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How good of a DMM or Oscope could you make with modern CPU or GPU ?
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SiliconWizard:

--- Quote from: 2N3055 on June 26, 2022, 07:04:58 pm ---
--- Quote from: nctnico on June 26, 2022, 10:58:12 am ---
--- Quote from: Someone on June 26, 2022, 05:51:44 am ---The basic challenge for commodity computer hardware is first bus throughput (how many consumer interfaces carry 4 channels of 10GS/s data? 320Gbit per second) and then what to do with that torrent of data... in short commodity CPUs or GPUs make for really crap scopes compared to task specific ASIC or FPGA designs.

--- End quote ---
And yet that is exactly how Lecroy's higher end scopes are built: a relatively dumb sampler and then do all the post processing using CPU + GPU. With ever increasing bandwidths of SOC based systems it is not out of reach to build a low cost scope without doing a lot of processing inside an FPGA. FPGAs take a lot of time to develop and are limited where it comes to resources.

--- End quote ---
LeCroy scopes have significant FPGA resources inside.. It deals with triggering engine and decimation and corrections etc etc..
It is measurements and display and decodes that are done on CPU... But they do more processing on CPU than anybody else..

--- End quote ---

Yeah.

Even so, most scopes these days do a lot in "hardware". Some with dedicated ASICs, some with just FPGAs and off-the-shelf parts.

Tektronix used to use x86 motherboards and Windows for the GUI at some point, like in the TDS510x series.
These days, ARM SOCs are common and powerful enough in combination with the above hardware to handle even a sophisticated scope.
A very common approach at least in the low and even mid-range scopes is to use those ARM core(s)+FPGA hybrids such as the Xilinx Zynq parts.

Scopes requiring more graphics power can use ARM SOCs with an integrated GPU.

Approaches vary slightly at least for the higher-end scopes, depending on the vendor. Both for performance, and for marketing reasons.
David Hess:

--- Quote from: robert.rozee on June 26, 2022, 05:14:31 am ---re-framing the question: given a modern-ish CPU coupled closely to an ADC and a low-complexity front-end, what sort of actual performance could be attained; what would be the realistic top sample rate, and realistic bandwidth?

lets say one started with a Raspberry Pi 3 for instance, and add on a PCB containing 2-channels of input and a pair of ADCs with a maximum parts cost of, say $20. what could be achieved?
--- End quote ---

The problem is not processor power.  Real time DSOs have been implemented with 16-bit 8088 class processors.  Today even a mediocre ARM has two order of magnitude better performance.

The problem is capturing the high sample rate acquisition record into memory where the processor can get to it.  Most processors either lack a suitable interface, or the external interface logic is so complex that there is no reason not to move decimation and other functions to the same dedicated external logic, which is what early DSOs did and what most modern DSOs do.

So find a processor that can interface directly to two or more 8-bit ADCs at 100s of megasamples per second each.  Does anybody make a PCIe ADC?
thm_w:
Any sort of decent PCIE ADC I can find is basically a scope on a card with FPGA already, or has very low sample rate, etc.

https://acqiris.com/8-bit-adc-card/
https://www.ni.com/en-ca/shop/hardware/products/pxi-analog-input-module.html (probably wont fit in a normal PC but same idea)
https://www.ni.com/en-ca/shop/pxi/pxi-modules.html
https://www.acquitek.com/product/px1500-2-2/
https://spectrum-instrumentation.com/products/families/22xx_m4i_pci.php

The last one is sort of relevant to OP, as it says "Direct data transfer to CUDA GPU using SCAPP option"

Then of course there is the issue that its going to be a niche card, which means its expensive, already more so then an equivalent full scope.
The idea is good, but, I can't see it being executed in any normal budget.

The closest execution might be those low cost VGA USB3 devices, I think you could use those as high speed DACs.
MathWizard:
I forgot about this thread, lots interesting answers. So a desktop CPU/GPU just isn't built for making the best scope or DMM. And if a dream team at intel decides to make a scope/DMM, they would probably just cook up a new chips then.

And yeah I'm impressed by the speed of the latest PC tech, but I forget, there are muilti-GHz oscilloscopes, that cost more than most houses in Canada.

I'm just reading the thread "Oscilliscope memory, type and why so small?", and it reminds me tho of some user interface limitations, that DMM and scopes still have vs the entire PC package, or laptop even. All my Siglent stuff can be plugged into the PC, but it's a long ways from if Siglent said, lets make a scope/DMM/PSU/AWG/etc , all in one box like a PC, with a big screen, and KB/mouse, and full GUI, for those that want more than command line stuff.


I'm sure the tech people from Intel/AMD meet up with the tech guys from Fluke, Tektronix etc, and think about this too.
ebastler:

--- Quote from: MathWizard on July 22, 2022, 04:59:13 am ---And if a dream team at intel decides to make a scope/DMM, they would probably just cook up a new chips then.

--- End quote ---

Or they might decide to buy an FPGA company like Altera. Oh, wait...


(No, I don't think Intel bought them because they plan to enter the scope market. ;)  But they obviously realize that there are things that an FPGA does much better than a CPU or GPU. I wonder whether we should expect SoCs with an Intel CPU and Altera FPGA core at some point? The current "Intel" SoCs are Altera designs using ARM CPU cores, of course.)
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