Serial-Port Hardware/Driver bug - Solaris on non-PCI SPARC workstations:
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The onboard serial ports of most pre-1997 SPARCworkstations are implemented
as a Zilog 8530 SCC UART controlled by the Solaris "zs" driver.

These UARTs only support asynchronous speeds upto 38400 baud.

Unfortunately, if you request a higher speed, the "zs" driver returns
success, even though it can not set such an asyncronous speed.

Many programs expect that a request to set a baud-rate that the
specific serial device cannot handle, will return an error. This is
often used to probe whether a certain baud rate can be used,
on a per-port basis.

Such programs will break when used on zs-controlled ports, because
the "zs" driver lies. slap is one of these programs.

At a guess, the fault in the "zs" driver is that when being asked
to change baud-rate, it is not checking whether the port is set for
async or sync use.

This fault does not bother other serial-ports (SBus plug-in
serial cards, et al).
On all the third-party add-in serial ports I have so far seen,
the driver returns an error if you ask for a baud-rate it cannot do.

The "zs" flaw exists on all versions of Solaris from 2.1 thru 2.5.1.
I have not had the chance to test it on later releases yet, although
I bet it is STILL broken.

Recent SPARC workstations (the PCI-based ones) use Siemens 82532 ESCC
UARTs, controlled by the "se" driver. Because these UARTs have
64-byte input and output FIFO buffers, they should be able to handle
much higher async baud rates. However, do not be surprised if the
"se" driver is capable of lying, too!