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Messages from 157525

Article: 157525
Subject: Re: Using FPGA to feed 80386
From: rickman <gnuarm@gmail.com>
Date: Sun, 14 Dec 2014 23:37:12 -0500
Links: << >>  << T >>  << A >>
On 12/14/2014 7:50 PM, Rick C. Hodgin wrote:
> Even better:
>
>      http://m.youtube.com/#/watch?v=4SNkzoOvoD8

https://www.youtube.com/watch?v=lxRNQbEGwm4

-- 

Rick

Article: 157526
Subject: Re: Using FPGA to feed 80386
From: rickman <gnuarm@gmail.com>
Date: Sun, 14 Dec 2014 23:43:59 -0500
Links: << >>  << T >>  << A >>
On 12/14/2014 10:59 PM, Rick C. Hodgin wrote:
> Rickman wrote:
>> ...because there is no solder resist and shorts
>> are very hard to prevent.
>
> A simultaneous parallel laser could burn thru
> a transparency to provide the solder mask.
>
> An assembly line could even be created to run
> them N-off in assembled form. Automated
> deposition of solder paste, physical IC packages,
> run through an oven, cooldown and testing.
>
> It could all be done in a year from idea to
> production.

Hmmmmm.... or they could make them the way they do now and save the 
year!  :)

I was asking how *you* would do it at home...

-- 

Rick

Article: 157527
Subject: Re: Using FPGA to feed 80386
From: rickman <gnuarm@gmail.com>
Date: Sun, 14 Dec 2014 23:45:57 -0500
Links: << >>  << T >>  << A >>
On 12/14/2014 11:25 PM, Rick C. Hodgin wrote:
> I found these chips available for $10 each. 3.3V
> fully static, 16-bit data bus.
>
>      http://www.findchips.com/search/ng80386sxl-33
>
> I am considering them.

Considering them for what?  Are you planning to build something?

-- 

Rick

Article: 157528
Subject: Re: Using FPGA to feed 80386
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Sun, 14 Dec 2014 20:48:57 -0800 (PST)
Links: << >>  << T >>  << A >>
rickman wrote:
> I was asking how *you* would do it at home...

Use an online service to get finished boards and
solder masks. :-)

If I had money to do so, I would move into this
area of profession. Reminds me of welding (you
create physical things rather than intangible
things as with software).

Best regards,
Rick C. Hodgin

Article: 157529
Subject: Re: Using FPGA to feed 80386
From: rickman <gnuarm@gmail.com>
Date: Mon, 15 Dec 2014 00:02:39 -0500
Links: << >>  << T >>  << A >>
On 12/14/2014 11:48 PM, Rick C. Hodgin wrote:
> rickman wrote:
>> I was asking how *you* would do it at home...
>
> Use an online service to get finished boards and
> solder masks. :-)
>
> If I had money to do so, I would move into this
> area of profession. Reminds me of welding (you
> create physical things rather than intangible
> things as with software).

I expect it does take a bunch of money to make boards.  The equipment is 
rather expensive.  But doing the design can be fairly inexpensive still. 
  It's the debug that requires expensive equipment.  Scopes and such can 
rack up big bucks.

-- 

Rick

Article: 157530
Subject: Re: Using FPGA to feed 80386
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Sun, 14 Dec 2014 21:22:27 -0800 (PST)
Links: << >>  << T >>  << A >>
ricknman wrote:
> Scopes and such can rack up big bucks.

I do have an oscilloscope. Got it in 1996. :-)

Best regards,
Rick C. Hodgin

Article: 157531
Subject: Re: Using FPGA to feed 80386
From: Tom Gardner <spamjunk@blueyonder.co.uk>
Date: Mon, 15 Dec 2014 12:55:26 +0000
Links: << >>  << T >>  << A >>
On 15/12/14 00:50, Rick C. Hodgin wrote:
> Even better:
>
>      http://m.youtube.com/#/watch?v=4SNkzoOvoD8

Using high-power lasers which aren't fully enclosed is a recipe for
blinding an innocent passer-by. Specular reflections can be unexpected
and dangerous.

Saying "oops, sorry" just isn't enough when that happens.

I don't care what someone does to their own eyes. I do care what
they (might) do to other people's eyes.


Article: 157532
Subject: Re: Using FPGA to feed 80386
From: Tom Gardner <spamjunk@blueyonder.co.uk>
Date: Mon, 15 Dec 2014 13:11:04 +0000
Links: << >>  << T >>  << A >>
On 15/12/14 05:02, rickman wrote:
> On 12/14/2014 11:48 PM, Rick C. Hodgin wrote:
>> rickman wrote:
>>> I was asking how *you* would do it at home...
>>
>> Use an online service to get finished boards and
>> solder masks. :-)
>>
>> If I had money to do so, I would move into this
>> area of profession. Reminds me of welding (you
>> create physical things rather than intangible
>> things as with software).
>
> I expect it does take a bunch of money to make boards.

Remarkably little, nowadays. So much so that it really is questionable
whether it is worth doing them at home. IMHSHO, the main reasons would
be "to see if I can" and "if I need it today".

Low end example: 10cm*10cm double sided, plated through holes, solder
mask, silkscreen. Cost $25 for 10 boards. (4 layer $50)
http://dirtypcbs.com/

Controlled impedance example: 10cm*10cm 4 layer 100 for 2 boards.
6 layer 200. Available from many places. Some places also offer
assembly, e.g. http://www.pcbtrain.co.uk/


> The equipment is rather
> expensive.  But doing the design can be fairly inexpensive still.  It's the
> debug that requires expensive equipment.  Scopes and such can rack up big bucks.

Scopes can be had cheaply, especially second hand. High-speed probes typically
cost as much as the scope (>$10k isn't unusual!) Even decent 150MHz passive
probes cost $150.


Article: 157533
Subject: Re: Using FPGA to feed 80386
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Mon, 15 Dec 2014 05:13:08 -0800 (PST)
Links: << >>  << T >>  << A >>
Tom Gardener wrote:
> I don't care what someone does to their own
> eyes. I do care what they (might) do to other
> people's eyes.

In the first video he held up filter glasses so he has some idea of eye protection.

This looks like a prototype being built in his
basement lab.

Best regards,
Rick C. Hodgin

Article: 157534
Subject: Re: Using FPGA to feed 80386
From: Tom Gardner <spamjunk@blueyonder.co.uk>
Date: Mon, 15 Dec 2014 13:18:12 +0000
Links: << >>  << T >>  << A >>
On 15/12/14 04:01, Rick C. Hodgin wrote:
> crisabele wrote:
>> What's your experience designing and
>> building hardware previously?
>
> Minimal. Nearly zero with regards to ICs, and
> zero related to FPGAs.

If you are thinking of designing circuits and building boards
with FPGAs, then here's a couple of test questions. Good answers
are /necessary/ but not /sufficient/.

What is the highest frequency in your design?

When would you choose to use 6 layers rather than 4?

What types of decoupling capacitors would you use, where would
you place them, and how would you connect them?

What shape decoupling capacitor is optimal?

Warning: there's a *lot* of work and understanding required
to get accurate answers to those questions. Poor answers will
result in non-working boards or pattern-sensitive boards.



Article: 157535
Subject: Re: Using FPGA to feed 80386
From: Tom Gardner <spamjunk@blueyonder.co.uk>
Date: Mon, 15 Dec 2014 13:36:30 +0000
Links: << >>  << T >>  << A >>
On 15/12/14 13:13, Rick C. Hodgin wrote:
> Tom Gardener wrote:
>> I don't care what someone does to their own
>> eyes. I do care what they (might) do to other
>> people's eyes.
>
> In the first video he held up filter glasses so he has some idea of eye protection.

Sure; but I don't care about his eyes.

*Did he also give them to passers by,*
*e.g. everyone else in the building?*

Motto from BT Labs, prominently displayed on relevant walls:
"Do not look into laser with remaining eye".
They were /very/ serious about specular reflections.


Article: 157536
Subject: Re: Using FPGA to feed 80386
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Mon, 15 Dec 2014 05:59:05 -0800 (PST)
Links: << >>  << T >>  << A >>
On Monday, December 15, 2014 8:36:34 AM UTC-5, Tom Gardner wrote:
> On 15/12/14 13:13, Rick C. Hodgin wrote:
> > Tom Gardener wrote:
> >> I don't care what someone does to their own
> >> eyes. I do care what they (might) do to other
> >> people's eyes.
> >
> > In the first video he held up filter glasses so he has some idea of eye protection.
> 
> Sure; but I don't care about his eyes.
> 
> *Did he also give them to passers by,*
> *e.g. everyone else in the building?*
> 
> Motto from BT Labs, prominently displayed on relevant walls:
> "Do not look into laser with remaining eye".
> They were /very/ serious about specular reflections.

To me it looks like it's done at his home in his basement.  Perhaps it's
done somewhere else.  Being as it's a prototype, and being particularly
filmed for the video, it makes sense that it's all open.  I'm sure the
final form would offer sufficient protection.

Best regards,
Rick C. Hodgin

Article: 157537
Subject: Re: Using FPGA to feed 80386
From: Tom Gardner <spamjunk@blueyonder.co.uk>
Date: Mon, 15 Dec 2014 14:25:08 +0000
Links: << >>  << T >>  << A >>
On 15/12/14 13:59, Rick C. Hodgin wrote:
> On Monday, December 15, 2014 8:36:34 AM UTC-5, Tom Gardner wrote:
>> On 15/12/14 13:13, Rick C. Hodgin wrote:
>>> Tom Gardener wrote:
>>>> I don't care what someone does to their own
>>>> eyes. I do care what they (might) do to other
>>>> people's eyes.
>>>
>>> In the first video he held up filter glasses so he has some idea of eye protection.
>>
>> Sure; but I don't care about his eyes.
>>
>> *Did he also give them to passers by,*
>> *e.g. everyone else in the building?*
>>
>> Motto from BT Labs, prominently displayed on relevant walls:
>> "Do not look into laser with remaining eye".
>> They were /very/ serious about specular reflections.
>
> To me it looks like it's done at his home in his basement.  Perhaps it's
> done somewhere else.  Being as it's a prototype, and being particularly
> filmed for the video, it makes sense that it's all open.  I'm sure the
> final form would offer sufficient protection.

What makes you think that?

Counterexamples from a 10s google:

https://www.kickstarter.com/projects/1537608281/lazerblade-the-affordable-laser-cutter-engraver
http://mr-beam.org/
https://www.kickstarter.com/projects/820277733/laser-cube
https://www.kickstarter.com/projects/mrbeam/mr-beam-a-portable-laser-cutter-and-engraver-kit
https://www.kickstarter.com/projects/2117384013/flux-all-in-one-3d-printer-unlimited-elegant-simpl

Article: 157538
Subject: Re: Using FPGA to feed 80386
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Mon, 15 Dec 2014 06:29:16 -0800 (PST)
Links: << >>  << T >>  << A >>
On Monday, December 15, 2014 8:18:16 AM UTC-5, Tom Gardner wrote:
> On 15/12/14 04:01, Rick C. Hodgin wrote:
> > crisabele wrote:
> >> What's your experience designing and
> >> building hardware previously?
> >
> > Minimal. Nearly zero with regards to ICs, and
> > zero related to FPGAs.
> 
> If you are thinking of designing circuits and building boards
> with FPGAs, then here's a couple of test questions. Good answers
> are /necessary/ but not /sufficient/.
> 
> What is the highest frequency in your design?

Probably 33 MHz to 40 MHz.

> When would you choose to use 6 layers rather than 4?

I'm guessing:  When you need to isolate analog and digital traffic, or
when your pin counts are sufficiently high that you need access to a
common ground plane that's not closely coupled to the power source.

> What types of decoupling capacitors would you use, where would
> you place them, and how would you connect them?

No idea. :-)  Wherever the people on forums like this tell me to put
them after they review my design.

> What shape decoupling capacitor is optimal?

Corn kernel shape. :-)

> Warning: there's a *lot* of work and understanding required
> to get accurate answers to those questions. Poor answers will
> result in non-working boards or pattern-sensitive boards.

No doubts.  The majority of the things I would do would be fabric
connection, and in many cases, using existing designs which already
have those things figured out, but with different programming in
the FPGA for whatever task I'm pursuing.

Best regards,
Rick C. Hodgin

Article: 157539
Subject: Re: Using FPGA to feed 80386
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Mon, 15 Dec 2014 06:30:52 -0800 (PST)
Links: << >>  << T >>  << A >>
On Monday, December 15, 2014 9:25:12 AM UTC-5, Tom Gardner wrote:
> On 15/12/14 13:59, Rick C. Hodgin wrote:
> > On Monday, December 15, 2014 8:36:34 AM UTC-5, Tom Gardner wrote:
> >> On 15/12/14 13:13, Rick C. Hodgin wrote:
> >>> Tom Gardener wrote:
> >>>> I don't care what someone does to their own
> >>>> eyes. I do care what they (might) do to other
> >>>> people's eyes.
> >>>
> >>> In the first video he held up filter glasses so he has some idea of eye protection.
> >>
> >> Sure; but I don't care about his eyes.
> >>
> >> *Did he also give them to passers by,*
> >> *e.g. everyone else in the building?*
> >>
> >> Motto from BT Labs, prominently displayed on relevant walls:
> >> "Do not look into laser with remaining eye".
> >> They were /very/ serious about specular reflections.
> >
> > To me it looks like it's done at his home in his basement.  Perhaps it's
> > done somewhere else.  Being as it's a prototype, and being particularly
> > filmed for the video, it makes sense that it's all open.  I'm sure the
> > final form would offer sufficient protection.
> 
> What makes you think that?
> 
> Counterexamples from a 10s google:
> 
> https://www.kickstarter.com/projects/1537608281/lazerblade-the-affordable-laser-cutter-engraver
> http://mr-beam.org/
> https://www.kickstarter.com/projects/820277733/laser-cube
> https://www.kickstarter.com/projects/mrbeam/mr-beam-a-portable-laser-cutter-and-engraver-kit
> https://www.kickstarter.com/projects/2117384013/flux-all-in-one-3d-printer-unlimited-elegant-simpl

Because the guy who is developing this laser etcher looks like he has
high skills.  You see the multiple boards, the programming involved,
understanding a great many disciplines and bringing them together.
Plus, on his first video, he shows the filter lenses and posts a splash
screen warning about the dangers of laser light.

Best regards,
Rick C. Hodgin

Article: 157540
Subject: Re: Using FPGA to feed 80386
From: Tom Gardner <spamjunk@blueyonder.co.uk>
Date: Mon, 15 Dec 2014 14:42:21 +0000
Links: << >>  << T >>  << A >>
On 15/12/14 14:30, Rick C. Hodgin wrote:
> Because the guy who is developing this laser etcher looks like he has
> high skills.  You see the multiple boards, the programming involved,
> understanding a great many disciplines and bringing them together.
> Plus, on his first video, he shows the filter lenses and posts a splash
> screen warning about the dangers of laser light.

Sure.

What about the people that make or use such a device?

There are too many ignorant and/or stupid people around.

Article: 157541
Subject: Re: Using FPGA to feed 80386
From: Tom Gardner <spamjunk@blueyonder.co.uk>
Date: Mon, 15 Dec 2014 14:54:55 +0000
Links: << >>  << T >>  << A >>
On 15/12/14 14:29, Rick C. Hodgin wrote:
> On Monday, December 15, 2014 8:18:16 AM UTC-5, Tom Gardner wrote:
>> On 15/12/14 04:01, Rick C. Hodgin wrote:
>>> crisabele wrote:
>>>> What's your experience designing and
>>>> building hardware previously?
>>>
>>> Minimal. Nearly zero with regards to ICs, and
>>> zero related to FPGAs.
>>
>> If you are thinking of designing circuits and building boards
>> with FPGAs, then here's a couple of test questions. Good answers
>> are /necessary/ but not /sufficient/.
>>
>> What is the highest frequency in your design?
>
> Probably 33 MHz to 40 MHz.

Nope. You are probably too low by a factor of *~100*.
Hint: the clock frequency is completely irrelevant.


>> When would you choose to use 6 layers rather than 4?
>
> I'm guessing:  When you need to isolate analog and digital traffic, or
> when your pin counts are sufficiently high that you need access to a
> common ground plane that's not closely coupled to the power source.

Nope, not even close.
Hint: your circuit will have significant energy at GHz frequencies.


>> What types of decoupling capacitors would you use, where would
>> you place them, and how would you connect them?
>
> No idea. :-)  Wherever the people on forums like this tell me to put
> them after they review my design.

You would be advised to read all the manufacturer's app notes.
For example Xilinx, for one family, has UG922 and UG483,
150 pages which are aimed at experienced PCB designers.

I hope by now you are considering buying an FPGA board and
adding your circuit to it as a daughter board or carrier board.
Ensure the connectors are impedance controlled and have good
grounding: many don't.



Article: 157542
Subject: Re: Using FPGA to feed 80386
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Mon, 15 Dec 2014 07:38:50 -0800 (PST)
Links: << >>  << T >>  << A >>
On Monday, December 15, 2014 9:54:58 AM UTC-5, Tom Gardner wrote:
> On 15/12/14 14:29, Rick C. Hodgin wrote:
> > On Monday, December 15, 2014 8:18:16 AM UTC-5, Tom Gardner wrote:
> >> On 15/12/14 04:01, Rick C. Hodgin wrote:
> >>> crisabele wrote:
> >>>> What's your experience designing and
> >>>> building hardware previously?
> >>>
> >>> Minimal. Nearly zero with regards to ICs, and
> >>> zero related to FPGAs.
> >>
> >> If you are thinking of designing circuits and building boards
> >> with FPGAs, then here's a couple of test questions. Good answers
> >> are /necessary/ but not /sufficient/.
> >>
> >> What is the highest frequency in your design?
> >
> > Probably 33 MHz to 40 MHz.
> 
> Nope. You are probably too low by a factor of *~100*.
> Hint: the clock frequency is completely irrelevant.

My project involves building a 386-like CPU.  I do not anticipate it
will run beyond 33 MHz to 40 MHz.

> >> When would you choose to use 6 layers rather than 4?
> >
> > I'm guessing:  When you need to isolate analog and digital traffic, or
> > when your pin counts are sufficiently high that you need access to a
> > common ground plane that's not closely coupled to the power source.
> 
> Nope, not even close.
> Hint: your circuit will have significant energy at GHz frequencies.

I don't intend on running at GHz frequencies.  In fact, I'd like to
ultimately manufacture my CPU on 5,000 nm process technologies as
were used in mid-1980s.

> >> What types of decoupling capacitors would you use, where would
> >> you place them, and how would you connect them?
> >
> > No idea. :-)  Wherever the people on forums like this tell me to put
> > them after they review my design.
> 
> You would be advised to read all the manufacturer's app notes.
> For example Xilinx, for one family, has UG922 and UG483,
> 150 pages which are aimed at experienced PCB designers.
> 
> I hope by now you are considering buying an FPGA board and
> adding your circuit to it as a daughter board or carrier board.
> Ensure the connectors are impedance controlled and have good
> grounding: many don't.

I appreciate your input.  My design plans are to use the Altera FPGA
I've purchased, to connect an Ethernet board I've purchased and get
it running, and then develop from there.  It will be all logic within
the FPGA at first.  That will take time, and during that time I'll be
in a position to ask questions, read, learn, etc.

We'll see though... I am currently iterating through ideas, trying to
figure out how best to serve the Lord with my efforts.

Best regards,
Rick C. Hodgin

Article: 157543
Subject: Re: Using FPGA to feed 80386
From: David Brown <david.brown@hesbynett.no>
Date: Mon, 15 Dec 2014 17:35:37 +0100
Links: << >>  << T >>  << A >>
On 15/12/14 16:38, Rick C. Hodgin wrote:
> On Monday, December 15, 2014 9:54:58 AM UTC-5, Tom Gardner wrote:
>> On 15/12/14 14:29, Rick C. Hodgin wrote:
>>> On Monday, December 15, 2014 8:18:16 AM UTC-5, Tom Gardner wrote:
>>>> On 15/12/14 04:01, Rick C. Hodgin wrote:
>>>>> crisabele wrote:
>>>>>> What's your experience designing and
>>>>>> building hardware previously?
>>>>>
>>>>> Minimal. Nearly zero with regards to ICs, and
>>>>> zero related to FPGAs.
>>>>
>>>> If you are thinking of designing circuits and building boards
>>>> with FPGAs, then here's a couple of test questions. Good answers
>>>> are /necessary/ but not /sufficient/.
>>>>
>>>> What is the highest frequency in your design?
>>>
>>> Probably 33 MHz to 40 MHz.
>>
>> Nope. You are probably too low by a factor of *~100*.
>> Hint: the clock frequency is completely irrelevant.
> 
> My project involves building a 386-like CPU.  I do not anticipate it
> will run beyond 33 MHz to 40 MHz.
> 

Your problem here is that you don't know the basics of designing
schematics or pcbs for FPGAs.  People spend years at university learning
this sort of thing, then years of full-time professional work before
they consider themselves competent.  It is not reasonable to expect that
you can start from scratch and put together a half-decent FPGA board
based on nothing more than hints and advice from a Usenet newsgroup.

A key issue here is that you are thinking about digital hardware, when
in fact this is all high-speed analogue.  Designing /digital/ hardware,
such as the Verilog/VHDL code in the FPGA itself, is pretty simple -
it's all ones and zeros, and if you can get your head around clocking,
flip-flops and latches (and how to avoid them!), and keep to a single
clock domain, then it's not hard to pick up.

But pcb design is analogue.  You think your clock signals switch at 40
MHz, so your maximum frequency is 40 MHz - in fact there are relevant
parts of that signal up to 400 MHz and beyond.  You think your power
lines are at 3.3V (or whatever) - in reality, they vary and contain
significant signals at different frequencies, amplitudes and phases.
You think the 3.3V line is the same across the board, because it is DC -
it will in fact vary in DC and AC components throughout the board, in a
way that can easily be relevant if you get it wrong.  You think that
when a pin drives high or low, the whole signal track goes high or low -
on a fast pcb, the transmission time is relevant, as are reflections as
the signal moves along the track.

I've no doubt that you could learn all this stuff - or at least, learn
as much as you need to know.  But it will take time, and it will take
trial and error - which can become very expensive with FPGA's.  That is
why you are strongly recommended to buy an FPGA board, and limit your
pcb design to daughter boards for it (preferably avoid that too).  Come
back to the fpga pcb board design later when you have the time to spend
on it.





Article: 157544
Subject: Re: Using FPGA to feed 80386
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Mon, 15 Dec 2014 08:45:23 -0800 (PST)
Links: << >>  << T >>  << A >>
I appreciate everyone's advice.  I'll let you know how it turns out.
I'm still filtering ideas about how best to proceed, to use the talents
I possess, and the things I desire to do, in service to the Lord.  I
desire from within to be a good servant, and to not waste my time on
things which are beyond me.  But I also know that in Him, ALL things
are possible, and that He works through communities.  It will never be
me doing any of these projects alone forever.  It will be me doing as
much as I can, and then turning to Him in prayer for help.  If He helps
me I'll proceed.  If not, then I'll move on to the next thing.

It is a servants heart for Him... that is why I proceed on these paths.
I desire to have the foundations be rooted in Him, which is why I'm
looking to 30-year old process technologies and design goals.  These
are likely attainable today without too much trouble.  It will just
take time and collaboration unto Him.

Best regards,
Rick C. Hodgin

Article: 157545
Subject: Re: VHDL Synchronization- two stage FF on all inputs?
From: GaborSzakacs <gabor@alacron.com>
Date: Mon, 15 Dec 2014 18:14:43 -0500
Links: << >>  << T >>  << A >>
rickman wrote:
> On 12/12/2014 5:05 PM, GaborSzakacs wrote:
>> rickman wrote:
>>> On 12/12/2014 2:45 PM, GaborSzakacs wrote:
>>>> rickman wrote:
>>>>> On 12/11/2014 9:08 AM, GaborSzakacs wrote:
>>>>
>>>> [snip]
>>
>>>>
>>>> No.  The second flip-flop has the same sort of metastable window as the
>>>> first.  If the first flop misses that window because the metastability
>>>> was longer, then the second flop will resolve on the following clock
>>>> cycle.  I think you may be under the misapprehension that the 
>>>> metastable
>>>> state means that the first flop is outputing a "1/2" rather that "0"
>>>> or "1" logic level and any sampling during that time would cause
>>>> metastability in the second flop.  In fact that's not the case.
>>>
>>> I don't think that is correct.  A metastable event can create all
>>> sorts of problems on the output including oscillations and
>>> indeterminate levels.  These can produce metastability in the second
>>> stage without having to hit a bullet with a bullet.
>>>
>>>
>>
>> Think again.  A flip-flop has positive feedback gain.  Oscillation
>> is definitely not a possibility.  Somewhere inside the flop you
>> could sit at a threshold voltage for a while, but once you start
>> to resolve, the swing will be monotonic.  The next flop doesn't
>> get fed directly by the node sitting at its threshold, but from
>> a buffered copy.  You'd need a buffer that oscillates when its
>> input sits near a threshold for a nanosecond or two.  You won't
>> find anything like that in an FPGA.
> 
> There is some 40 years of experience and documentation showing the 
> effects of metastability.  Please do a little research on the topic.
> 
Rick,

   If you had even started to look into some of that 40 years of
research, you may have come across a host of articles like this one:

http://webee.technion.ac.il/~ran/papers/Metastability-and-Synchronizers.IEEEDToct2011.pdf

The only mention of oscillation is that it doesn't happen.  At least
not at the output latch node.

Article: 157546
Subject: Re: Using FPGA to feed 80386
From: Tom Gardner <spamjunk@blueyonder.co.uk>
Date: Mon, 15 Dec 2014 23:22:01 +0000
Links: << >>  << T >>  << A >>
On 15/12/14 15:38, Rick C. Hodgin wrote:
> On Monday, December 15, 2014 9:54:58 AM UTC-5, Tom Gardner wrote:
>> On 15/12/14 14:29, Rick C. Hodgin wrote:
>>> On Monday, December 15, 2014 8:18:16 AM UTC-5, Tom Gardner wrote:
>>>> On 15/12/14 04:01, Rick C. Hodgin wrote:
>>>>> crisabele wrote:
>>>>>> What's your experience designing and
>>>>>> building hardware previously?
>>>>>
>>>>> Minimal. Nearly zero with regards to ICs, and
>>>>> zero related to FPGAs.
>>>>
>>>> If you are thinking of designing circuits and building boards
>>>> with FPGAs, then here's a couple of test questions. Good answers
>>>> are /necessary/ but not /sufficient/.
>>>>
>>>> What is the highest frequency in your design?
>>>
>>> Probably 33 MHz to 40 MHz.
>>
>> Nope. You are probably too low by a factor of *~100*.
>> Hint: the clock frequency is completely irrelevant.
>
> My project involves building a 386-like CPU.  I do not anticipate it
> will run beyond 33 MHz to 40 MHz.

You appear to have missed my hint. Here it is again:
THE CLOCK FREQUENCY IS COMPLETELY IRRELEVANT.

If you use a modern FPGA then you *will* have frequencies
in the GHz region. How many GHz depends on the FPGA, IO
standard and drive strength.

Hint: google for risetime and knee frequency.


>>>> When would you choose to use 6 layers rather than 4?
>>>
>>> I'm guessing:  When you need to isolate analog and digital traffic, or
>>> when your pin counts are sufficiently high that you need access to a
>>> common ground plane that's not closely coupled to the power source.
>>
>> Nope, not even close.
>> Hint: your circuit will have significant energy at GHz frequencies.
>
> I don't intend on running at GHz frequencies.  In fact, I'd like to
> ultimately manufacture my CPU on 5,000 nm process technologies as
> were used in mid-1980s.

So what? You *will* have GHz frequencies present.

Even if the max frequency is only 500KHz, you would benefit
from googling for transmission line, ground plane, inductance,
slot, ground bounce in the context of PCBs.


>>>> What types of decoupling capacitors would you use, where would
>>>> you place them, and how would you connect them?
>>>
>>> No idea. :-)  Wherever the people on forums like this tell me to put
>>> them after they review my design.
>>
>> You would be advised to read all the manufacturer's app notes.
>> For example Xilinx, for one family, has UG922 and UG483,
>> 150 pages which are aimed at experienced PCB designers.
>>
>> I hope by now you are considering buying an FPGA board and
>> adding your circuit to it as a daughter board or carrier board.
>> Ensure the connectors are impedance controlled and have good
>> grounding: many don't.
>
> I appreciate your input.  My design plans are to use the Altera FPGA
> I've purchased, to connect an Ethernet board I've purchased and get
> it running, and then develop from there.  It will be all logic within
> the FPGA at first.  That will take time, and during that time I'll be
> in a position to ask questions, read, learn, etc.
>
> We'll see though... I am currently iterating through ideas, trying to
> figure out how best to serve the Lord with my efforts.

Unless you are exceptionally perceptive, you will make several
iterations of that PCB, and unless you understand the cause of
the failures, random iterations/permutations will probably be
ineffective.


Article: 157547
Subject: Re: Using FPGA to feed 80386
From: Tom Gardner <spamjunk@blueyonder.co.uk>
Date: Mon, 15 Dec 2014 23:24:33 +0000
Links: << >>  << T >>  << A >>
On 15/12/14 16:45, Rick C. Hodgin wrote:

> It is a servants heart for Him... that is why I proceed on these paths.
> I desire to have the foundations be rooted in Him, which is why I'm
> looking to 30-year old process technologies and design goals.  These
> are likely attainable today without too much trouble.  It will just
> take time and collaboration unto Him.

Actually you are mixing 30 year old technologies with recent
technologies (modern FPGAs). Guess which puts more stress on
PCB technology?

Article: 157548
Subject: Re: Using FPGA to feed 80386
From: "Rick C. Hodgin" <rick.c.hodgin@gmail.com>
Date: Mon, 15 Dec 2014 15:38:12 -0800 (PST)
Links: << >>  << T >>  << A >>
A focus:
http://biblehub.com/philippians/4-13.htm
"I can do all things through Christ which strengtheneth me."

And a thought to consider:
http://biblehub.com/matthew/12-30.htm
"He that is not with me [Jesus] is against me; and he that gathereth
not with me scattereth abroad."

Have you received the Lord as your personal savior?  If not, I advise
you to learn of Him.  The gospel message (the good news) is that we
need not perish eternally.  Jesus Christ has come to the Earth to make
a way back for us to be restored to God eternally in Heaven.  It is
through His Atonement of sin at the cross.  Because He had no sin, and
because of His Love for us, He took on our sin at the cross and died
with it.  The punishment that was due us was given to Him, so that we
might be made spotless and blameless before God, allowing us to enter
in to Heaven.  Without us receiving His free gift of salvation, our
sin remains upon us, and we must pay the price of our iniquity.

Jesus is the most important person you can ever come to know.  I advise
each of you to seek Him from within, just you and God.  When the TV is
off, when the music is silent, when there are no distractions, listen
to that still, small voice on the inside.  God desires to know you, and
to save you from the punishment due you from your sin.

-----
As for this forum...

I appreciate everyone's advice.  I view a lot of that advice as overt
negativity and down-putting rather than an effort toward helpful
assistance.  As such, I will depart this group now and continue on
in service to the Lord on my own.  In Him there is hope, guidance,
life, and peace.  His is the better place to be as the people who seek
Him look to build each other up, to help each other out, and not cut
each other down.  This is the difference between people who pursue
Jesus Christ, and people who pursue anything else.

Our life has a purpose and a name:  Jesus Christ.

Seek Him, to learn of Him, that He may set you free from the falseness
of this world.  Peace.

Best regards,
Rick C. Hodgin

Article: 157549
Subject: Re: Using FPGA to feed 80386
From: Tim Wescott <seemywebsite@myfooter.really>
Date: Mon, 15 Dec 2014 18:05:52 -0600
Links: << >>  << T >>  << A >>
On Sun, 14 Dec 2014 10:47:45 -0800, Rick C. Hodgin wrote:

> How would I go about making my own boards?
> I am aware of commercial companies which have software you can download,
> and construct the layout through their process manufacturing,
> and you will receive boards and solder masks.
> 
> But are there things you can do yourself? Buy a blank copper layer,
> cover with a photoresist, expose a mask, and then chemically etch away
> the exposed or unexposed are (depending on the resist)?

There is a middle road.

Get a copy of Eagle or KiCad, lay the board out, and get Gerber files.  
Gerber files are universal, unlike the captive software that you're 
talking about.

Then send the Gerber files to a board aggregator (i.e., www.oshpark.com).  
Oshpark charges $5.00 per square inch and sends you three boards, which is 
not a bad price at all.  You'll only get a 2-layer board, which may not be 
enough.  They also do 4-layer, for more money and slower service.

You're definitely diving off the deep end without a life preserver, here 
-- would your experience be more complete if someone tied you up in a bag 
before you jumped into the water?

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com



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