All UltraFast cards have two operating modes: FIFO mode or Standard mode.
UF2
(PCI-X)
UF
(PCI)
Max theoretical bus transfer speed
264 MB/s
132 MB/s
Reached max transfer speed, 33MHz PCI
115 MB/s
105 MB/s
Reached max transfer speed, 66MHz PCI-X
230 MB/s
105 MB/s
Record / Replay longer signals...
The FIFO mode is a standard feature that allows recorded
or generated signals to be transferred continuously between the UltraFast board
and the PC RAM or hard disk. It is especially useful to record or replay signals longer than the available onboard card memory. However, this is limited by the available PCI or PCI-X bus data transfer rate.
The data transfer rate of the PCI bus limits the FIFO performance to approximately
100 MB/s between the UF card memory and the PC's RAM. This rate is increased to approx. 200MB/s for the new UF2 cards that use the PCI-X 66MHz/32-bit PCI bus.
Limitations
The choice of operating
system, other peripherals using the PCI bus at the same time, and any other running applications can reduce these rates. Please note these ratings are only possible using a small c/c++ or Delphi program (examples are supplied with the cards). Using LabVIEW, MATLAB or other programs will reduce the rate to approx. 20 MB/s as these programs are not optimized for fast transfer rates.
To/from hard disk(s)
When streaming to or from a single hard disk, the maximum data transfer rate is approximately
25 - 50 MB/s. This performance is greatly affected by the hard disk speed, disk cache
memory size and choice of operating system. It is strongly recommended that anti-virus,
power save and other running applications that cause random hard disk accesses
are turned off. Furthermore, the hard disk must be regularly defragmented and
it is advisable to use a second hard disk for the measurement or signal generation
data.
The performance of hard disk streaming can be further improved by using advanced
disk controller technologies such as RAID arrays. Using a RAID controller with four S-ATA hard disks it is possible to stream at up to 200 MBytes/s.
Calculating the data transfer rate
We will assume that the user wishes to use the FIFO mode to stream recorded data
to the PC's RAM.
PCI
PCI-X (UF2)
Maximum PCI bus rate is : ~ 80 MBytes/s
Signal will be recorded by a 12-bit A/D card,
each sample will generate 2 Bytes of data
Therefore up to 40 MSamples / second can be transferred to the PC
e.g.
- 4 signals can be recorded at 10 MS/s sample rate
- 2 signals can be recorded at 20 MS/s sample rate
- 1 signal can be recorded at 40 MS/s sample rate
Maximum PCI-X bus rate is : ~ 200 MBytes/s
Signal will be recorded by a 12-bit A/D card,
each sample will generate 2 Bytes of data
Therefore up to 100 MSamples / second can be transferred to the PC
e.g.
- 4 signals can be recorded at 25 MS/s sample rate
- 2 signals can be recorded at 50 MS/s sample rate
- 1 signal can be recorded at 100 MS/s sample rate
It is obvious from these calculations that the highest sampling rates can only
be achieved when the FIFO mode is not used, but instead the signals are stored
to the onboard signal memory using Standard Mode that is similar to a Digital
Storage Oscilloscope. The data can then only be downloaded from the card at the end of the measurement - allbeit at 100 or 200 MB/s depending on UF/UF2 card used.
If you attempt to use the FIFO mode when recording or generating signals beyond
the achievable transfer rates a FIFO buffer overrun error will occur. A free software utility called 'speed.exe' is available on request for customers wishing to measure the PCI transfer rate performance of their own system (it requires a UF/UF2 card to be installed, Windows only).
