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.
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.
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.
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.
QuoteBack 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).
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).
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.
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.
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.
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.
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.
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.
on paper the 2072A offers over double the spec:
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.
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.
If you had been around 30-40 years ago, you would have loved bit slice processors such as the AMD2900 or Intel 3000 families.
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.
QuoteThat'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'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.
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.