Technical Bulletin

PCI PowerMac Freezing

GCC Printers and Apple Computer share numerous customers that own both Apple PCI Power Macintoshes (7200/75, 7200/90, 7500/100, 8500/120, 9500/120, 9500/132) and GCC high end monochrome laser printers including the SelectPress 600, SelectPress 1200, Elite XL 608, 808, 616, 1208, and 1208 SuperSize.

These customers may experience various type 10 and 11 errors, freezing or crashing when printing to GCC (and other printers). This freezing problem affects only PCI PowerMacs systems, and was not fixed with System 7.5.3 and Open Transport 1.1.

Based on the data that both GCC and Apple has gathered, this is a system level problem that Apple is working to resolve. Apple has reported that this problem affects several vendors besides GCC. Print spooling systems may also be affected.

Both GCC Printers and Apple Computer believes the problem is in system software. There is no evidence that suggests that GCC or any other printer/spooler vendor is at fault. Customers may report that the problem does not happen with Apple-labeled printers, however, this is insufficient evidence to place blame on non-Apple vendors.

Symptoms

Customers will see complete system hangs, application freezing, type 11 or type 10 errors when printing to the following systems:

Windows NT 3.5.1 (even with current service pack updates)

NetWare 4.1
GCC Printers printers including SelectPress 600, SelectPress 1200, Elite XL 608, 808, 616, 1208, and 1208 SuperSize
Brother LocalTalk based printers.

Apple Product support has received reports that of similar problems with other systems, but they have not been confirmed by packet trace at this time.

The chances of this problem occurring is rare, intermittent, and unreproducible.

Rare

The problem occurs in some environments, a specific combination of a Power Macintosh and the printer or server. In a given environment, the problem may happen only on certain model PCI systems (for example 7500/100's crash, but 8500/120's do not), or be specific to a server configuration (a certain model server with a certain model ethernet card), or a specific printer (only a specific model from a vendor causes crashing, other models from the same vendor do not).

Intermittent and unreproducible

Crashes while printing will occur when a Power Macintosh prints to a printer, but crashes cannot be linked to a single file, application, or situation. Printing larger files may have a higher probability of causing crashes than smaller files. This factor has slowed our ability to analyze the problem because customers were unable to record a failed print job in a network trace and we were unable to reproduce the problem until recently.

Models affected:

All PCI PowerMacs (7200/75, 7200/90, 7500/100, 8500/120, 9500/120, 95100/132).

Suggested Workaround

Apple Computer can suggest several workarounds at this time. The source of the problem is timing related, so these workarounds are likely to increase printing reliability, but the improvements are not predictable.

Separate the Macintosh and the printer/spooler with a router.

Two sites have used an Apple Internet Router to fix the problem. GCC reports that most customers have the Macintosh and printer in the same ethernet segment. Segmentation with network routers, bridges, repeaters or software bridges (LocalTalk and LaserWriter Bridge) may also improve reliability.
If printing to a printer, configure and use a print server.

Two sites have used Appleshare Print server to fix the problem. Theoretically, NetWare's ATPS or Windows NT Print Services for Macintosh would have the same function. However, this workaround should be used carefully. AppleShare Print Server on a PCI-based Apple Workgroup Server may exhibit the same problems. Windows NT and Novell NetWare servers also may have problems spooling jobs to the printers listed above.
If printing to a spooler, reconfigure the spooler with a slower network card.

The problem is reproducible in one situation. At the end of a print job, the Macintosh will send an Appletalk ATP TResp that signals "End of Message" (EOM). If the server returns the ATP TRel for the EOM instantaneously, the Macintosh will fail to break down the connection. A packet trace would show the relative time between the TResp and TRel as "0" (less than a millisecond). Most reports of NT problems are on extremely fast PCI based systems.

Replacement of a NIC with a slower performing card, or replacement of the hardware with a ISA or EISA based server may improve reliability by avoiding the "instantaneous TRel".

Apple is working on fixing this problem with a new release of LaserWriter 8. As soon as this new driver is available, GCC will post a link to the driver on our home page under Service and Support.

If you have any questions about this technical bulletin, please contact GCC Tecnical support at (781) 276-8620. Technical Support is also available by fax at (781) 275-1115 and by e-mail at support@gccprinters.com.