Old analogue scopes beat new digital scopes, for bit-bashed digital outputs

[joeqsmith]

Sorry, read the title then saw it was about Rigol scopes vs some analog relic.  I gave away my old Hitachi analog scope and my newer Lecroy but kept the first one I ever owned, the 7200.   VME chassis, 68K based relic from the USAF's past.   Not exactly what I would consider the high end of the curve.   I would even go so far as to call it a very low end DSO by todays standards, or even my other DSOs.   

I'll have to check the little micro use used.   Rather than go that route, I just programmed my old Sony Arb with your pattern and roughly the same levels.   From the 2nd picture, you will see this is a single shot.   Third picture, turned on the auto measure and RIS with the 4GHz sampler.   

Like I said, it's a relic but I still use it any time I think I may damage something.  I can't think of a time I would have needed an analog scope or an analog handheld meter for that matter.   I do still have my vacuum tube grid dip meter.

I hadn't spotted that you had changed the contents of your posting, adding significant content.

Bear in mind that my whole posting is not related to expensive professional scopes, but is related to the class of cheap scopes frequently and forcefully recommended in this forum - and to what extent they are suitable for bit-bashed digital signals.

What's the 7200's basic spec, particularly the front-end analogue bandwidth? Given that LeCroy is a long-standing decent professional brand, I would hope and expect  that it would perform "without surprises". I don't see any surprises in the second screenshot.

I don't understand what the Arb Generator screenshot is showing, and can't see the waveform it is generating. Certainly 400kHz is much slower than the waveform I generated (bit period 4ns). The voltage levels ought to be irrelevant.

I don't understand what the last screenshot is showing, nor how it relates to the issue I've mentioned.

If you are interested in hard realtime multicore parallel systems, the XMOS processors and xC are definitely worth understanding. Their pedigree (people, theoretical basis, practical experience) dates back to the 70s in the form of CSP, Occam, Links/Channels and the Transputer. Some of the concepts have found a place in very different systems, e.g. some TI DSPs.

Right, I read what you wrote and understood.  Just thought I would inject something in my holding place.   

The Arb screenshot is some crappy app I put together to drive my old Sony.  The waveform is shown in the bottom of the screen. 

Now we come to the fundamental problem.  I had assumed you knew how to read a scope.  You are at 20ns/div.  I also show 20ns/div.  Count the number of cycles per division on my screen shot and what do you see?  Maybe that I am actually running a little faster than you, not slower.   

In your original post you state

The first point to note is that the 80:20 transition times of the output is 1ns (90:10 is 1.8ns).

  The last screen shot shows a rise and fall time (10/90) of 1.3ns.  Those digital readouts must have thrown you off.      Anyway, I wanted you to see that it was in the ballpark (slightly faster edge) than what you show.   

The 7200 is a modular scope.  The 7242B w/50 ohm coupling has an analog BW of 500 MHz.  Looking at the edge rates, I was using the 7262 which has a 4GHz bandwidth, 10 bits vertical and 100GS/s (RIS). 

As I mentioned, I gave away my one Lecroy that was much nicer than this one.   There is no color LCD screen so not much value to the beginner.  I bought the Hitachi brand new and rarely ever used it after I bought this old LeCroy.  The only advantage the Hitachi had was weight and size.

**** Small update ****
Just in case there was some question about how the old relic would handle the 10ns pulses at 10KHz in single shot.  I figure 12ns ish was close enough for you. 

In case you missed it, I also attached a screen capture of what I did to simulate your pattern test. 

[David Hess]

For what its worth, when I was looking to buy an entry level scope analog just wasn't an option.

For a complete beginner buying used equipment of unknown condition is a massive risk.  Not only are you incapable of repairing problems (even simple ones) with the scope, but you don't even feel qualified to judge whether the scope is working properly in the first place.

Used scopes can become pretty pricy outside of the USA, and spending that kind of money just doesn't seem smart when the 1054z exists.

Now when you start looking to buy a second scope many of the used analogs start to become very interesting.

We pretty much agree.

A beginner should only have a working scope, of whatever type. Taking on a "restoration project" is only for those that enjoy doing that and are prepared to take some risks!

If money is a serious consideration, which is likely on this forum, then it may be worth considering a very cheap very basic analogue scope. I don't know where you are based, but in the UK if you are patient you can find working examples at about £1/MHz, and frequently they are simply given away. (My local hackspace will shortly be throwing half a dozen out, unless members want them!)

This is the big problem.  There are lots of good used and inexpensive analog oscilloscopes out there but the people who could make the best use of them do not have the experience to recognize or maintain them.

For this reason, I usually end up recommending the Rigol DS1000Z or similar despite my misgivings unless they have someone who can help them find a less expensive alternative.

And I agree, while there's little point in having two very similar scopes (or tools), it can be worth having significantly different scopes (or tools) - so that you can use the unique advantages of each as appropriate. That's why I also have a new 10MHz (not 100MHz) digitizing storage scope.

Despite being a big believer in this, I still have duplicate oscilloscopes but only because I end up fixing every one of them.

[snoopy]

In this test the program sits in a tight loop outputting a constant pattern (0x005555ff) using an I/O port's SERDES output running as fast as possible.

While the old Tek 2465 displays a sensible waveform, the new Rigol is clearly struggling; it looks like the logic signals are invalid.

I'm not going to explain the details of the code, other than to note that the "outPort <:0x005555ff" outputs the pattern after any previous output has completed. FFI see the introduction to xC .

Code: [Select]

clock clk0 = XS1_CLKBLK_2;
buffered out port:32 outPort = XS1_PORT_1C;
void processes() {
    configure_clock_rate(clk0, 250, 1);
    configure_out_port(outPort, clk0, 1);
    start_clock(clk0);
    while (1) {
        outPort <:0x005555ff;
    }
}

Why is the Rigol scope stopped when the Analog scope can't be stopped ? Try running the Rigol scope with repetitive triggering.

If you think about it, that makes no difference.

Also this Rigol scope is fairly old with shallow record depth and no Peak detect. Try a later scope such as the 1054Z etc.

As I said, I know how to get the expected trace: change from "normal" to "peak detect"; IMNSHO peak detect should be the normal setting!

You should compare apples with apples !! Also for digital signals you should preferably use linear interpolation rather than sinX/X interpolation.

If you read the first post, you will see I am doing exactly what many posts on this forum recommend. That is the point.

BTW, sin/x was off - and is irrelevant anyway.

The bandwidth of this Rigol scope is only 50 MHz and your analog scope is 350-400MHz ? That in itself a huge discrepancy !!

Good luck to you if you find your analog scope more useful for measuring protocols and counting bits. You'd be the exception to the rule.

[lem_ix]

Your definition of beginner seems a bit different to what we usually experience on the forum imo.

This hypothetical beginner has grown past the arduino/raspi. Doesn't use a breadboard. Understands that using a probe aligator clip doesn't give sensible measurements in many cases. Knows about probe impedance, lo-z probes and can make them or has them available. But is somehow confused about rise time and signal bandwidth and thinks those Mhz numbers printed on the scope are just a doodle. Somewhat unrealistic if you ask me and doubtful if such a measurement actually matters much for a beginner. Members that actually show some knowledge get recommendations more tailored to their needs. Also if someone is choosing between analog and digital, is it worth dropping all the benefits of a digital scope for this one case where the analog one is better?(not saying you shouldn't get both if you need bw cheaply)

Digital scopes are the norm today, the only reason I would ever recommend an analog one is if someone needed cheap bandwidth for analog like work(Repetitive) and has the skills to repair one.

Also analog scopes are not necessarily cheaper....
Prices today from the local "Ebay" clone :

Tektronix 466 - 323 Euro
Tektronix 5113 - 370 Euro
Hameg HM-203-6 - 290 Euro
Goldstar OS-9020A - 320 Euro

Need I say more? Didn't know analog scopes were made out of gold. Sure this is not the case everywhere but do take that into consideration.
Point being, while I sorta understand where you're going with this I find it terribly far fetched.

[tautech]

For what its worth, when I was looking to buy an entry level scope analog just wasn't an option.

For a complete beginner buying used equipment of unknown condition is a massive risk.  Not only are you incapable of repairing problems (even simple ones) with the scope, but you don't even feel qualified to judge whether the scope is working properly in the first place.

Used scopes can become pretty pricy outside of the USA, and spending that kind of money just doesn't seem smart when the 1054z exists.

Now when you start looking to buy a second scope many of the used analogs start to become very interesting.

We pretty much agree.

A beginner should only have a working scope, of whatever type. Taking on a "restoration project" is only for those that enjoy doing that and are prepared to take some risks!

If money is a serious consideration, which is likely on this forum, then it may be worth considering a very cheap very basic analogue scope. I don't know where you are based, but in the UK if you are patient you can find working examples at about £1/MHz, and frequently they are simply given away. (My local hackspace will shortly be throwing half a dozen out, unless members want them!)

This is the big problem.  There are lots of good used and inexpensive analog oscilloscopes out there but the people who could make the best use of them do not have the experience to recognize or maintain them.

For this reason, I usually end up recommending the Rigol DS1000Z or similar despite my misgivings unless they have someone who can help them find a less expensive alternative.

And I agree, while there's little point in having two very similar scopes (or tools), it can be worth having significantly different scopes (or tools) - so that you can use the unique advantages of each as appropriate. That's why I also have a new 10MHz (not 100MHz) digitizing storage scope.

Despite being a big believer in this, I still have duplicate oscilloscopes but only because I end up fixing every one of them.

Bingo. 

Your definition of beginner seems a bit different to what we usually experience on the forum imo.

This hypothetical beginner has grown past the arduino/raspi. Doesn't use a breadboard. Understands that using a probe aligator clip doesn't give sensible measurements in many cases. Knows about probe impedance, lo-z probes and can make them or has them available. But is somehow confused about rise time and signal bandwidth and thinks those Mhz numbers printed on the scope are just a doodle. Somewhat unrealistic if you ask me and doubtful if such a measurement actually matters much for a beginner. Members that actually show some knowledge get recommendations more tailored to their needs. Also if someone is choosing between analog and digital, is it worth dropping all the benefits of a digital scope for this one case where the analog one is better?(not saying you shouldn't get both if you need bw cheaply)

Digital scopes are the norm today, the only reason I would ever recommend an analog one is if someone needed cheap bandwidth for analog like work(Repetitive) and has the skills to repair one.

Also analog scopes are not necessarily cheaper....
Prices today from the local "Ebay" clone :

Tektronix 466 - 323 Euro
Tektronix 5113 - 370 Euro
Hameg HM-203-6 - 290 Euro
Goldstar OS-9020A - 320 Euro

Need I say more? Didn't know analog scopes were made out of gold. Sure this is not the case everywhere but do take that into consideration.
Point being, while I sorta understand where you're going with this I find it terribly far fetched.

Bingo +2

This is an art, deducing the experience of those seeking help and offering the right advice/solution.
NO one solution fits all and while the many greybeards here would happily grab a CRO, for novices with little electronic and especially HV experience to advise them to spend money on a CRO is irresponsible.

[tggzzz]

Sorry, read the title then saw it was about Rigol scopes vs some analog relic.  I gave away my old Hitachi analog scope and my newer Lecroy but kept the first one I ever owned, the 7200.   VME chassis, 68K based relic from the USAF's past.   Not exactly what I would consider the high end of the curve.   I would even go so far as to call it a very low end DSO by todays standards, or even my other DSOs.   

I'll have to check the little micro use used.   Rather than go that route, I just programmed my old Sony Arb with your pattern and roughly the same levels.   From the 2nd picture, you will see this is a single shot.   Third picture, turned on the auto measure and RIS with the 4GHz sampler.   

Like I said, it's a relic but I still use it any time I think I may damage something.  I can't think of a time I would have needed an analog scope or an analog handheld meter for that matter.   I do still have my vacuum tube grid dip meter.

I hadn't spotted that you had changed the contents of your posting, adding significant content.

Bear in mind that my whole posting is not related to expensive professional scopes, but is related to the class of cheap scopes frequently and forcefully recommended in this forum - and to what extent they are suitable for bit-bashed digital signals.

What's the 7200's basic spec, particularly the front-end analogue bandwidth? Given that LeCroy is a long-standing decent professional brand, I would hope and expect  that it would perform "without surprises". I don't see any surprises in the second screenshot.

I don't understand what the Arb Generator screenshot is showing, and can't see the waveform it is generating. Certainly 400kHz is much slower than the waveform I generated (bit period 4ns). The voltage levels ought to be irrelevant.

I don't understand what the last screenshot is showing, nor how it relates to the issue I've mentioned.

If you are interested in hard realtime multicore parallel systems, the XMOS processors and xC are definitely worth understanding. Their pedigree (people, theoretical basis, practical experience) dates back to the 70s in the form of CSP, Occam, Links/Channels and the Transputer. Some of the concepts have found a place in very different systems, e.g. some TI DSPs.

The Arb screenshot is some crappy app I put together to drive my old Sony.  The waveform is shown in the bottom of the screen. 

No wonder it didn't mean anything to me, nor probably to other people.

Now we come to the fundamental problem.  I had assumed you knew how to read a scope.  You are at 20ns/div.  I also show 20ns/div.  Count the number of cycles per division on my screen shot and what do you see?  Maybe that I am actually running a little faster than you, not slower.   

Oh, I can. Notice that I didn't question the middle trace, since it that was obvious.

The bottom trace looks like a sine wave without any clear indication of what's on each axis. I did not see why you were showing that.

A terse explanation of why you are showing a picture (e.g. a title) is very helpful for your audience.

In your original post you state

The first point to note is that the 80:20 transition times of the output is 1ns (90:10 is 1.8ns).

  The last screen shot shows a rise and fall time (10/90) of 1.3ns.  Those digital readouts must have thrown you off.      Anyway, I wanted you to see that it was in the ballpark (slightly faster edge) than what you show.   

The 7200 is a modular scope.  The 7242B w/50 ohm coupling has an analog BW of 500 MHz.  Looking at the edge rates, I was using the 7262 which has a 4GHz bandwidth, 10 bits vertical and 100GS/s (RIS). 

As I mentioned, I gave away my one Lecroy that was much nicer than this one.   There is no color LCD screen so not much value to the beginner.  I bought the Hitachi brand new and rarely ever used it after I bought this old LeCroy.  The only advantage the Hitachi had was weight and size.

**** Small update ****
Just in case there was some question about how the old relic would handle the 10ns pulses at 10KHz in single shot.  I figure 12ns ish was close enough for you. 

In case you missed it, I also attached a screen capture of what I did to simulate your pattern test.

Thank you for the essential information allowing us to interpret what you are showing.

This thread is about the standard advice given to beginners on this forum, to wit that a new low-end 50/100MHz digitising scope is all you need for bit-bashed digital signal, and that cheaper older analogue scopes are useless.

You show a high-end professional 500MHz scope, so while all your statements are correct, they are not comparable.

OTOH I would certainly agree that your LeCroy is more than adequate for that job, and, like you, I would advise a beginner to ignore the lack of a colour LCD display!

[tggzzz]

The bandwidth of this Rigol scope is only 50 MHz and your analog scope is 350-400MHz ? That in itself a huge discrepancy !!

Of course it is! The point is that a £85 old scope has a much more faithful measurement (in significant respects) than a new £275 scope. While that's never the only consideration, it is significant.

Good luck to you if you find your analog scope more useful for measuring protocols and counting bits. You'd be the exception to the rule.

I don't know what you mean by "measuring protocols and counting bits". That scope (and many others like the Tek 2xxx ranges) measures time/frequency/voltage.

When I want to interpret the analogue voltages as a character or number, no, I certainly don't use a scope for anything more than a trivial quick look. If I want to look at digital information then I use digital domain tools: logic analyser or printf statements.

In this case I would be very surprised if a protocol decode correctly interpreted the signal in the second post. And, quite frankly, it shouldn't be able to interpret it correctly since it appears to be an invalid digital signal.

[tggzzz]

For what its worth, when I was looking to buy an entry level scope analog just wasn't an option.

For a complete beginner buying used equipment of unknown condition is a massive risk.  Not only are you incapable of repairing problems (even simple ones) with the scope, but you don't even feel qualified to judge whether the scope is working properly in the first place.

Used scopes can become pretty pricy outside of the USA, and spending that kind of money just doesn't seem smart when the 1054z exists.

Now when you start looking to buy a second scope many of the used analogs start to become very interesting.

We pretty much agree.

A beginner should only have a working scope, of whatever type. Taking on a "restoration project" is only for those that enjoy doing that and are prepared to take some risks!

If money is a serious consideration, which is likely on this forum, then it may be worth considering a very cheap very basic analogue scope. I don't know where you are based, but in the UK if you are patient you can find working examples at about £1/MHz, and frequently they are simply given away. (My local hackspace will shortly be throwing half a dozen out, unless members want them!)

This is the big problem.  There are lots of good used and inexpensive analog oscilloscopes out there but the people who could make the best use of them do not have the experience to recognize or maintain them.

For this reason, I usually end up recommending the Rigol DS1000Z or similar despite my misgivings unless they have someone who can help them find a less expensive alternative.

All true.

The Rigols are good value for money, and sufficient for many purposes. But they are not as good as some people claim for some relevant use cases (bit-bashed signals).

And I agree, while there's little point in having two very similar scopes (or tools), it can be worth having significantly different scopes (or tools) - so that you can use the unique advantages of each as appropriate. That's why I also have a new 10MHz (not 100MHz) digitizing storage scope.

Despite being a big believer in this, I still have duplicate oscilloscopes but only because I end up fixing every one of them.

I'm trying to break that habit; it is difficult

[nctnico]

The scope needs to be matched to likely and expected work it is going to be used on and I can't help but think that sometimes features on scopes etc are for a lot of people, like features on cars, bragging points that can used in a game of top trumps.

That is an absolutely key point that many people on this forum repeatedly mention - and many people dogmatically don't mention. The aphorism in my .sig has direct analogies with electronics, as your posting indicates you already know

I start to see parallels with you repeating your objections against C++. The whole world seems to think differently.

[tggzzz]

This hypothetical beginner has grown past the arduino/raspi. Doesn't use a breadboard. Understands that using a probe aligator clip doesn't give sensible measurements in many cases. Knows about probe impedance, lo-z probes and can make them or has them available. But is somehow confused about rise time and signal bandwidth and thinks those Mhz numbers printed on the scope are just a doodle. Somewhat unrealistic if you ask me and doubtful if such a measurement actually matters much for a beginner. Members that actually show some knowledge get recommendations more tailored to their needs. Also if someone is choosing between analog and digital, is it worth dropping all the benefits of a digital scope for this one case where the analog one is better?(not saying you shouldn't get both if you need bw cheaply)

There is, of course, a continuum and many people here are extremely knowledgeable. Anyone that knows the beneficial characteristics of loZ probes isn't a beginner! Apart from that, I believe I covered (and agreed with) your last point in paragraph 6 of my first post ("Before replying...").

Digital scopes are the norm today, the only reason I would ever recommend an analog one is if someone needed cheap bandwidth for analog like work(Repetitive) and has the skills to repair one.

I don't disagree. Single shot is the killer advantage of digitising scopes. Analogue storage scopes always were a pain in the backside, and only used because there was no alternative!

My posting indicates that low-end digitising scopes are misleading when looking at the outputs from low-end DevKits in simple use cases.

Also analog scopes are not necessarily cheaper....
Prices today from the local "Ebay" clone :

Tektronix 466 - 323 Euro
Tektronix 5113 - 370 Euro
Hameg HM-203-6 - 290 Euro
Goldstar OS-9020A - 320 Euro

Need I say more? Didn't know analog scopes were made out of gold. Sure this is not the case everywhere but do take that into consideration.

Oh, I can find much higher asking prices on fleabay! I've no idea why anyone would think of paying £650 for a 2465! If that was a realistic price I'd sell my 2465 like a shot!

Point being, while I sorta understand where you're going with this I find it terribly far fetched.

As I indicated in the initial post, I deliberately "over egged" the position to make the point, and chose extreme - but realistic - examples. To that extent it isn't "terribly far-fetched", although it certainly is on the boundary.

[nctnico]

My posting indicates that low-end digitising scopes are misleading when looking at the outputs from low-end DevKits in simple use cases.

And that is based on just one sample using an old DSO which has been deliberatly setup wrong too! Your posting would have been much more informative to beginners when it showed how to do the same measurement.

[tggzzz]

The scope needs to be matched to likely and expected work it is going to be used on and I can't help but think that sometimes features on scopes etc are for a lot of people, like features on cars, bragging points that can used in a game of top trumps.

That is an absolutely key point that many people on this forum repeatedly mention - and many people dogmatically don't mention. The aphorism in my .sig has direct analogies with electronics, as your posting indicates you already know

I start to see parallels with you repeating your objections against C++. The whole world seems to think differently.

That's an entirely different topic. If you believe the "whole world seems to think differently", then you have a blinkered weltanschauung. (30 years ago someone made similar statements to me about COBOL!)

[tggzzz]

My posting indicates that low-end digitising scopes are misleading when looking at the outputs from low-end DevKits in simple use cases.

And that is based on just one sample using an old DSO which has been deliberatly setup wrong too! Your posting would have been much more informative to beginners when it showed how to do the same measurement.

The 10kHz waveform deliberately used the "normal" acquisition setting. I explicitly drew attention to the fact there are more appropriate settings. Personally I think that beginners would be helped if the "peak detect" (which isn't actually a peak detect, but that's a different point) was the first and normal setting.

If there is a way the 0x005555ff waveform could be improved, let me know. If there is a significant improvement, I will show it.

[joeqsmith]

The bottom trace looks like a sine wave without any clear indication of what's on each axis. I did not see why you were showing that.

A terse explanation of why you are showing a picture (e.g. a title) is very helpful for your audience.

....

Thank you for the essential information allowing us to interpret what you are showing.

No problem.  I had assumed you would know I was looking at the bit timing.   My bad.   

This thread is about the standard advice given to beginners on this forum, to wit that a new low-end 50/100MHz digitising scope is all you need for bit-bashed digital signal, and that cheaper older analogue scopes are useless.

You show a high-end professional 500MHz scope, so while all your statements are correct, they are not comparable.

OTOH I would certainly agree that your LeCroy is more than adequate for that job, and, like you, I would advise a beginner to ignore the lack of a colour LCD display!

There was no mention of the 50/100MHz Rigol in the title or about advice to beginners.  Just how old analog scopes beat new digital ones. Seemed interesting enough and why I added my placeholder.  You are correct, the 7200 was a high-end professional scope of it's time. I guess the spear was high tech, along with the bow and arrow and musket.  I would imagine most modern 500MHz DSOs would outperform it except maybe for the math functions.   

[tggzzz]

Your quoting seems a little cocked up; I believe I've corrected it. Never ever made that mistake, oh no 

The bottom trace looks like a sine wave without any clear indication of what's on each axis. I did not see why you were showing that.

A terse explanation of why you are showing a picture (e.g. a title) is very helpful for your audience.

....

Thank you for the essential information allowing us to interpret what you are showing.

No problem.  I had assumed you would know I was looking at the bit timing.   My bad.   

It is easy to overestimate your audience!

This thread is about the standard advice given to beginners on this forum, to wit that a new low-end 50/100MHz digitising scope is all you need for bit-bashed digital signal, and that cheaper older analogue scopes are useless.

You show a high-end professional 500MHz scope, so while all your statements are correct, they are not comparable.

OTOH I would certainly agree that your LeCroy is more than adequate for that job, and, like you, I would advise a beginner to ignore the lack of a colour LCD display!

There was no mention of the 50/100MHz Rigol in the title or about advice to beginners.  Just how old analog scopes beat new digital ones. Seemed interesting enough and why I added my placeholder.  You are correct, the 7200 was a high-end professional scope of it's time. I guess the spear was high tech, along with the bow and arrow and musket.  I would imagine most modern 500MHz DSOs would outperform it except maybe for the math functions.

I deliberately omitted mentioning a specific scope since I wanted people to concentrate on the generic waveforms and performance, not on one specific scope.

As you say, tech progresses - but in both instrument and circuit speeds.

• in yesteryears, bog-standard scopes (10MHz) weren't good enough for looking at bog-standard logic (74/74LS/etc) and embedded processor (8080/Z80/6809) outputs; a 465 class machine was necessary
• similarly, now a bog-standard (50/100MHz) digitising scope isn't good enough for looking at bog-standard logic (74LVC/etc) and embedded processor (e.g XMOS xCORE) outputs; a 350MHz(ish) machine is necessary

But, at the moment, there is an overlap where reasonably priced analogue scopes offer a significant advantage in the important use-case of bit-bashed processor outputs.

My objection is to people that refuse to acknowledge that, often wrapped up in a newer-is-always-better mentality.

[Fungus]

My objection is to people that refuse to acknowledge that, often wrapped up in a newer-is-always-better mentality.

Yep. Everybody should be buying old analog 'scopes based on a single pathological case that's easy to avoid.

(not that a newbie would ever type that trollcode anyway)

[tggzzz]

My objection is to people that refuse to acknowledge that, often wrapped up in a newer-is-always-better mentality.

Yep. Everybody should be buying old analog 'scopes based on a single pathological case that's easy to avoid.

Excellent - please enlighten us as to how you think the 0x005555ff example can be avoided. I'll try it and if there is a significant improvement, I'll show it.

(not that a newbie would ever type that trollcode anyway)

You've already implicitly acknowledged that is an irrelevant detail; repeating the statement doesn't show you in a good light.
https://www.eevblog.com/forum/testgear/old-analogue-scopes-beat-new-digital-scopes-for-bit-bashed-digital-outputs/msg1220024/#msg1220024

[David Hess]

The bandwidth of this Rigol scope is only 50 MHz and your analog scope is 350-400MHz ? That in itself a huge discrepancy !!

But that 50 MHz DSO should still be faithfully reproducing the signal within the constraints of its 50 MHz bandwidth and it is not doing that; there are signal artifacts, especially on the trailing edge but also at the beginning of the pulse train, which simply do not exist.  The 350 MHz oscilloscope result simply shows what should not be there; the DS1052E is displaying something which does not exist.

I actually find it difficult to believe that the 50 MHz DS1052E (or any oscilloscope) produced that result unless it was broken; to me it looks more like a probe problem.  tggzzz, your original post says that you used a 1.5GHz Z0 (low-z?) probe but could you describe the probe in more detail? How was it connected to the DS1052E? Was it through the needed feedthrough termination? It should not matter but was the same feedthrough termination used on the 2465 or was its internal termination used?  Could the DS1052E have been damaged before the test?

[Fungus]

You've already implicitly acknowledged that is an irrelevant detail;

Nope.

Setting the clock to 250MHz and outputting one '1'obviously the same as setting it to 1000MHz and outputting four '1's. 

If you were interested in anything other than trolling you'd have said something like "I had to output X 1's to get it the pulse to show on the 50MHz DSO when 4 was enough on the analog scope with six times the bandwidth".

I suspect X might be 5, because 4 is almost showing on the DSO. Why don't you change the code to output five 1's for us...?

[joeqsmith]

Your quoting seems a little cocked up; I believe I've corrected it. Never ever made that mistake, oh no 

  Seldom review what I post.  It would take me too long to correct all my mistakes.

But, at the moment, there is an overlap where reasonably priced analogue scopes offer a significant advantage in the important use-case of bit-bashed processor outputs.

My objection is to people that refuse to acknowledge that, often wrapped up in a newer-is-always-better mentality.

Right, I can understand your point.  The only thing I am suggesting is that there may be reasonably priced vintage DSOs that would also offer some pretty big advantages over an analog or low end DSO. 

[tggzzz]

But, at the moment, there is an overlap where reasonably priced analogue scopes offer a significant advantage in the important use-case of bit-bashed processor outputs.

My objection is to people that refuse to acknowledge that, often wrapped up in a newer-is-always-better mentality.

Right, I can understand your point.  The only thing I am suggesting is that there may be reasonably priced vintage DSOs that would also offer some pretty big advantages over an analog or low end DSO.

We are in violent agreement

My only caveat would be that recent DSOs are usefully more mature and usable than some of the earlier DSOs. Examples would include 1GHz 25MS/s scopes (top of HP's range at the time!), and (less seriously) scopes where vertical sensitivity changes are via the "calibrate" softkey. That doesn't invalidate your point, it merely alerts people that more care is taken in selecting such a scope.

[ebclr]

 

[free_electron]

why are we using an oscilloscope to check timing of digital systems in the first place ? that's what logic analyzers with state/timing analysis were designed for...

[tggzzz]

why are we using an oscilloscope to check timing of digital systems in the first place ? that's what logic analyzers with state/timing analysis were designed for...

I wish more people thought like that! Scopes should be used to ensure signal integrity, and thereafter debugging should flip to the digital domain.

In this case the reason is twofold: the traditional statements on this forum w.r.t. analogue vs digitising scopes and their uses, plus the 250Mb/s 4ns serial bit rates bashed out of the processor.

[Fungus]

the 250Mb/s 4ns serial bit rates bashed out of the processor.

...which you tried to look at on an old 50MHz DSO before pronouncing your verdict.