Article ID: 151396
Article Last Modified on 11/26/2003
APPLIES TO
- Microsoft Windows NT Server 3.5
- Microsoft Windows NT Server 3.51
- Microsoft SNA Server 2.0, when used with:
- Microsoft SNA Server 2.1, when used with:
- Microsoft SNA Server 3.0, when used with:
- Microsoft SNA Server 2.11 Service Pack 1, when used with:
This article was previously published under Q151396
SYMPTOMS
In certain instances, when you activate an SNA Server SDLC or X.25
connection on an IBM PS/2 computer configured with an IBM MPA/A (or the
Microgate equivalent), the computer freezes and fails to respond to
keyboard or mouse input.
CAUSE
There are two problems which cause this problem to occur:
- The IBM PS/2 abios disk controller tries to allocate all available
map registers for large data transfers. The standard SDLC device driver
allocates 2 when the SDLC connection is activated and never releases
them.
The disk controller hangs while waiting for the map registers. Slowly
the whole system hangs as paging and disk access are stopped.
- The IBM PS/2 abios disk controller performs DMA data transfers at
interrupt processor level. Microsoft Windows NT defines this as
illegal (this may work on a single processor architecture, but in a
multiprocessor environment it is dangerous, so Windows NT disallows it).
The SDLC driver allocates a DMA resource, the disk controller generates
an interrupt, and tries to acquire this DMA resource, and cannot, and
never will be able to (the disk controller has just locked out the
driver that owns it permanently). This causes the system to lock solid.
WORKAROUND
Both problems are solved by applying the alternate Ibmsync.sys driver
(intended for PS/2 computers using the IBM MPA/A adapter or Microgate
Microchannel equivalent), described below. If the default Ibmsync.sys
driver is used, the first problem is solved through the support of a
special DontUseMappedRegisters registry setting for the IBMSYNC driver.
As documented in the SNA Server 2.11 Release Notes (Readme.wri), a special
version of the Ibmsync.sys driver supplied on the SNA Server 2.11 compact
disc can also be used to solve hang problems that may occur on IBM PS/2
computers. To replace the existing driver, start the Windows NT Command
Prompt and enter the following commands:
cd <snaroot>\system
rename ibmsync.sys ibmsync.211
copy <sna_cdrom>:\i386\system\hwsetup\ibmsdlc\ibmsync._sy ibmsync.sys
cd hwsetup\ibmsdlc
rename ibmsync.sys ibmsync.211
copy <sna_cdrom>:\i386\system\hwsetup\ibmsdlc\ibmsync._sy ibmsync.sys
NOTE: The Release Notes document the driver name as ibmsync._ys, though
the actual file name shipped on the SNA Server CD-ROM is ibmsync._sy.
Using the default Ibmsync.sys driver, the following registry setting causes
the driver to not request the use of mapped registers (though this version
of the driver does not correct the other hang problem observed with PS/2
computers).
WARNING: Using Registry Editor incorrectly can cause serious, system-wide
problems that may require you to reinstall Windows NT to correct them.
Microsoft cannot guarantee that any problems resulting from the use of
Registry Editor can be solved. Use this tool at your own risk.
Open Regedt32.exe and locate the following key in the system registry:
HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/IBMSYNC/Parameters
DontUseMapRegisters: REG_DWORD: 1
Once this option is configured, the SNA Server service must be restarted.
STATUS
Additional query words: 2.00 2.10 3.51 prodsna mg96 mg144 dsa usa
Keywords: kbbug KB151396