Maker Pro
Maker Pro

Survey: FPGA PCB layout

K

krw

Jan 1, 1970
0
Private companies generally offer zilch in retirement benefits. Those
days are long gone.

I don't know about "gone". The age of the "defined benefit" is
pretty much gone in private industry but several still have "defined
contribution" plans. Now, 401Ks make up for a lot of what's been
lost and are portable.
A 70 year old programmer can be better than a 40 year old. At least
that's my impression when I see all the "modern" bloatware ;-)

Maybe. There are better things to do at 70, though. ;-)
Or you just have to have the right connections to make that happen ...

Anyhow, why should retirement checks be based on the last year of
service? IMHO that's wrong. For everyone else it sure doesn't work that way.

The last years' is indicative of the final salary. Most "defined
benefit" plans do take the last year, or last couple of years into
account. What most private pensions *don't* do, that public plans
do is include overtime in the formula. It's not hard to double
one's income for a couple of years. There is no way the tax payer
should pay that forever.
 
J

Joerg

Jan 1, 1970
0
krw said:
I don't know about "gone". The age of the "defined benefit" is
pretty much gone in private industry but several still have "defined
contribution" plans. Now, 401Ks make up for a lot of what's been
lost and are portable.

Sure, but 401(k) is generally funded by the employee. Occasionally the
company throws in a little extra but that is mostly a mere drop in the
bucket in contrast to the lavish pension plans that cover many state
workers.

Maybe. There are better things to do at 70, though. ;-)


Yes, definitely. OTOH completely quitting a career has brought many fine
engineers into the grave within less than a year. My father who worked
as a data processing engineer continued as a consultant and gradually
tapered it off. He said that there was a rash of unexpected deaths of
otherwise quite healthy colleagues right after retirement, and it was
among the group of engineers who shut their careers down more or less
overnight after the first retirement check arrived.

The last years' is indicative of the final salary. Most "defined
benefit" plans do take the last year, or last couple of years into
account. What most private pensions *don't* do, that public plans
do is include overtime in the formula. It's not hard to double
one's income for a couple of years. There is no way the tax payer
should pay that forever.

But it's happening. And we are all paying for that.
 
K

krw

Jan 1, 1970
0
Sure, but 401(k) is generally funded by the employee. Occasionally the
company throws in a little extra but that is mostly a mere drop in the
bucket in contrast to the lavish pension plans that cover many state
workers.

It's quite normal for a company to add significantly to the 401K,
sometimes with strings attached, sometimes without. My PPOE had a
fairly decent 401K (in addition to pension plans for everyone
joining before '06, or so). They matched 1:1 up to 6% of salary
(plus bonusus) and had no management fees for the normal funds. I
understand it's gotten better since they've dropped the pension
plans for the newbs.
Yes, definitely. OTOH completely quitting a career has brought many fine
engineers into the grave within less than a year. My father who worked
as a data processing engineer continued as a consultant and gradually
tapered it off. He said that there was a rash of unexpected deaths of
otherwise quite healthy colleagues right after retirement, and it was
among the group of engineers who shut their careers down more or less
overnight after the first retirement check arrived.

I got quite bored, once I wasn't allowed to make messes at home
anymore. Good thing that only lasted a week or two. ;-)
But it's happening. And we are all paying for that.

Precisely. It's not going to get better. The government requires
others to have fully funded retirement plans, but would have none of
it for themselves.
 
J

Joerg

Jan 1, 1970
0
Nico said:
No. Those (and simple logic) have very few pins.

Ok, then you'd have to modify your statement "always" :)

Am I the nitpicker or what?
 
J

Joerg

Jan 1, 1970
0
John said:
Nico said:
Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.
I start thinking about how the PCB should be routed the minute I start
to draw a schematic. I always draw components with their actual
pin-outs. This helps to group pins together and it helps to
troubleshoot the circuit when the prototype is on your bench (no need
to lookup the pinouts because they are in your diagram).
For quad opamps like the LM324 as well? That can make a schematic harder
to read and will also cause a nightmare if the layouter wants to swap
amp A with amp C and stuff like that.

[...]

A quad opamp doesn't have 1738 pins!

Well, yes, I was just wondering about whether Nico really always draws
the physical package. Looks like he doesn't for smaller stuff.

With 1738 pins you can only hope that the FPGA has enough routing
resources. That used to be a major pain in the early 90's. Don't know
about nowadays since other guys design the parts with the big FPGAs. And
I am glad I don't have to deal with BGA, at least not with large ones ...
 
K

krw

Jan 1, 1970
0
John said:
Nico Coesel wrote:

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.
I start thinking about how the PCB should be routed the minute I start
to draw a schematic. I always draw components with their actual
pin-outs. This helps to group pins together and it helps to
troubleshoot the circuit when the prototype is on your bench (no need
to lookup the pinouts because they are in your diagram).

For quad opamps like the LM324 as well? That can make a schematic harder
to read and will also cause a nightmare if the layouter wants to swap
amp A with amp C and stuff like that.

[...]

A quad opamp doesn't have 1738 pins!

Well, yes, I was just wondering about whether Nico really always draws
the physical package. Looks like he doesn't for smaller stuff.

With 1738 pins you can only hope that the FPGA has enough routing
resources. That used to be a major pain in the early 90's. Don't know
about nowadays since other guys design the parts with the big FPGAs. And

I had a *lot* of routing problems with the SpartanXL series. I had
lotsa logic left but if it would route it would take days. I didn't
have any problems, at the time, with Virtex or Vertex-E. Now the
Virtex-2s and 4s route in a small number of minutes with no errors.
I am glad I don't have to deal with BGA, at least not with large ones ...

I don't deal with them either. That's the layouter's job. ;-)
Actually, right now I just work on what goes into them (though I had
to completely redesign a badly screwed up board in December, which
we *still* don't have back).
 
J

Joerg

Jan 1, 1970
0
John said:
John said:
On Sat, 19 Apr 2008 14:17:44 -0700, Joerg

Nico Coesel wrote:

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.
I start thinking about how the PCB should be routed the minute I start
to draw a schematic. I always draw components with their actual
pin-outs. This helps to group pins together and it helps to
troubleshoot the circuit when the prototype is on your bench (no need
to lookup the pinouts because they are in your diagram).

For quad opamps like the LM324 as well? That can make a schematic harder
to read and will also cause a nightmare if the layouter wants to swap
amp A with amp C and stuff like that.

[...]
A quad opamp doesn't have 1738 pins!
Well, yes, I was just wondering about whether Nico really always draws
the physical package. Looks like he doesn't for smaller stuff.

With 1738 pins you can only hope that the FPGA has enough routing
resources. That used to be a major pain in the early 90's. Don't know
about nowadays since other guys design the parts with the big FPGAs. And
I am glad I don't have to deal with BGA, at least not with large ones ...

The biggest ones we use are Sparten 3's with 456 balls on 1 mm
centers. We haven't had any routing problems so far, doing pretty
complex stuff at 128 MHz clock rates. Our in-house BGA soldering
yield, to date, is exactly 100%. BGAs seem to be a lot easier to
solder reliably than fine-pitch leaded parts. Easier to inspect, too,
since you can't inspect them at all.

The latter is a concern in my field (medical). We need to be able to
inspect. The other concern is involuntary board flexing. Most of my
designs have to sustain under tortures such as freighter pilots
ploughing through a storm in the Carribean in airplanes as old as a DC-3
or a trucker in Africa who is lead-footing it over a few hundred miles
of washboard road.
 
K

krw

Jan 1, 1970
0
John said:
John Larkin wrote:
On Sat, 19 Apr 2008 14:17:44 -0700, Joerg

Nico Coesel wrote:

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.
I start thinking about how the PCB should be routed the minute I start
to draw a schematic. I always draw components with their actual
pin-outs. This helps to group pins together and it helps to
troubleshoot the circuit when the prototype is on your bench (no need
to lookup the pinouts because they are in your diagram).

For quad opamps like the LM324 as well? That can make a schematic harder
to read and will also cause a nightmare if the layouter wants to swap
amp A with amp C and stuff like that.

[...]
A quad opamp doesn't have 1738 pins!

Well, yes, I was just wondering about whether Nico really always draws
the physical package. Looks like he doesn't for smaller stuff.

With 1738 pins you can only hope that the FPGA has enough routing
resources. That used to be a major pain in the early 90's. Don't know
about nowadays since other guys design the parts with the big FPGAs. And
I am glad I don't have to deal with BGA, at least not with large ones ...

The biggest ones we use are Sparten 3's with 456 balls on 1 mm
centers. We haven't had any routing problems so far, doing pretty
complex stuff at 128 MHz clock rates. Our in-house BGA soldering
yield, to date, is exactly 100%. BGAs seem to be a lot easier to
solder reliably than fine-pitch leaded parts. Easier to inspect, too,
since you can't inspect them at all.

The latter is a concern in my field (medical). We need to be able to
inspect. The other concern is involuntary board flexing. Most of my
designs have to sustain under tortures such as freighter pilots
ploughing through a storm in the Carribean in airplanes as old as a DC-3
or a trucker in Africa who is lead-footing it over a few hundred miles
of washboard road.
X-Rays?
 
R

rickman

Jan 1, 1970
0
No reason to live if you have nothing to do. :(

--http://improve-usenet.org/index.html

Use any search engine other than Google till they stop polluting USENET
with porn and junk commercial SPAM

If you have broadband, your ISP may have a NNTP news server included in
your account:http://www.usenettools.net/ISP.htm

I used to use a newsreader with the servers at RCN. But I can't get
the reader to find the servers anymore. Actually, it seems to be an
account validation thing and dealing with RCN support is such a pain
that I am willing to put up with the SPAM until it becomes
unbearable. When that happens I will do without newsgroups. A lot of
the important stuff is handled in highly targeted forums anyway. I
mainly come here to see what others are doing and having problems with
and to ask an occasional question. I seem to recall that a question I
asked a month or so ago resulted in a lot of crap being thrown
around. That is almost as bad as the SPAM and no ISP can filter it!
 
J

Joerg

Jan 1, 1970
0
krw said:
John said:
On Sun, 20 Apr 2008 14:13:21 -0700, Joerg

John Larkin wrote:
On Sat, 19 Apr 2008 14:17:44 -0700, Joerg

Nico Coesel wrote:

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.
I start thinking about how the PCB should be routed the minute I start
to draw a schematic. I always draw components with their actual
pin-outs. This helps to group pins together and it helps to
troubleshoot the circuit when the prototype is on your bench (no need
to lookup the pinouts because they are in your diagram).

For quad opamps like the LM324 as well? That can make a schematic harder
to read and will also cause a nightmare if the layouter wants to swap
amp A with amp C and stuff like that.

[...]
A quad opamp doesn't have 1738 pins!

Well, yes, I was just wondering about whether Nico really always draws
the physical package. Looks like he doesn't for smaller stuff.

With 1738 pins you can only hope that the FPGA has enough routing
resources. That used to be a major pain in the early 90's. Don't know
about nowadays since other guys design the parts with the big FPGAs. And
I am glad I don't have to deal with BGA, at least not with large ones ...
The biggest ones we use are Sparten 3's with 456 balls on 1 mm
centers. We haven't had any routing problems so far, doing pretty
complex stuff at 128 MHz clock rates. Our in-house BGA soldering
yield, to date, is exactly 100%. BGAs seem to be a lot easier to
solder reliably than fine-pitch leaded parts. Easier to inspect, too,
since you can't inspect them at all.
The latter is a concern in my field (medical). We need to be able to
inspect. The other concern is involuntary board flexing. Most of my
designs have to sustain under tortures such as freighter pilots
ploughing through a storm in the Carribean in airplanes as old as a DC-3
or a trucker in Africa who is lead-footing it over a few hundred miles
of washboard road.
X-Rays?

They tend not to penetrate through metal so well and are frowned upon at
the work place.
 
R

rickman

Jan 1, 1970
0
John Larkin wrote:

No reason to live if you have nothing to do. :(

--http://improve-usenet.org/index.html

Use any search engine other than Google till they stop polluting USENET
with porn and junk commercial SPAM

If you have broadband, your ISP may have a NNTP news server included in
your account:http://www.usenettools.net/ISP.htm


What is the point of including a link to the "improve usenet" page? I
don't see any useful information there. The page complains about a
few things and offers no advice on what to do about any of it...
counter to its stated purpose of being "an attempt to make Usenet
participation a better experience for those who are clued as to what
the Usenet medium is and how to use it". Instead of offering anything
constructive, they even insult people that they should be trying to
reach and convince... "most of the people who post to Usenet via the
clunky Google Groups web interface are lusers or lamers".

Do you think that this page has had any sort of positive influence on
usenet? Does your posting the link help in any way?
 
J

Joerg

Jan 1, 1970
0
Joel said:
Hi Joerg,



Actually I think a very significant fraction of companies (at least those
hiring EEs) offer some sort of contribution to 401k plans, sometimes profit
sharing, sometimes stock options, etc... but I concur that the old days of
"company pensions" is pretty much gone.

Mostly it's a mere pittance. And that's ok, I am a strong believer that
everyone should pull their own weight. Except disabled people, of course.

Absolutely, but if you're an employer it's definitely a legitimate
consideration that starting a bunch of 70-year-olds on a, say, decade-long
"modernization" project is rather riskier than if you toss a few 50- or
30-year-olds into the mix as well. :)

True. However, we should embrace the Japanese concept of letting older
folks teach the young ones, not lay them off.

I agree that one year seems too short, but trying to figure out how many years
should be taken into consideration (which is effectively what happens in
private companies if the company is contributing to your 401k) is not going to
be easy either.

Just make it the same as with 401(k), IRA, old style pension funds,
social security etc. What counts is what you pay in over your whole career.

We can read such stories almost daily, just an example from this morning:
http://www.sacbee.com/111/story/876845.html

Guess who gets to pay the tab for the agency's legal defense?
 
J

Joerg

Jan 1, 1970
0
John said:
My company contributes 15% of employee salaries (including bonuses) to
their 401K. It's tax deductable to the company, not taxable to the
employees, and makes everybody happy. That's what really matters,
after all.

Yes, but all along I've had the impression that your company does a lot
more for emplyee motivation than most others. 15% is huge.

But it's not a pension, in that the company has no obligations at all.

And it shouldn't be. Employees must understand that investing it is
their responsibility, not yours.
 
K

krw

Jan 1, 1970
0
krw said:
John Larkin wrote:
On Sun, 20 Apr 2008 14:13:21 -0700, Joerg

John Larkin wrote:
On Sat, 19 Apr 2008 14:17:44 -0700, Joerg

Nico Coesel wrote:

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.
I start thinking about how the PCB should be routed the minute I start
to draw a schematic. I always draw components with their actual
pin-outs. This helps to group pins together and it helps to
troubleshoot the circuit when the prototype is on your bench (no need
to lookup the pinouts because they are in your diagram).

For quad opamps like the LM324 as well? That can make a schematic harder
to read and will also cause a nightmare if the layouter wants to swap
amp A with amp C and stuff like that.

[...]
A quad opamp doesn't have 1738 pins!

Well, yes, I was just wondering about whether Nico really always draws
the physical package. Looks like he doesn't for smaller stuff.

With 1738 pins you can only hope that the FPGA has enough routing
resources. That used to be a major pain in the early 90's. Don't know
about nowadays since other guys design the parts with the big FPGAs. And
I am glad I don't have to deal with BGA, at least not with large ones ...
The biggest ones we use are Sparten 3's with 456 balls on 1 mm
centers. We haven't had any routing problems so far, doing pretty
complex stuff at 128 MHz clock rates. Our in-house BGA soldering
yield, to date, is exactly 100%. BGAs seem to be a lot easier to
solder reliably than fine-pitch leaded parts. Easier to inspect, too,
since you can't inspect them at all.

The latter is a concern in my field (medical). We need to be able to
inspect. The other concern is involuntary board flexing. Most of my
designs have to sustain under tortures such as freighter pilots
ploughing through a storm in the Carribean in airplanes as old as a DC-3
or a trucker in Africa who is lead-footing it over a few hundred miles
of washboard road.
X-Rays?

They tend not to penetrate through metal so well and are frowned upon at
the work place.

But that's how it's done.
 
K

krw

Jan 1, 1970
0
Yes, but that's expensive and it's not usually done on a production
basis. We do have a video prism thing the lets us peek under the chip,
with fair visibility three or maybe four balls in. But we don't
routinely use it. The BGAs just work.

Right. Flip-chip mounting of chips to substrates has been done for
at least forty years. It just works.
 
J

Joerg

Jan 1, 1970
0
krw said:
krw said:
John Larkin wrote:
On Sun, 20 Apr 2008 14:13:21 -0700, Joerg

John Larkin wrote:
On Sat, 19 Apr 2008 14:17:44 -0700, Joerg

Nico Coesel wrote:

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.
I start thinking about how the PCB should be routed the minute I start
to draw a schematic. I always draw components with their actual
pin-outs. This helps to group pins together and it helps to
troubleshoot the circuit when the prototype is on your bench (no need
to lookup the pinouts because they are in your diagram).

For quad opamps like the LM324 as well? That can make a schematic harder
to read and will also cause a nightmare if the layouter wants to swap
amp A with amp C and stuff like that.

[...]
A quad opamp doesn't have 1738 pins!

Well, yes, I was just wondering about whether Nico really always draws
the physical package. Looks like he doesn't for smaller stuff.

With 1738 pins you can only hope that the FPGA has enough routing
resources. That used to be a major pain in the early 90's. Don't know
about nowadays since other guys design the parts with the big FPGAs. And
I am glad I don't have to deal with BGA, at least not with large ones ...
The biggest ones we use are Sparten 3's with 456 balls on 1 mm
centers. We haven't had any routing problems so far, doing pretty
complex stuff at 128 MHz clock rates. Our in-house BGA soldering
yield, to date, is exactly 100%. BGAs seem to be a lot easier to
solder reliably than fine-pitch leaded parts. Easier to inspect, too,
since you can't inspect them at all.

The latter is a concern in my field (medical). We need to be able to
inspect. The other concern is involuntary board flexing. Most of my
designs have to sustain under tortures such as freighter pilots
ploughing through a storm in the Carribean in airplanes as old as a DC-3
or a trucker in Africa who is lead-footing it over a few hundred miles
of washboard road.

X-Rays?
They tend not to penetrate through metal so well and are frowned upon at
the work place.

But that's how it's done.

Well, what else can they do? And I guess OSHA is going to be breathing
down their backs all the time. I like to see things so I prefer QFP. of
course you won't get 1700 pins that way but usually that's not realy needed.
 
J

Joerg

Jan 1, 1970
0
krw said:
Right. Flip-chip mounting of chips to substrates has been done for
at least forty years. It just works.

Yes, and I've done my fair share as well. But: It was either to a hard
substrate that does not flex such as alumina or to a very flexible
material such as Kapton. FR4 ain't my kind of turf with BGA. Can be ok
for gear that doesn't get stressed much but not in my field of work.
 
K

krw

Jan 1, 1970
0
krw said:
krw wrote:
John Larkin wrote:
On Sun, 20 Apr 2008 14:13:21 -0700, Joerg

John Larkin wrote:
On Sat, 19 Apr 2008 14:17:44 -0700, Joerg

Nico Coesel wrote:

Does anybody out there have a good methodology for determining your
optimal FPGA pinouts, for making PCB layouts nice, pretty, and clean?
The brute force method is fairly maddening. I'd be curious to hear if
anybody has any 'tricks of the trade' here.
I start thinking about how the PCB should be routed the minute I start
to draw a schematic. I always draw components with their actual
pin-outs. This helps to group pins together and it helps to
troubleshoot the circuit when the prototype is on your bench (no need
to lookup the pinouts because they are in your diagram).

For quad opamps like the LM324 as well? That can make a schematic harder
to read and will also cause a nightmare if the layouter wants to swap
amp A with amp C and stuff like that.

[...]
A quad opamp doesn't have 1738 pins!

Well, yes, I was just wondering about whether Nico really always draws
the physical package. Looks like he doesn't for smaller stuff.

With 1738 pins you can only hope that the FPGA has enough routing
resources. That used to be a major pain in the early 90's. Don't know
about nowadays since other guys design the parts with the big FPGAs. And
I am glad I don't have to deal with BGA, at least not with large ones ...
The biggest ones we use are Sparten 3's with 456 balls on 1 mm
centers. We haven't had any routing problems so far, doing pretty
complex stuff at 128 MHz clock rates. Our in-house BGA soldering
yield, to date, is exactly 100%. BGAs seem to be a lot easier to
solder reliably than fine-pitch leaded parts. Easier to inspect, too,
since you can't inspect them at all.

The latter is a concern in my field (medical). We need to be able to
inspect. The other concern is involuntary board flexing. Most of my
designs have to sustain under tortures such as freighter pilots
ploughing through a storm in the Carribean in airplanes as old as a DC-3
or a trucker in Africa who is lead-footing it over a few hundred miles
of washboard road.

X-Rays?

They tend not to penetrate through metal so well and are frowned upon at
the work place.

But that's how it's done.

Well, what else can they do? And I guess OSHA is going to be breathing
down their backs all the time. I like to see things so I prefer QFP. of
course you won't get 1700 pins that way but usually that's not realy needed.

Your "usually" and mine are quite different. ;-)
 
K

krw

Jan 1, 1970
0
Yes, and I've done my fair share as well. But: It was either to a hard
substrate that does not flex such as alumina or to a very flexible
material such as Kapton. FR4 ain't my kind of turf with BGA. Can be ok
for gear that doesn't get stressed much but not in my field of work.

They've been flip-chip mounting on organic substrates for at least a
decade, too.
 
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