Author Topic: Busses, serial links and required scope bandwidth  (Read 4080 times)

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Offline Wuerstchenhund

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Busses, serial links and required scope bandwidth
« on: February 19, 2016, 09:05:27 am »
Quite often the question arises what oscilloscope bandwidth is required to probe a certain bus or serial interface, so in a moment of boredom I assembled the following table from various sources.

Please keep in mind that this list shows the bandwidth required to examine the signal integrity. Decoding often works with less bandwidth, although it may be unreliable/erroneous as with insufficient bandwidth the waveform on the screen hasn't much in common with how the real signal looks like.

StandardBit RateMinimum Bandwidth req'd
Ethernet 100BT125Mbps500MHz
Ethernet250Mbps1GHz
Fibre Channel 50MB/s531.25Mbps1.5GHz
USB2 Super-Speed480Mbps2GHz
IEEE1394b Firewire 800786.43Mbps2GHz
RapidIO LP-LVDS1Gbps2.5GHz
Fibre Channel 1GFC1.0625Gbps2.5GHz
DDR2-800800MTps3.5GHz
Ethernet 1000BT1.25Gbps3.5GHz
IOF1.24416Gbps3.5GHz
RapidIO LP-LVDS1.25Gbps3.5GHz
RapidIO LP-LVDS1.5Gbps4GHz
SATA (SATA150)1.5Gbps4GHz
IEEE1394b Firewire 16001.5729Gbps4GHz
DVI1.65Gbps4GHz
HDMI 1.2a1.65Gbps4GHz
RapidIO LP-LVDS2Gbps/2.5Gbps6GHz
PCI Express 1.x2.5Gbps6GHz
DDR3-16001.6GTps8GHz
ExpressCard2.5Gbps8GHz
InfiniBand2.5Gbps8GHz
RapidIO LP-LVDS3.125Gbps8GHz
DisplayPort 1.12.7Gbps8GHz
HyperTransport 2.02.8Gbps8GHz
SAS 1.0/1.13Gbps8GHz
SGMII3.125Gbps8GHz
XAUI3.125Gbps8GHz
Firewire3.2Gbps8GHz
DDR44GTps10GHz
HDMI 1.3b3.4Gbps10GHz
SATA2 (SATA300)3Gbps10GHz
Fibre Channel 4GFC4.25Gbps13GHz
Serial RapidIO4.25Gbps/5Gbps13GHz
InfiniBand5Gbps13GHz
PCI Express Gen25Gbps13GHz
PCI Express Gen38Gbps13GHz
HyperTransport 3.05.2Gbps13GHz
USB 3.05Gbps13GHz
DisplayPort 1.25.4Gbps16GHz
GDDR56Gbps16GHz
SAS26Gbps16GHz
SATA3 (SATA600)6Gbps16GHz
Serial RapidIO6.25Gbps16GHz
HyperTransport 3.16.4Gbps16GHz
QPI6.4Gbps16GHz
10GBT10.3125Gbps20GHz
SFI/SFP+10.3125Gbps20GHz
CEI-1111Gbps25GHz
SAS312Gbps25GHz
InfiniBand25.78125Gbps50GHz
CEI-25/2825Gbps/28Gbps60GHz

I'll try to update the table from time to time.
« Last Edit: February 23, 2016, 06:29:44 am by Wuerstchenhund »
 
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Offline ADT123

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Re: Busses, serial links and required scope bandwidth
« Reply #1 on: February 19, 2016, 10:21:35 am »
Thanks for the useful table - perhaps its worth pointing out that the bandwidth requirements for decoding serial data are different from making signal integrity measurements?

Take the 250Mbps Ethernet below - you can think of that as a 125MHz square wave signal in terms of frequency.  1GHz is a sensible bandwidth for signal integrity but 500MHz would be more than enough if you are more interested in decoding the data. 

Disclaimer:  I have worked for Pico Technology for over 25 years and designed some of their early oscilloscopes. 

Happy to answer Pico related questions when I have time but I am on eevblog in a personal capacity as electronics is a hobby.
 

Offline Wuerstchenhund

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Re: Busses, serial links and required scope bandwidth
« Reply #2 on: February 19, 2016, 10:31:14 am »
Thanks for the useful table - perhaps its worth pointing out that the bandwidth requirements for decoding serial data are different from making signal integrity measurements?

Thanks for bringing this up. I've updated the original post to reflect that.
 

Offline awallin

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Re: Busses, serial links and required scope bandwidth
« Reply #3 on: February 19, 2016, 03:03:41 pm »

That's kind of depressing from a hobby-budget-scope point of view  >:D
Perhaps a list of what you *can* do with a 100MHz or 300MHz scope would be more uplifting?
 

Offline Skimask

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Re: Busses, serial links and required scope bandwidth
« Reply #4 on: February 19, 2016, 03:09:29 pm »

That's kind of depressing from a hobby-budget-scope point of view  >:D
Perhaps a list of what you *can* do with a 100MHz or 300MHz scope would be more uplifting?
<list>
1. A 56K modem...on a good day.
</list>
I didn't take it apart.
I turned it on.

The only stupid question is, well, most of them...

Save a fuse...Blow an electrician.
 

Offline Wuerstchenhund

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Re: Busses, serial links and required scope bandwidth
« Reply #5 on: February 19, 2016, 03:11:16 pm »

That's kind of depressing from a hobby-budget-scope point of view  >:D
Perhaps a list of what you *can* do with a 100MHz or 300MHz scope would be more uplifting?

Well, it would be a whole lot shorter  :-DD

But yeah, low bandwidth scopes simply don't cut it for modern high speed busses. Which I know must be depressing, as people sometimes ask for a suitable entry level scope for doing USB or Ethernet stuff. Unfortunately that's not gonna happen, even USB2 is already lower high-end territory.

And then there's the question of probing...
« Last Edit: February 19, 2016, 03:20:34 pm by Wuerstchenhund »
 

Offline tmbinc

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Re: Busses, serial links and required scope bandwidth
« Reply #6 on: February 20, 2016, 06:33:11 pm »
I've successfully decoded PCIe Gen1 on my (bandwidth-hacked) Tek DPO5034, so don't panic :).
 

Offline Fungus

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Re: Busses, serial links and required scope bandwidth
« Reply #7 on: February 20, 2016, 06:38:25 pm »

That's kind of depressing from a hobby-budget-scope point of view  >:D
Perhaps a list of what you *can* do with a 100MHz or 300MHz scope would be more uplifting?

SPI, I2C, RS232...

(Weirdly enough that's a list of the protocols that are in the menu of my 'scope)
 

Offline Wuerstchenhund

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Re: Busses, serial links and required scope bandwidth
« Reply #8 on: February 21, 2016, 01:09:31 am »
I've successfully decoded PCIe Gen1 on my (bandwidth-hacked) Tek DPO5034.

Decode of PCIe 1.x can work with a 2GHz scope, but that's pretty much it.

It always stroke me as odd that Tek offered PCIe Serial Analysis on a scope series that doesn't even have sufficient bandwidth that's required for it (the DPO5k only goes to 2GHz).
 

Offline Keysight DanielBogdanoff

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Re: Busses, serial links and required scope bandwidth
« Reply #9 on: February 22, 2016, 06:47:09 pm »

That's kind of depressing from a hobby-budget-scope point of view  >:D
Perhaps a list of what you *can* do with a 100MHz or 300MHz scope would be more uplifting?

SPI, I2C, RS232...

(Weirdly enough that's a list of the protocols that are in the menu of my 'scope)

Our InfiniiVision scopes support I2C, SPI, UART (RS232,485, etc), CAN (-dbc), LIN, FlexRay (lol), I2S, MIL-STD1553, ARINC429, SENT

So there's quite a bit you can do with the lower bandwidth scopes.  But once you start getting into high speed digital you're going to have to upgrade.  The list from Wuerstchenhund is (AFAIK) more industry focused and less hobbyist focused.
 

Offline Keysight DanielBogdanoff

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Re: Busses, serial links and required scope bandwidth
« Reply #10 on: February 22, 2016, 06:53:37 pm »
Slide 49 on page 25 is a good reference for this, too.

http://www.keysight.com/upload/cmc_upload/All/Oscilloscope_BW_Reqmts_for_Emerging_Serial_Data_Intfcs.pdf

From an older but interesting talk on optimizing your bandwidth.
 

Offline Wuerstchenhund

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Re: Busses, serial links and required scope bandwidth
« Reply #11 on: February 23, 2016, 06:39:41 am »
Slide 49 on page 25 is a good reference for this, too.

http://www.keysight.com/upload/cmc_upload/All/Oscilloscope_BW_Reqmts_for_Emerging_Serial_Data_Intfcs.pdf

From an older but interesting talk on optimizing your bandwidth.

Thanks for the link, I've added DDR2 and DDR3 to the list.

Funny that it lists SAS 1.5Gbps, as this never was a real standard (SAS Generation 1 is 3Gbps).

Quote
The list from Wuerstchenhund is (AFAIK) more industry focused and less hobbyist focused.

Well, actually it is aimed at hobbyists  ;) These days quite often even hobbyists want to look at stuff like USB2/3, DDR2 and HDMI, and on occasion someone asks for a cheap entry level scope recommendation to do that. The list is meant to be as a guide to show that even measly USB 2.0 is pretty much out of reach of any entry-level (and mid-range) scope (and essentially anything that carries the Rigol logo).
 


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