Best entry level oscilloscope for computer engineering?

[Wuerstchenhund]

I'd be pretty unfazed (see what I did there) about using a 100MHz BW 250Gsa/s per ch scope on a 33MHz bus.

Remember that a lot of what you're seeing isn't 33MHz, maximum data change rate on worst case is half that.

For things like RAS and CAS, you're looking at relative timing and phase differences, and for set up and hold times etc, 250Gsa/s may just about cut it, if not go up to 500Gsa/s per ch by only using 2ch and work from there.

I guess you mean MSa/s, not GSa/s.

Back in the days of the 33MHz bus CPU, in the early 90s, there were pretty much no DSOs that would accomplish single shot 1Gsa/s, but I stand to be corrected of course.

That's wrong, there were actually quite a few scopes that could do single shot 1GSa/s the early '90s, for example the HP 54510A (my work horse back then).

[alank2]

One thing to also consider when looking at scopes is how the sample rate goes down with the number of enabled channels.

DS1054Z - 1ch=1GSa/s, 2ch=500MSa/s, 4ch=250MSa/s.
DS2072 - 1ch=2GSa/s, 2ch/1GSa/s
DS4014 - 1ch=4GSa/s, 2ch=4GSa/s (CH1 + CH3), 4ch=2GSa/s

[Howardlong]

Some shots I took a few hours ago on an MSO1074Z decoding SPI at 50MHz, one with LA  at 1Gsa/s (it still works at 250Msa/s) and the other on analogue channels a 250Msa/s... (which, by the way I can't currently seem to get to decode on an Agilent/Keysight MSO7104B 1GHz/4GSa/s scope which appears to give up beyond 35MHz for SPI on my unit, errors of operator excepted and accepted of course).

Edit: probing on analogue channels is with stock probe end clips and crocodile ground leads attached close by: I don't necessarily recommend that at these speeds, but that's what worked unexpectedly consistently well on this occasion.





Note that triggering on the Rigol in SPI seems not so good in SPI. Couldn't get that to work, I think I covered this in another thread a month or so ago.

Edit II: changed GSa/s to MSa/s, due to operator having a Saturday night brain fart.

[tggzzz]

I'd be pretty unfazed (see what I did there) about using a 100MHz BW 250Gsa/s per ch scope on a 33MHz bus.

Remember that a lot of what you're seeing isn't 33MHz, maximum data change rate on worst case is half that.

For things like RAS and CAS, you're looking at relative timing and phase differences, and for set up and hold times etc, 250Gsa/s may just about cut it, if not go up to 500Gsa/s per ch by only using 2ch and work from there.

I guess you mean MSa/s, not GSa/s.

Not necessarily, iff you are looking at timing differences in repetitive signals using equivalent time sampling rather than real-time one-shot sampling.

[Howardlong]

I'd be pretty unfazed (see what I did there) about using a 100MHz BW 250Gsa/s per ch scope on a 33MHz bus.

Remember that a lot of what you're seeing isn't 33MHz, maximum data change rate on worst case is half that.

For things like RAS and CAS, you're looking at relative timing and phase differences, and for set up and hold times etc, 250Gsa/s may just about cut it, if not go up to 500Gsa/s per ch by only using 2ch and work from there.

I guess you mean MSa/s, not GSa/s.

Indeed, my error.

Back in the days of the 33MHz bus CPU, in the early 90s, there were pretty much no DSOs that would accomplish single shot 1Gsa/s, but I stand to be corrected of course.

That's wrong, there were actually quite a few scopes that could do single shot 1GSa/s the early '90s, for example the HP 54510A (my work horse back then).

I didn't realise that was single shot, I assumed it must've been equivalent time. That must've been quite something back then. I'd jumped ship and was software guy in the late 80s & 90s so I'll hold my hands up and accept your superior knowledge. Did anyone else do that calibre of DSO in single shot at that time?

[nctnico]

Tektronix had the TDS600 series realtime scopes in that era going up to several Gs/s IIRC.

[nbritton]

Signals don''t vanish above the rated bandwidth, they just attenuate (get smaller). This affects harmonics and changes the shapes of things. If you know signal theory and practice a bit then you can compensate in your head (up to a point).

I don't know signal theory. I don't know pcb layout. The extent of my experience is I dabbled in analog electronics in high school and aced college level circuit analysis. I haven't done electronics in over a decade. I have a renewed interest in this, as a hobby, because I'm now living in a small apartment in a big city that is expensive to live in. I need a hobby that doesn't take up a lot of space, I also need a hobby that is connected in some way to my profession as a Linux system engineer. I find programming semi-boring, I've always been drawn to hardware. Perhaps I'm being too ambitious, what is realistic for someone who is a novice amateur? Money is not the most highest concern for me, I'm more interested in buying the right tools for the job. The only scope I've owned is a Tektronix 2213.

[nbritton]

You can probably design and build the whole thing without measuring any hardware at all. After its built (and if it's not working) you might need to measure some clock lines, to verify they are actually clocking, but I very much doubt you need to measure anything on a 32bit wide memory bus. Again you might probe a line or two to ensure it looks ok.  Because your hardware will be fairly expensive to build, you would be wise to invest time in setting up software simulations to ensure theoretical signal integrity of your board design. A basic 100mhz scope will be fast enough to indicate if a 33mhz clock line is working or not. I'd say it would be a fairly ambitious project if you don't have a heap of pcb layout experience.

Then what do I need a scope for? Wouldn't I be just as well off with frequency counter? Seriously, if I don't need to care about what the waveform looks like why do I need a scope?

Edit: Also what am I learning here? My goal in building a computer from scratch isn't to learn pcb layout, it is to gain a deeper understanding of how a computer operates so that I can apply that knowledge to my job as a Linux system engineer.

[tggzzz]

You can probably design and build the whole thing without measuring any hardware at all. After its built (and if it's not working) you might need to measure some clock lines, to verify they are actually clocking, but I very much doubt you need to measure anything on a 32bit wide memory bus. Again you might probe a line or two to ensure it looks ok.  Because your hardware will be fairly expensive to build, you would be wise to invest time in setting up software simulations to ensure theoretical signal integrity of your board design. A basic 100mhz scope will be fast enough to indicate if a 33mhz clock line is working or not. I'd say it would be a fairly ambitious project if you don't have a heap of pcb layout experience.

Then what do I need a scope for? Wouldn't I be just as well off with frequency counter? Seriously, if I don't need to care about what the waveform looks like why do I need a scope?

Edit: Also what am I learning here? My goal in building a computer from scratch isn't to learn pcb layout, it is to gain a deeper understanding of how a computer operates so that I can apply that knowledge to my job as a Linux system engineer.

The more you say about your goals, the more we can avoid spending our time making suggestions that you find irrelevant.

Have a look at the arduino ecosystem, and pick a project to do with an arduino plus shields plus your custom hardware.

[nctnico]

I'm getting that idea as well. An Arduino or Raspberry Pi will be much more rewarding than tinkering with obsolete hardware. The same baic principles still apply though.

[tggzzz]

I'm getting that idea as well. An Arduino or Raspberry Pi will be much more rewarding than tinkering with obsolete hardware. The same baic principles still apply though.

The arduino has the advantage (for the OP) of being much simpler and closer to bare-silicon. There's no operating system in the way. The bootloader loads the program and gets out of the way - much like MSDOS

The RPi is much more "powerful" because it is linux based (which may be a disadvantage for the OP) - but also much more complex.

Either will have the advantage (compared with building an i486) that the OP can quickly use them to do something, rather than just exist.

[D3f1ant]

Then what do I need a scope for? Wouldn't I be just as well off with frequency counter? Seriously, if I don't need to care about what the waveform looks like why do I need a scope?

Edit: Also what am I learning here? My goal in building a computer from scratch isn't to learn pcb layout, it is to gain a deeper understanding of how a computer operates so that I can apply that knowledge to my job as a Linux system engineer.

I would suggest perhaps the most challenging part of building a computer from scratch is going to be the board layout. Don't underestimate the importance the board design plays on high speed signals, its not just about ensuring pins are connected to each other. You will then need the scope to see that the signals are present, correct and signal integrity is there.

[nbritton]

I've played with the arduino and raspberry pi and I didn't find them very challenging, with these devices it largely came down to programming and that's not really what I'm interested in learning. What I want to learn are things like how digital electronics work, how a CPU works, how memory works, how to interface with memory and perform operations on the bits stored in it, how buses work and how data is transferred around the system, how you assemble bits into higher ordered data structures, how to program in machine code and assembly language, how bootloaders work, and last but not least why operating systems are designed the way they are. Basically I want to learn in great detail how you get from electrons to a functional computer.

Edit: I'm more interested in the architecture then anything else, that's why I initially said I would like to build a 1970s era computer. Computers from this era still had discrete components. Thinking about it more, I think the first step would be to build a simplistic microcontroller from discrete components. This would help me learn things like gates, digital logic, adders, ALUs, microcode, etc. Does anyone know of a training kit that has all of this? I think a lot of this could be done in simulation or on a FPGA today, however, I want to be able to touch it. I learn best through hands on labs.

[D3f1ant]

So don't use the boatloader or built in OS on an Arduino. Erase it and start from scratch. If you want to write your own OS and or kernel in assembler that last thing your going to want is to do it on unproven hardware.

Arduino is a relativly simple microcontroller and if you program it in assembler it will be about as close as you can get to the silicon, but is still actually achievable. You'll no doubt get frustrated and turn to C fairly quickly, but even in C you will still be required to manipulate registers in bits and bytes, and will certainly teach you how the guts of it work when it's not handed to you on a plate by an off the self OS.
I still write some things in assembler now and then, if nothing else it's good to understand what C compiler is building.

If that's all still to easy, you could probably do the same with a 486 board I guess, erase the bios and let the fun begin.

You will still want a scope so you can verify that your bit/byte manipulation is having the desired effect on the IO line of the chip, but for the purposes of learning this stuff, any scope will do the job.

[nbritton]

So don't use the boatloader or built in OS. Erase it and start from scratch. If you want to write your own OS and or kernel in assembler that last thing your going to want is to do it on unproven hardware.
You could do the same with a 486 board, buy an old board, erase the bios and let the fun begin.

Removing the BIOS and firmware is a great idea. However, I don't know how to program an eeprom, or write machine code, or know what kind of microcode to write. We need to back up several steps.

[nbritton]

You will still want a scope so you can verify that your bit/byte manipulation is having the desired effect on the IO line of the chip, but for the purposes of learning this stuff, any scope will do the job.

Yes I'm coming back around, full circle, to the conclusion that any scope will work for what I want to do. However, I'm still on the fence if I should get an MSO, or a DSO + LA, or an MSO + discrete LA, or just a combo USB DSO/LA. When I woke up this morning I was heavy leaning towards an MSO2072A. Also I'm still on the fence whether the 2072A is a better value than the 1054Z, on paper the 2072A offers over double the spec:

300 MHz vs 100 MHz
2G Sa/s vs 1G Sa/s
56 Mpts vs 24 Mpts
500uV vs 1mV

Furthermore it has true segmented memory, statistical analysis, et. al., whereas these type of features appear to be cobbled together as an afterthought on the 1054Z. I really hate working with dodgy and poorly thought out systems because at the end of the day they just end up frustrating me; my peace of mind is worth a lot to me.

[ez24]

on paper the 2072A offers over double the spec:

at 3x the price - does not seen equal

If 2x the price I would say the odds are even

I just don't get it when someone compares a $400 scope with a $1200 one ??

[Fungus]

I'm getting that idea as well. An Arduino or Raspberry Pi will be much more rewarding than tinkering with obsolete hardware. The same baic principles still apply though.

Yes. Building a 486DX PC seems (a) Very ambitious and (b) Totally pointless. You'll be living alone on an island.

If I was going to build a computer these days I'd go for an ARM chip. If I just wanted to tinker with hardware and learn electronics I'd use Arduino.

[D3f1ant]

Starting to get somewhere. You won't need anything at the point your starting. I suggest, get a Microchip PIC EXPLORER 16 board and a PICKIT3. Start by programming it, in assembler, to flash an LED. (no really thats harder than you think, you need to do a lot of configuration to just achieve something as seemingly simple as flash a led). Next write some code to use the Analog to digital converter to sample the pot and display the result on the LEDs. Then start displaying some Text on the LCD. You'll now be into I2C buses and IO port expanders...nice useful stuff and you might even need a scope to figure out why the I2C bus isn't working for you.

You really don't need an oscilloscope for any of this...and if you don't know anything about bit manipulation or writing assembler it will keep you busy for ages. Thats why Arduino's are so popular...its all done for you and makes it seem trivial but its really not as easy as you might be thinking/expecting.

If you just want to buy some tools/toys now (and there is nothing wrong with that  ) buy a 100Mhz 4 channel scope (whatever model that is), don't buy any extra decoding stuff, learning to decode the bit streams on a bus will do you good and sounds like part of what you want to learn., You can add decoding licences later (or hack them on if thats your thing) Some scopes let you have the LA activated by software too (they send you the adapters and probes), so you can add it later if you need it so maybe look for models with lots of software upgrade options.
IMO 100Mhz is more than enough for 99% of what your likely to encounter/need, and with 4ch you can debug most things.

[tggzzz]

I've played with the arduino and raspberry pi and I didn't find them very challenging, with these devices it largely came down to programming and that's not really what I'm interested in learning. What I want to learn are things like how digital electronics work, how a CPU works, how memory works, how to interface with memory and perform operations on the bits stored in it, how buses work and how data is transferred around the system, how you assemble bits into higher ordered data structures, how to program in machine code and assembly language, how bootloaders work, and last but not least why operating systems are designed the way they are. Basically I want to learn in great detail how you get from electrons to a functional computer.

That sounds great; I wish more people had that understanding.

You could get a good understanding of most of those by starting at the atmega328 chip level and initialising all the hardware yourself. Get an Atmel AVR Dragon, which will allow you to program and debug atmega328 devices on their own and in whatever board and system you design.

You need to pick a suitable project, one which is within your scope but will stretch your capabilities. An example of that would be  that recently I wanted to make a date/time/pill reminder for my parents that would run for months on a set of small batteries. Arduinos would have used too much power, so I started with the atmega328, programmed it in the Dragon, and then designed and constructed the board containing the MCU, battery and peripherals (switches and an LCD display).

That is a suitable level for a hardware beginner - even with something that simple you will find that you will have a lot to learn and will make many mistakes. A 100MHz scope will be very valuable - but not necessary;I didn't have one.

Be aware that, if you want to avoid subtle intermittent failures, you are going to have to learn about ground planes, decoupling, ground bounce, probing techniques and limitations, inductance, different types of capacitor, time<->frequency relationship, transmission lines, and many other topics. Those will be tractable for a beginner with a 100MHz scope if you use arduino class MCUs such as the the atmega328. If you try to build a 486 class machine from scratch, you will almost certainly have significant problems.

(If you use solderless breadboards, be prepared to spend as much time debugging the breadboard as debugging your circuit. Reason: their general frailty plus electrical characteristics inherent in their design)

Edit: I'm more interested in the architecture then anything else, that's why I initially said I would like to build a 1970s era computer. Computers from this era still had discrete components. Thinking about it more, I think the first step would be to build a simplistic microcontroller from discrete components. This would help me learn things like gates, digital logic, adders, ALUs, microcode, etc. Does anyone know of a training kit that has all of this? I think a lot of this could be done in simulation or on a FPGA today, however, I want to be able to touch it. I learn best through hands on labs.

If you had been around 30-40 years ago, you would have loved bit slice processors such as the AMD2900 or Intel 3000 families.

[tggzzz]

If you had been around 30-40 years ago, you would have loved bit slice processors such as the AMD2900 or Intel 3000 families.

You might also be interested in the "weeny bitter", see http://www.smrcc.org.uk/members/g4ugm/acc.htm August 75 and following.

[Wuerstchenhund]

I'd be pretty unfazed (see what I did there) about using a 100MHz BW 250Gsa/s per ch scope on a 33MHz bus.

Remember that a lot of what you're seeing isn't 33MHz, maximum data change rate on worst case is half that.

For things like RAS and CAS, you're looking at relative timing and phase differences, and for set up and hold times etc, 250Gsa/s may just about cut it, if not go up to 500Gsa/s per ch by only using 2ch and work from there.

I guess you mean MSa/s, not GSa/s.

Not necessarily, iff you are looking at timing differences in repetitive signals using equivalent time sampling rather than real-time one-shot sampling.

Show me a scope that does 250GSa/s or 500GSa/s ETS. Even modern scopes don't go beyond 200GSa/s for ETS, and upper high end scopes with 100+ GSa/s real-time sample rate usually don't do ETS at all any more.

[Wuerstchenhund]

That's wrong, there were actually quite a few scopes that could do single shot 1GSa/s the early '90s, for example the HP 54510A (my work horse back then).

I didn't realise that was single shot, I assumed it must've been equivalent time. That must've been quite something back then.

Well, such high sample rates weren't as common as they are today but it wasn't particularly exceptional (the 54500 Series was HP's mid-range scope series). There also was the older 54111D (1GSa/s with two channels or 2GSa/s on a single channel; came out in 1989).

Tektronix had some 1GSa/s real-time scopes at that time.

[nctnico]

I've played with the arduino and raspberry pi and I didn't find them very challenging, with these devices it largely came down to programming and that's not really what I'm interested in learning. What I want to learn are things like how digital electronics work, how a CPU works, how memory works, how to interface with memory and perform operations on the bits stored in it, how buses work and how data is transferred around the system, how you assemble bits into higher ordered data structures, how to program in machine code and assembly language, how bootloaders work, and last but not least why operating systems are designed the way they are. Basically I want to learn in great detail how you get from electrons to a functional computer.

If that is your goal you better start with a Z80 or something like that. These are easy to use (no weird cycle or clock signals like on the Motorola cpus).

[Fungus]

Thinking about it more, I think the first step would be to build a simplistic microcontroller from discrete components. This would help me learn things like gates, digital logic, adders, ALUs, microcode, etc. Does anyone know of a training kit that has all of this? I think a lot of this could be done in simulation or on a FPGA today, however, I want to be able to touch it. I learn best through hands on labs.

Get yourself a load of 74LS chips and a few dozen mini breadboards. Build an Apple II (or whatever).

I would build something simple at about 1MHz clock speed that actually has software and schematics for hardware hints.