[sdiy] Cray history, was: Static ADC and DAC recommendations?

[cheater cheater]

Where did I put my tin foil hat... :^)

On Fri, Jan 18, 2013 at 3:47 PM, Paul Burns <paul at fitvideo.co.uk> wrote:
>
> That pdf is a good read. This is interesting to, and Mentions John Lacey
> half way through , about when he was with GHCQ before going out to assist
> the NSA ( The UK Foreign Office sent British specialists to design NSA
> computers? What the ??) where he met Norris, presumably through the Rand
> Corporation.
>
> http://www.chilton-computing.org.uk/acl/literature/reports/p011.htm
>
> regards
>
> Paul Burns
>
> -----Original Message-----
> From: cheater cheater [mailto:cheater00 at gmail.com]
> Sent: 18 January 2013 12:55
> To: Paul Burns
> Cc: sdiy diy
> Subject: Re: [sdiy] Cray history, was: Static ADC and DAC recommendations?
>
> Indeed, quite a bit of turmoil there - the NASA report was fairly scathing.
>
> On Fri, Jan 18, 2013 at 9:43 AM, Paul Burns <paul at fitvideo.co.uk> wrote:
>> Hi there , he may well have to do a lot of explaining , as he did in
>> this missive from a guy who went on to be communications CEO of NASA.
>>
>> http://www.mediafire.com/view/?3olonbu1tq02mft
>>
>> regards
>>
>> Paul
>> -----Original Message-----
>> From: cheater cheater [mailto:cheater00 at gmail.com]
>> Sent: 17 January 2013 23:40
>> To: Paul Burns
>> Cc: Phillip Harbison; sdiy diy
>> Subject: Re: [sdiy] Cray history, was: Static ADC and DAC recommendations?
>>
>> I read at some point Cray got so pissed off with the way things were
>> going (as influenced by management) that he shut down his whole lab,
>> built a factory hall 250 km away, and only started after all the
>> technical workers moved there :) Management wasn't allowed :) But
>> apparently after he was let off the leash he couldn't deliver, and
>> after being put on the back burner left the company. Read all about
>> it:
>> http://en.wikipedia.org/wiki/Seymour_Cray#CDC.27s_Chippewa_Falls_labor
>> atory
>>
>> Then, your uncle had to explain why CDC wasn't doing so well,
>> especially compared to IBM:
>>
>> http://tinyurl.com/ax8udh5
>>
>> (full url:
>> http://books.google.de/books?id=khwnFtEzTccC&pg=PA45&lpg=PA45&dq=john+
>> w+lace
>> y+cdc&source=bl&ots=Rk6pnA5tjo&sig=6FlpRZXxDpAUhbuHVm_mowMSxbM&hl=en&s
>> y+a=X&ei
>> =nYj4UJ7ZI8aQ4gTBs4DgDA&ved=0CCoQ6AEwAA#v=onepage&q=john%20w%20lacey%2
>> 0cdc&f
>> =false
>> )
>>
>> interestingly enough it's the first link that shows up if you search
>> for his name and "CDC"..
>>
>> Cheers
>>
>> On Thu, Jan 17, 2013 at 11:54 PM, Paul Burns <paul at fitvideo.co.uk> wrote:
>>> Thank you for the historical insight, my uncle is one John W. Lacey
>>> who was a top dog at CDC right from the outset ( he used to employ
>>> Seymour Cray ;-)
>>> )
>>> Regards
>>> Paul Burns.
>>>
>>>
>>> -----Original Message-----
>>> From: synth-diy-bounces at dropmix.xs4all.nl
>>> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Phillip
>>> Harbison
>>> Sent: 17 January 2013 22:41
>>> To: synth-diy at dropmix.xs4all.nl
>>> Subject: Re: [sdiy] Static ADC and DAC recommendations?
>>>
>>> cheater cheater wrote:
>>>> Wait a sec guys - I thought the usual approach was folding converters.
>>>> That is, you take the input signal, scale it to e.g. 0-1V, and see
>>>> if it's the upper or lower half [...]
>>>
>>> That essentially describes one type of ADC, the successive
>>> approximation variety. The other type is a flash converter, where you
>>> have enough comparators on the chip to do this all in parallel. The
>>> problem is flash converters obviously get exponentially complex as
>>> you
>> increase the accuracy.
>>> You'll need twice as many comparators to go from 4 bits to 5 bits, so
>>> anything beyond about 8 bits is prohibitive, and I've only seen it
>>> used in extreme applications like video ADCs where 8 bits per color
>>> is usually sufficient.
>>>
>>> Another problem is even with a flash ADC, you'll need some settling
>>> time so there's still the issue of delay time even if you don't
>>> consider
>> it clocked.
>>> I don't think a continuous output is possible or at least not
>>> realistic. I second the suggestion of using a sample rate high enough
>>> that you don't notice it is not continuous. An ADC capable of 200K
>>> samples per second should be good enough for audio.
>>>
>>> If you really need continuous signal processing, that is why we still
>>> have analog computers. In my younger days I had the opportunity to
>>> visit the McMorrow Labs, a research center on Redstone Arsenal
>>> (Huntsville, AL) that does simulations to test missile guidance
>>> systems. I was majoring in computer engineering so this was quite a
>>> thrill. They had a CDC-7600 which was the fast supercomputer in those
>>> days
>> (the Cray-1 was not yet shipping).
>>> Connected to the 7600 was a CDC-6600 which interfaced to a room of
>>> analog computers about the size of a hockey rink. I would guess there
>>> were about
>>> 200 to 300 analog computers each about the size to two 19" x 84" racks.
>>> I asked why they needed all these analog computers, which I
>>> considered to be fossils, when they had the fastest computer in the
>>> world downstairs. My guide explained that solving any one of these
>>> complex differential equations, each of which was handled by an
>>> analog computer, would bring that
>>> 7600 to its knees. The analog computers were the right tool for the
>>> job. The
>>> 7600 ran a Fortran program that read descriptions of differential
>>> equations to patch layouts for the analog computers. OK, it did a few
>>> other things. :)
>>>
>>> "If the only tool you have is a hammer, every problem looks like a
>>> nail." -- me
>>>
>>> --
>>> Phil Harbison
>>>
>>>
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>>
>