External Yamaha CD-RW SCSI problem

[physicsGuy]

I have a Yamaha CD-RW external SCSI, the 6416S model, which works fine under OS 9 and Toast.
I didn't try it under OS X until 10.1.5, so I don't know if that "upgrade" has anything to do with this problem. I can't motivate myself to hassle with the "downgrade" to 10.1.4 or lower, to test it.

With Toast Titanium 5.1.3, or with Itunes, or with Disk Copy, if I try to burn a CD-R to anywhere near full (say 550MB on a 650MB disk), I get an error message that the operation couldn't be completed or something (I'll write it down exactly the next time I make a coaster). If I burn just a small amount (and waste a lot of the CD), then it works OK.

Same problem whether an audio CD or a data CD.
Same problem directly from a second CD-ROM drive as a source (only possible with Toast), or from a disk image. So unlikely to be a buffer starve issue due to a slow source.
Just to be sure, I set this 6X drive to 2X. Same problem.

I emphasized SCSI in the title of this post, because I know that OS X's highest priority is not SCSI. It's only from 10.1.3 that they fixed a bug in addressing a whole slew of external SCSI CD-ROMs.

Anyone else with similar problems, and hopefully a fix?

Mac 7500 G3 400MHz xlr8/owc upgrade (an unsupported config)
448MB RAM, OS 10.1.5, Yamaha 6416S in an APS enclosure, with active termination on a downstream APS drive at end of chain. Paperport (for OS 9) is at the beginning of the chain, powered up but not used. Yes, I'll try removing the Paperport scanner, but I doubt that is the problem.

[guillota]

After lot of software updates and patches I found that I had a SCSI cable with wrong connections in pin 17,18,51,52 on the 68pin connector.
This happened me before with a scanner, now I can write CD's under OSX 10.1.5 with Toast 5.1.4 and an external Matsushita 8x Writer!
The correct conections should be:
***50pin > 68pin connector***
12 > NC instead of 17
13 > 17 & 18 instead of 18
37 > NC instead of 51
38 > 51 & 52 & 17 & 18 instead 52
So if you have an external SCSI CD-Writer and when you burn CD's your writer hangs buy a good SCSI cable!!!

[Krevinek]

Actually, I might have a solution, since your machine is the same generation as mine and I have had similar issues with my own Yamaha 8x that we made external ourselves.

There is one big issue with the external SCSI bus on our machines: it has a 5MB/sec theoretical limit. 8x CD burning runs at about 4.2MB/sec. If your computer chokes even a LITTLE, 8x will produce a coaster on me, even 30 seconds into the burn.

Try doing the following things:
- Make sure your cable is up to snuff like the previous poster suggested
- Put it as the SCSI device closest to the machine
- Tell Toast to use a larger RAM buffer (slower caching, but better burns)
- Try not to load your machine down with lots of CPU and/or I/O access while burning. Your bus can easily choke with the graphic data and CD data passing along the bus, you don't need to add more onto that if latency is key, like it is with CD burning.

If you follow these, you should have no problems burning at 6x. Your bus is a little more choked than mine most likely (the 8600 and 9600 had the largest bandwidth ratings out of the G2 series of PowerMacs), but you should be able to do just fine.

[xegan]

I have a SCSI 4x Yamaha burner that has NEVER
burned under ANY version of OSX.

I've been burning since the 0.25x days, so
of course have done all the suggestions
of the prev posts, and then some.

Now, after installing Jaguar, I've had to pull
my SCSI card altogether!!! Won't boot with
it in the machine!! I suspect it has been the
culprit in most of my frequent kernal panics.

Apple hates SCSI and isn't going to do
a damn thing about supporting it. So much
for all my SCSI hardware (zip drive, scanner,
2hds and cd-r).