begin to move beyond 25 Gbps channels, new problems arise. Getting to 50 Gbps channels might not be possible with the traditional NRZ (2-level) signaling. PAM4 lets data rates double with only a small increase in channel bandwidth by sending two bits per symbol. But, it brings new measurement and analysis problems. Signal integrity sage Ransom Stephens will explain how PAM4 differs from NRZ and what to expect in design, measurement, and signal analysis.

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