Spartan 3 termination question (DCI)

Austin,
>
>Wow.  Sooooo much current!
>
 Save your sarcasm for an instance in which it is merited.

 Peter's claim of "zero additional system power" was inaccurate, 
especially coming after the "urban legend" lead-in.

 If he has a problem with me pointing out the per bank overhead
of DCI for V2 and S3 parts, I'm sure he'll speak up about it.

 In a small Spartan3 design drawing little current on VCCINT,
power consumption would be dominated by "sooooo much current",
especially if using 33 ohm VRP/N resistors as you suggested
earlier in the thread.

 It would be much better to shut down the VRP/VRN outputs after
configuration when DCIUpdateMode=Quiet, which would eliminate
the DCI power overhead completely for series DCI.

 When last I checked in detail (Fall 2003), all of Xilinx's
power estimation tools, published data, and Answer Records
failed to properly report static DCI supply current, for both
per-bank overhead and per-input parallel termination.

 As for the rest of your post, I could point out in detail the
various errors and omissions you've made, but I don't have the
time or patience tonight to explain things that should have 
been properly documented in the Virtex2 application notes and
datasheets long ago.

Brian



Austin Lesea <austin@xilinx.com> wrote in message news:<cd3o2s$npd3@cliff.xsj.xilinx.com>...
>
>Brian,
>
>LVDCI_33 is 60 mA for the reference resistors.  For the whole bank.
>
>Wow.  Sooooo much current!  Face it:  setting the reference for the 
>entire bank does take some power (in this case 3.3V X 60 mA or 200 
>milliwatts.  I am pretty sure this is not going to "break the bank."
>
>Yes, and if you just had to have all 8 banks use DCI, that would be 8 
>times as much current.  I suggest that you confine the DCI interfaces to 
>those banks that need them, not just for the 200 milliwatts.
>
>Freeze DCI has nothing to do with it.  The DCI circuit has to solve for 
>1/2 R, R and 2R, so the average current consumption is higher than it 
>would be for R alone.
>
>One trick you can use to cut it in half is to use 100 ohm reference 
>resistors, and use LVDCI_DV2 (divide by two) to get 50 ohm drive.
>
>Now you have 100 milliwatts dissipated for the feature of using DCI  in 
>the bank.
>
>If you are thinking "why did they not use 10X reference resistors? (to 
>lower power per bank)" the answer is very simple:  the noise in a 
>typical system would trash a higher impedance reference system, and the 
>feature would have to be abandoned (or fixed)  -- sound familiar?.  From 
>the first appearance of DCI in Virtex II, it has been a solid feature in 
>every device since.
>
>DCI updating is only an issue when you cross between two banks, and even 
>then only with the parallel interfaces where it adds some small amount 
>of jitter.  Freezing the updates allowed customers who did not read that 
>they should not go across banks to modify the bitstream, rather than 
>re-design their pcbs.  It also allowed the highest speed interfaces to 
>have more timing margin (budget) which makes memory interfacing easier.
>
>It is always preferable to provide the customer with solutions that 
>involve changing bits, rather than making new boards (and them failing 
>to place the orders that we desire).  Now we have three different DCI 
>options:  regular (runs all the time changing +/- one trim), changes 
>only when reguired, and "frozen" after matching (at configuration time).
>
>Austin
>

Brian,

I would appreciate it if you did detail every single omission, 
distortion, or mis-representation.

In fact, I demand it, or an apology.  As you know, when I make a 
mistake, I own up to it immediately.  I expect no less from others.

To say "if you are already drawing no power, then 200 mW is a lot of 
power" is a pretty inane response.

Obviously.  Your point?

Peter's comment is perfectly accurate:  series terminations dissipate 
virtually no power in the series termination resistors.

As for my sarcasm, although sarcasm is known as the "weapon of the 
weak." it does serve a purpose to emphasize a point.  I reserve the 
right to be as entertaining as possible.

Thanks for the suggestion of turning the reference resistors off.  Not a 
bad idea at all.

Power estimation tools lag the rest of the tools.  Entering in the 
omissions on the hotline generates corrective action reports, which gets 
them fixed.  I will check to see where we are.

Austin

Austin, 

Where did you get your incredible attitude?  I normally refrain from
posting about your mildly offensive posts, but when you call others on
the carpet like this it is just too much.  

Your sarcasm added *nothing* to your message.  It simply made you look
silly and as you said, "weak".  

"Wow.  Sooooo much current!" 

REALLY!  This makes you sound like a 12 year old in the school yard... 
nothing entertaining about that! 

Your posts are normally useful and informative.  Just leave the attitude
out of it, ok? 


Austin Lesea wrote:
> 
> Brian,
> 
> I would appreciate it if you did detail every single omission,
> distortion, or mis-representation.
> 
> In fact, I demand it, or an apology.  As you know, when I make a
> mistake, I own up to it immediately.  I expect no less from others.
> 
> To say "if you are already drawing no power, then 200 mW is a lot of
> power" is a pretty inane response.
> 
> Obviously.  Your point?
> 
> Peter's comment is perfectly accurate:  series terminations dissipate
> virtually no power in the series termination resistors.
> 
> As for my sarcasm, although sarcasm is known as the "weapon of the
> weak." it does serve a purpose to emphasize a point.  I reserve the
> right to be as entertaining as possible.
> 
> Thanks for the suggestion of turning the reference resistors off.  Not a
> bad idea at all.
> 
> Power estimation tools lag the rest of the tools.  Entering in the
> omissions on the hotline generates corrective action reports, which gets
> them fixed.  I will check to see where we are.
> 
> Austin

-- 

Rick "rickman" Collins

rick.collins@XYarius.com
Ignore the reply address. To email me use the above address with the XY
removed.

Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design      URL http://www.arius.com
4 King Ave                               301-682-7772 Voice
Frederick, MD 21701-3110                 301-682-7666 FAX

Rick,

Bad sleepless night.  But really, I was offended by the silly response, 
talking about applications that have 'no power' where DCI is all of the 
power.

Let's face it, I can create any example I want (the part is programmable 
after all).

So I can 'prove' that any current is either a major issue, and can not 
be tolerated whatsoever, or than it is totally insignificant.

That was the point of my 'school yard' comment.

Sorry to have offended you.

I have so many friends out there, I was actually surprised when no one 
called me on that one.....they call me on just about everything else!

Austin

Austin Lesea wrote:
> 
> Rick,
> 
> Bad sleepless night.  But really, I was offended by the silly response,
> talking about applications that have 'no power' where DCI is all of the
> power.
> 
> Let's face it, I can create any example I want (the part is programmable
> after all).
> 
> So I can 'prove' that any current is either a major issue, and can not
> be tolerated whatsoever, or than it is totally insignificant.
> 
> That was the point of my 'school yard' comment.
> 
> Sorry to have offended you.
> 
> I have so many friends out there, I was actually surprised when no one
> called me on that one.....they call me on just about everything else!

At least you realized that you were going off a bit.  The bad ones think
they are totally justified.  :)

-- 

Rick "rickman" Collins

rick.collins@XYarius.com
Ignore the reply address. To email me use the above address with the XY
removed.

Arius - A Signal Processing Solutions Company
Specializing in DSP and FPGA design      URL http://www.arius.com
4 King Ave                               301-682-7772 Voice
Frederick, MD 21701-3110                 301-682-7666 FAX

Rick,

I am really so easy.  I recognized a long time ago that most engineers 
are insufferable prima donnas, with egos that encompass small planetary 
systems....

Thus, if I can not nurture my idiosyncracies, I would not have any 
personality at all....

Austin

rickman wrote:
> Austin Lesea wrote:
> 
>>Rick,
>>
>>Bad sleepless night.  But really, I was offended by the silly response,
>>talking about applications that have 'no power' where DCI is all of the
>>power.
>>
>>Let's face it, I can create any example I want (the part is programmable
>>after all).
>>
>>So I can 'prove' that any current is either a major issue, and can not
>>be tolerated whatsoever, or than it is totally insignificant.
>>
>>That was the point of my 'school yard' comment.
>>
>>Sorry to have offended you.
>>
>>I have so many friends out there, I was actually surprised when no one
>>called me on that one.....they call me on just about everything else!
> 
> 
> At least you realized that you were going off a bit.  The bad ones think
> they are totally justified.  :)
> 

( reposting this, as the first try never showed up )

Austin,

Responding slightly out of order:
>
> It is always preferable to provide the customer with solutions
> that involve changing bits,
>
  It's much more preferable to provide the customer with a DCI
adjustment circuit which doesn't glitch the impedance so much
when updating, and require years of subsequent BitGen tweaking.

  You even said as much yourself, over on this thread in 2001:

    http://www.fpga-faq.com/archives/28575.html#28576

  Wherein you stated that the magnitude of the DCI impedance 
updates was insignificant.

  In that same thread, you also suggested that there was only
a 25mW power hit for each VRP/VRN pair:

    http://www.fpga-faq.com/archives/28500.html#28510

 Would you care to update either of those claims for Virtex2 ?

>
>I would appreciate it if you did detail every single omission, 
>distortion, or mis-representation.
>
 Coming soon to a newsgroup near you...

>
>In fact, I demand it, or an apology.
>
 The only apologies due here are:

  - from Xilinx, to its' customers, for failing to properly
   document the plethora of Virtex2 DCI HW and SW problems,
   now at 3.5 years after V2 product launch and counting.

  - from you, for posting another sarcastic, condescending,
   and disingenuous response to an accurate and level-headed post

>
>> In a small Spartan3 design drawing little current on VCCINT,
>>power consumption would be dominated by "sooooo much current",
>>especially if using 33 ohm VRP/N resistors as you suggested
>>earlier in the thread.
>
>To say "if you are already drawing no power, then 200 mW is
> a lot of power" is a pretty inane response.
>
   Inane, huh? I found my original sentence quite pithy when
 contrasted to your three paragraph "Nobody cares about 2 W 
 per chip" denial.

   Just how much power do you think a <50 MHz 3S50 design 
 will be drawing on VCCINT ?

   Or, perhaps that was some other FPGA company starting with "X"
 that just announced a low power Spartan3 ???

>
>Peter's comment is perfectly accurate:  series terminations dissipate 
>virtually no power in the series termination resistors.
>
  And what, pray tell, does that have to do with my statement:

    'Peter's claim of "zero additional system power" was inaccurate'
 
  In Austin's world, has the term "system power" been explicitly 
 redefined to exclude per-bank DCI overhead?
 

Brian

Austin Lesea wrote:

> LVDCI_33 is 60 mA for the reference resistors.  For the whole bank.

> Wow.  Sooooo much current!  Face it:  setting the reference for the 
> entire bank does take some power (in this case 3.3V X 60 mA or 200 
> milliwatts.  I am pretty sure this is not going to "break the bank."

(snip)

See:

http://www.world-academy-of-science.org/IMCSE2004/ws/keynote

He has a challenge to build computers using one millionth of
the power of current systems, so maybe 100 microwatts.

On that scale, 200mW does break the bank.

There are people interested in micropower logic.

-- glen

Glen,

I'm impressed.  A million to one reduction in current?

Did anyone hear how he accomplished this miracle?

Austin


> 
> He has a challenge to build computers using one millionth of
> the power of current systems, so maybe 100 microwatts.
> 
> On that scale, 200mW does break the bank.
> 
> There are people interested in micropower logic.
> 
> -- glen
> 
> 

Modern high-performance sub-150 nm conventional CMOS technology has leakage
currents that make that goal unattainable (by a long shot).
Such a  requirement is not mainstream...
Peter Alfke
============================
>
> 
> See:
> 
> http://www.world-academy-of-science.org/IMCSE2004/ws/keynote
> 
> He has a challenge to build computers using one millionth of
> the power of current systems, so maybe 100 microwatts.
> 
> On that scale, 200mW does break the bank.
> 
> There are people interested in micropower logic.
> 
> -- glen
> 
>