SV: Re: [sdiy] Roland DCOs

[Veronica Merryfield]

I once worked with some early Transputer T405s that had the halt and  
catch fire bug. One of the lesser, thankfully, used instructions would  
turn on a transistor that had a missing resistor thus would short the  
power to ground, halting the cpu as the power level dropped and would  
get so hot the plastic dip would flame. I had a special cut of the  
compiler and assembler to avoid using the instruction. We later got  
new versions and I had the fun of executing a very short program and  
watching :)

That is a fun silicon bug :)

On 28-Feb-08, at 5:44 AM, karl dalen wrote:

> Just as a tiny side note. Thats Intels original, we have no idea if
> the silicon where redesigned coming from other wendors and there are  
> many
> to chose from. Also there are plenty of clones under different  
> labeling,
> altought 8253, 8254 was the system timer chip in 8088 286, 386 PC's  
> for
> quite some time. Inside those old PC's there are loads of these chips
> in them particularly 8088-86. Anyway hilarious bugs alright!!!
>
> Reg
> KD
>
> --- Ingo Debus <debus at cityweb.de> skrev:
>
>>
>> Am 25.02.2008 um 22:34 schrieb Tom Wiltshire:
>>
>>>>>
>>>>> What I wanted to know is if anyone has built a DCO along these
>>>>> lines, and what they discovered. I've wondered about doing it
>>>>> myself since the 82C54 triple counter chips are only a few pounds
>>>>
>>>> AARGH! The nastiest chip I ever came across!!
>>>
>>> I'd be interested to hear why. It looks like a pretty straight-
>>> forward IC from the datasheet.
>>
>> Didn't think I'd ever touch that datasheet again, but here it is:
>> http://download.intel.com/design/archives/periphrl/docs/23124406.pdf
>>
>> Here's the crucial sentence, page 16, note 3:
>> "Low-going glitches that violate tPWH, tPWL may cause errors
>> requiring counter reprogramming."
>>
>> Yes, that's very true, I found it out the hard way. This chip can
>> forget what it was programmed to do. It simply stops working and has
>> to be re-programmed. Doesn't happen very often (seldom enough that I
>> missed that bug in the first prototypes), but it does happen.
>>
>> I couldn't ever catch any short glitches in the clock signal (only a
>> 100MHz scope back then). But note there's also a tWC and tWG
>> specified. So not to violate that you'd have to watch the clock or
>> gate when accessing the '54 from the microprocessor. That's almost
>> impossible to do. I suspected that I didn't violate the tPWH, tPWL
>> specs but rather the tWC and tWG which crashed the chip.
>>
>> Ingo
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