TABLE OF CONTENTS
USB 2.0 vs USB 3.0
Important
- SIRIUS CD & HS devices use USB 2.0 connection only.
- Connecting SIRIUS CD & HS devices to USB 3.0 capable port DOES NOT increase bandwidth (see 1.)
- SIRIUS CD & HS devices connected to external USB 3.0 capable HUB will operate with USB 2.0 bandwidth limitations (see 1.)
- USB 3.0 connections can be used for super-speed data transfer (External memory, Flash storage, SIRIUS-XHS...)
SBOXe
Standalone unit.
SBOXe front panel USB Tree
| Position | USB 2.0 Bandwidth | USB 3.0 |
Top Left Port | 24 - 28 MB/s | Available |
Top Right Port | 24 - 28 MB/s | Available |
| Bottom Left Port | 24 - 28 MB/s | Available |
| Bottom Right Port | 24 - 28 MB/s | Available |
Back panel USB Tree
| Position | USB 2.0 Bandwidth | USB 3.0 |
Top Port | 24 - 28 MB/s | No |
Top Port | 24 - 28 MB/s | No |
Notes:
- SIRIUS slices use only USB 2.0 connections.
- USB 3.0 connections can be used for super-speed data transfer (External memory, Flash storage,...)
- CONCLUSION: All USB 2.0 ports were designed for full bandwidth requirements of SIRIUS-HS slices.
SIRIUS R8, SBOXre
PC platform used in:
- R8
SBOXre front panel USB, combination #1
| Position | USB 2.0 Bandwidth | USB 3.0 |
Top Left Port | 24 - 28 MB/s | Available |
| Bottom Left Port | 24 - 28 MB/s | Available |
SBOXre front panel USB, combination #2
| Position | USB 2.0 Bandwidth | USB 3.0 |
Top Right Port | 24 - 28 MB/s | Available |
| Bottom Right Port | 24 - 28 MB/s | Available |
Notes:
- Due to design limitations (limitations of COMe CPU module PCIe lines for USB root HUBs) USB ports share resources and BW.
- CONCLUSION: Avoid connection to two top ports or two bottom ports simultaneously.
R8D / R8DB display panel USB Tree
| Position | USB 2.0 Bandwidth | USB 3.0 |
Left Port | Limited if Center Port is used | Available |
Second Port (from left) | 24 - 28 MB/s | Available |
| Third Port (from left) | 24 - 28 MB/s | Available |
| Right Port | 24 - 28 MB/s | No |
SIRIUS Rack slices USB
| Internal Rack slices (8x slice) | Bandwidth |
| USB 2.0 | 24 - 28 MB/s |
Notes:
- SIRIUS slices use only USB 2.0 connections.
- USB 3.0 connections can be used for super-speed data transfer (External memory, Flash storage,...)
- CONCLUSION:
- Internal SIRIUS slices USB connections are designed for maximum performance.
- Due to design limitations (limitations of COMe CPU module PCIe lines for USB root HUBs) front USB ports share resources and BW.
SIRIUS R1/R2/R4, SBOXse
PC platform used in:
- R1DB
- R2DB
- R4
SBOXse front panel USB
| Position | USB 2.0 Bandwidth | USB 3.0 |
Top Left Port | 24 - 28 MB/s | Available |
Top Right Port | 24 - 28 MB/s | Available |
| Bottom Left Port | 24 - 28 MB/s | Available |
| Bottom Right Port | 24 - 28 MB/s | Available |
SIRIUS Rack slices USB
| Internal Rack slices (1, 2 or 4x slice) | Bandwidth |
| USB 2.0 | 24 - 28 MB/s |
Notes:
- SIRIUS slices use only USB 2.0 connections.
- For optimal and maximum performance of all 4 USB ports additional USB root hubs are installed.
- USB 3.0 connections can be used for super-speed data transfer (External memory, Flash storage,...)
- CONCLUSION: All USB 2.0 ports were designed for full bandwidth requirements of SIRIUS-HS slices.
USB Bandwidth calculation
Dewesoft Calculator 1.5
Dewesoft calculator is a simple tool that calculates USB transfer (MB/s) for various Dewesoft devices.
https://download.dewesoft.com/download-file/dewesoft-calculator-15zip
Background
AI channels
SIRIUS-HS will transfer 2 Bytes of data per each sample per AI channel.
Calculated Bandwidth:
= 2 B/Sample * Sample Rate * nr. of active channels
= 2 B/S * 1 MS/s * 8 channels
= 16 MB/s
Counter channels
SIRIUS-HS will transfer 8 Bytes of data per each sample per CNT channel.
Calculated Bandwidth:
= 8 B/Sample * Sample Rate * nr. of active channels
= 8 B/S * 1 MS/s * 1 channels
= 8 MB/s
Measurements
Upper limit
Although that up to 32 MB/s was actually possible to transfer via single USB connection with 2x SIRIUS-HS slice in a R4-HUB system this is considered to be a top limit. In many cases connection speed proved to be unstable with several host computers.
By experience like seen in the calculator itself 28 .. 29 MB/s transfer rate via single USB connection was operational without problems (for AI channels only, read below!)
AI & CNT @ 1MS/s (SIRIUS-HS)
| Config | BW (MB/s) | Comment |
| 8 x AI | 16 | Normal and no issues at all |
| 8 x AI 1 x CNT | 24 | Normal and no issues for units in production, older designs of SBOX computers suffered problems with USB Non-Native HUB BW. |
| 14 x AI | 28 | Reaching top limit but considered stable. |
| 6 x AI 2 x CNT | 28 | Although that BW is exactly the same as in above case, CNT channels are processed differently as AI channels and this configuration will not run stable in many cases. |
| 8 x AI 2 x CNT | 32 | Will not run, USB buffer overflow. |
Jernej Kovačič, 20.4.2023