Specifications

6.17. Problems with a PAS16 and an Adaptec 1542 SCSI
host adaptor
(the following explanation was supplied by [e-mail])
Linux only recognizes the 1542 at address 330 (default) or 334, and the PAS only allows the MPU−401
emulation at 330. Even when you disable the MPU−401 under software, something still wants to conflict
with the 1542 if it's at its preferred default address. Moving the 1542 to 334 makes everyone happy.
Additionally, both the 1542 and the PAS−16 do 16−bit DMA, so if you sample at 16−bit 44 KHz stereo and
save the file to a SCSI drive hung on the 1542, you're about to have trouble. The DMAs overlap and there
isn't enough time for RAM refresh, so you get the dread ``PARITY ERROR − SYSTEM HALTED'' message,
with no clue to what caused it. It's made worse because a few second−party vendors with QIC−117 tape
drives recommend setting the bus on/off times such that the 1542 is on even longer than normal. Get the
SCSISEL.EXE program from Adaptec's BBS or several places on the internet, and reduce the BUS ON time
or increase the BUS OFF time until the problem goes away, then move it one notch or more further.
SCSISEL changes the EEPROM settings, so it's more permanent than a patch to the DOS driver line in
CONFIG.SYS, and will work if you boot right into Linux (unlike the DOS patch). Next problem solved.
Last problem − the older Symphony chipsets drastically reduced the timing of the I/O cycles to speed up bus
accesses. None of various boards I've played with had any problem with the reduced timing except for the
PAS−16. Media Vision's BBS has SYMPFIX.EXE that's supposed to cure the problem by twiddling a
diagnostic bit in Symphony's bus controller, but it's not a hard guarantee. You may need to:
get the motherboard distributor to replace the older version bus chip, •
replace the motherboard, or •
buy a different brand of sound card. •
Young Microsystems will upgrade the boards they import for around $30 (US); other vendors may be similar
if you can figure out who made or imported the motherboard (good luck). The problem is in ProAudio's bus
interface chip as far as I'm concerned; nobody buys a $120 sound card and sticks it in a 6MHz AT. Most of
them wind up in 25−40MHz 386/486 boxes, and should be able to handle at least 12MHz bus rates if the
chips are designed right. Exit soapbox (stage left).
The first problem depends on the chipset used on your motherboard, what bus speed and other BIOS settings,
and the phase of the moon. The second problem depends on your refresh option setting (hidden or
synchronous), the 1542 DMA rate and (possibly) the bus I/O rate. The third can be determined by calling
Media Vision and asking which flavor of Symphony chip is incompatible with their slow design. Be warned,
though − 3 of 4 techs I talked to were brain damaged. I would be very leery of trusting anything they said
about someone else's hardware, since they didn't even know their own very well.
6.18. Is it possible to read and write samples
simultaneously?
The drivers for some sound cards support full duplex mode. Check the documentation available from 4Front
Technologies for information on how to use it.
The Linux Sound HOWTO
6.17. Problems with a PAS16 and an Adaptec 1542 SCSI host adaptor 22