EPOX nVIDIA nForce3 250Gb Manuel d'utilisateur télécharger pdf (Page 7)

Typically you would invoke ’./wr’ as follows:

./wr 80000 10000 2 0 0 0 1 /i1/t/test-%05d 5000 < vsib

This would record the 16 least signiﬁcant bits of VSI at full clock rate into two ﬁles,

/i1/t/test-00000 and /i1/t/test-00001, 5000*80000=400000000 bytes each. The to-

tal duration of this recording would be 12.5 seconds. Please note that ’./wr’ ex-

pects the name of the VSIB device ﬁle as its standard input, otherwise it will com-

plain “standard I/O is not an VSIB board”.

3.5 VSIB Board Modes

The VSIB 4-bit “mode” register is documented in ’proj/vsib/docs/modes.txt’ and

the following modes have been deﬁned in VSIB/R recording Xilinx ﬁrmware.

all32bits: "0000"; -- MK5 32-bit mode, all the VSI data

even16bits: "0001"; -- MK5 16-bit mode or all sign bits from VLBA sampler

low16bits: "0010"; -- alt: 2-bit USB from 8 BBCs

-- norm: 2-bit USB+LSB from 4 BBCs

-- also S2 16-bitstream mode

low8bits: "0011"; -- alt: 2-bit USB from 4 BBC:s

-- norm: 2-bit USB+LSB from 2 BBCs

loweven8bits: "0100"; -- MK5 8-bit mode or 8 sign bits from VLBA sampler

-- alt: 1-bit USB from 8 BBCs

-- norm: 1-bit USB+LSB from 4 BBCs

autoc4x2bits: "0101"; -- as ’low8bits’; Autocorrelator 2-bit mode

autoc4x1bit: "0110"; -- 4-bit low even; Autocorrelator 1-bit mode

test2bits: "0111"; -- 2-bit mode for test

test1bit: "1000"; -- 1-bit mode for test

VLBA_142: "1001"; -- VLBA 1:4 fanout mode with 2-bit sampling

VLBA_141: "1010"; -- VLBA 1:4 fanout mode with 1-bit sampling

VLBA_122: "1011"; -- VLBA 1:2 fanout mode with 2-bit sampling

VLBA_121: "1100"; -- VLBA 1:2 fanout mode with 1-bit sampling

VLBA_112: "1101"; -- VLBA 1:1 fanout mode with 2-bit sampling

Of these, the modes 0 (“all32bits”) and 2 (“low16bits”) are probably the most useful

for testing VSI-H DOMs.

When you try to use the mode 0 to capture all 32 bit streams of VSI you will have to

use “skip=1” to halve the VSI clock to 16 MHz and capture effectively every other

word when using just one VSIB PC. Although VSIB will manage up to 800 Mbps

in a nForce3 PC, the PCI32/33 bus just cannot sustain full 1024 Mbps and the back

panel LED number 4 (PCI FIFO overﬂow) will light up.

3.6 Delayed / Timed Start

It is often desirable to be able to start VSIB capturing at a given UTC time. For this

you need to ensure that the PC gets its time from a “good enough” (within 0.1 sec-

ond) NTP time server. You should change ntpd conﬁguration to point to your local

NTP time server. It is easiest to do this (as root) with ’dpkg-reconﬁgure ntp-simple’

which will update both ’/etc/ntp.conf’ and ’/etc/default/ntp-servers’ consistently.

After updating the ﬁles you can ’/etc/init.d/ntp stop’, ’/etc/init.d/ntpdate start’,

’/etc/init.d/ntp start’ and wait for about 5–10 minutes for the ntpd to gain sync,

but it is probably easiest to just reboot with ctrl-alt-del. Oops, I have forgotten the

’/etc/init.d/ntpdate’ script in disabled state, it is now called ’/etc/init.d/ntpdate.not-

in-csc’, so please rename/’mv’ it back to ’/etc/init.d/ntpdate’. (’ntpdate’ gets the

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EPOX nVIDIA nForce3 250Gb Manuel d'utilisateur Page 7

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