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From: Peter Brevik <pb@ludd.luth.se>
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Subject: Atapi underrun, too tight wait ?
To: freebsd-hackers@FreeBSD.ORG
Date: Thu, 28 Jan 1999 18:58:07 +0100 (MET)
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    Hi,

I'm trying to read sectors from a atapi cdrom but it seems I get buffer
under run problems. Any ideas on how to solve this ?
I have a suspicion that the CPU is so fast (350 MHz) that it will loop some
delay somewhere. So that it timeout to early..

   /pb

Equipment:

CPU: Pentium II (quarter-micron) (348.49-MHz 686-class CPU)
Origin = "GenuineIntel"  Id = 0x651  Stepping=1
Features=0x183f9ff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,SEP,MTRR,PGE,MCA,CMOV,
<b16>,<b17>,MMX,<b24>>


wdc1 at 0x170-0x177 irq 15 on isa
wdc1: unit 0 (atapi): <COMPAQ  CDR-8335/0008>, removable, accel, dma, iordy
wcd0: 1779/4134Kb/sec, 128Kb cache, audio play, 255 volume levels,
      ejectable tray
wcd0: no disc inside, unlocked
wcd0:  mode 2 form 1(XA) 2, multisession, CD-DA read stream, C2, ISRC, UPC

Problem:

Trying to read sectors from Atapi CD-Rom which results in errors like:
ar.result.code = 6 (data underrun)
ar.result.status = 88 <ready,opdone,drq,>

ar.result.code = 1 (i/o finished with error)
ar.result.status = 81 <ready,opdone,check,>
ar.result.error = 180 <ili,>

ar.result.code = 6 (data underrun)
ar.result.status = 88 <ready,opdone,drq,>

ar.result.code = 1 (i/o finished with error)
ar.result.status = 81 <ready,opdone,check,>
ar.result.error = 180 <ili,>

and so on..
(syslog:  wcd0: i/o error, status=51<ready,opdone,check>, error=b4<abort>)

Kernel:
  2.2.7


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