SCSI problems, hanging SCSI bus

Question (SCSI problems):

I have a big problem. Nothing seems to work. MakeCD or the SCSI bus keep hanging. What can I do about this?

Answer:

Your CD-burner and/or your SCSI host adapter is faulty. Sorry, but we are unable to help you in this instance. Please check our compatibility list -- perhaps you will find a user there with a similar configuration who has managed to resolve the problem. If this doesn't help, try the following -- in test mode!

• Select a small chunk size (32 or 64KB) in the settings window and see it that helps. We have been told that this helps with some Phase 5 host adapters.
• The chunk size plays a major part as to whether hanging occurs with the Philips CDD 2600 (and possibly with other CD-burners). Some people report hanging when the chunk size is too small, but in our experience hanging occurs when the chunk size is too large. You may need to experiment a little here.
• Turn off parallel read/write in the settings window and try testing. If you turn off parallel read/write, the buffer will be constantly almost empty. This is normal but also more dangerous since a buffer underrun is more likely. In this case there is little point in selecting a large buffer. 1MB should be more than sufficient.
• Turn off reselection for all devices, especially for the CD-burner. We have included a small tool with most versions of MakeCDto turn off reselection for Commodore's V39/V40 scsi.device. If this helps, experiment with reselection until you establish which devices can have reselection turned on and which devices must have reselection turned off. If reselection is turned off, the same applies to the buffer behaviour as described above.
• Carsten Schlote (formerly with phase5) has tipped setting the CD-burner to a lower ID number than the hard drive which is being read. This can sometimes help with phase5 hardware and possibly other hardware.
• If nothing helps, try borrowing another host adapter and see if the results are any better when connecting the burner onto its one host adapter. Turn off reselection for the CD-burner, but turn on parallel read/write.

Question (Reselection):

I keep hearing about reselection, the buffer, and so on. What are these?

Answer:

Read the introduction for the chapter on the buffer in the MakeCD instructions.

Questions (Oktagon hangs):

My Oktagon hangs when I read or write audio or mode2 tracks. Will a newer version of the oktagon device help?

Answer:

This problem affects all currently available Oktagon versions ((i. e. up to and including version 6.12). You must turn off reselection for the unit of the CD-burner or CD-ROM drive using the program OktagonPrefs, otherwise the data transfer will only work for tracks with a minimum block size of 2048 bytes. Other sources recommend turning off reselection and synchronous for all devices attached to the Oktagon and setting the chunk size to 256KB. In addition, you should set softXC???oktagon.device as the device driver in place of oktagon.device.

Question (SCSI problems):

I keep getting "buffer underruns" or the SCSI bus hangs. What can I do about this?

Answer (from John Hendrikx <john@globalxs.nl>):

I have experimented with Buffer Underruns with reselection for my CD-burner turned off. The result was that the hard drive could do nothing while the CD-burner used the bus (which can be quite a long time). Turning on selection for my CD-burner and hard drive sometimes led to SCSI errors. However, everything was fine with reselection on for the CD-burner only and not for the hard drive. This hardly affected the speed, since the hard drive (for which reselection has been turned off) does not use the bus for very long anyway. I have successfully burnt CDs at quad speed using the Yamaha CD-burner, although I have an 030 system with 22MHz and only 8MB FastRAM. The data came from an IDE hard drive (I believe that the additional IDE controller simplified the matter somewhat. I was close to the limit using this configuration: one day I had a buffer run - it turned out that I had to run ReOrg over the source drive to make it fast enough again :-) Anyway, a few tips:

• If you think that your hard drive is too slow, try running ReOrg over the hard drive.
• Use large block sizes on your image partitions. I use 2KB blocks on all image partitions (many people use even larger values, but I like to be able to use such partitions as normal partitions too). Fragmented files slow down the hard drive, so small block files sizes are best avoided.
• Check the reselection settings of your SCSI devices. Reselection does not have to be activated for all fast devices (e. g. hard drives), but it probably needs to be turned on for the CD-burner (I have turned off reselection for all my devices apart from the burner -- works brilliantly). If you would like to see the effects of reselection, try the following: turn on parallel read/write; write a large image file to a CD in test mode. Now use a reselection tool and try turning reselection on/off for the CD-burner. As soon as it is turned off, the buffer shrinks. As soon as it is turned on, the buffer fills again in a matter of seconds (this may be different with your configuration - try it anyhow).
• If you suspect that the SCSI host adapter simply isn't fast enough, or if turning on reselection for the CD-burner generates SCSI errors, try using a different SCSI host adapter (a second SCSI adapter or simply an IDE controller). That should work even better, since reselection problems should no longer play a part.

Turning off reselection for your hard drive can actually improve the speed (at least if only one is in use). I measured an almost 20% speed increase with my Seagate hard drive when turning off reselection (it has problems with reselect turned on anyhow -- that was the cause of my hanging SCSI chain, as I eventually found out, not my Yamaha CD-burner.

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