HP Designjet T7200

1. Escalate the issue to the GBU through the GCC in order to have it corrected in the firmware.
2. Recommend to customers that they try to avoid the same steps to avoid the error.
3. If the conditions that cause the error are in the customer’s regular workflow, try to identify a different
way of achieving the same result.
Random SE 79:04 (memory leaks and concurrence issues)
Some 79:04 errors can happen randomly when the printer is heavily used. However, it’s impossible to find a
single set of conditions that reproduce the problem. It just happens from time to time, without a defined
pattern.
These random 79:04 errors can have two different types of root causes.
●
Memory leaks: Before a program is executed, it allocates the memory it will need. After the execution is
complete, the allocated memory is freed to be used by other programs. If the allocation or the release
of the memory are not properly programmed, every time the program is executed some memory will be
incorrectly labelled (either as used or as free). This is known as a memory leak. When a program with a
memory leak is executed a lot, the memory becomes progressively full (since it is not properly freed).
When the leak becomes too big, the printer is left ‘out of memory’ to execute new processes and a
79:04 is triggered.
●
Concurrence issues: There are certain resources that can be accessed by multiple programs or by
multiple executions of the same program (what is known as multiple threads). Access to these
resources must be correctly controlled to prevent unexpected behavior. Issues caused by incorrect
control of these resources are concurrence issues.
For example, imagine that there is a counter that controls the communication between the Jetdirect card and
the printer’s firmware. Whenever a new packet of information is sent by the Jetdirect card to the printer, the
counter increases. When the printer receives the packet and processes it correctly, the counter decreases.
Another process checks the counter from time to time to see its value and draw conclusions from it. If the
counter is near 0, it means that the printer is processing correctly, and if it grows too large, it may mean that
there is a bottleneck somewhere and maybe the Jetdirect card throughput is decreased to control its speed
to the printer. However, if the access to this counter is not properly controlled, undesirable effects may
happen: in a real environment, a Jetdirect card processes thousands of information packets per second, so
this counter is updated frequently, both by the Jetdirect and the printer. If at a certain point the Jetdirect card
and the printer try to access the counter at the same time and the code is not prepared to handle this, it may
happen that the Jetdirect cannot increase the counter because the printer is writing to it, and what’s worse, it
does not realize this fact. If this happens a few times each second, it may happen that the counter is
decreasing faster than it’s increasing and that at a certain point it has a negative value. And then, what will
the process that is checking this counter do? Most likely, the process will not be prepared to react to a
negative value and will launch an exception that will trigger a 79:04 system error.
Cause
This type of 79:04 error always occurs in heavy load conditions, so the symptoms will normally follow this
pattern.
●
A printer that is heavily used (printing a project or in a reprographics environment) produces 79:04
errors randomly, forcing the user to restart.
●
After restarting, the printer can be used without any issues for an extended period of time, but if the
workload is consistently high a random error will occur again.
●
The error can never be associated with a specific file. The file that was being printed when the error last
occurred can be printed without issues after restart. And a file that has been printed without issues
several times can trigger the error in the future.
●
This error is very dependent on the customer's workflow. The most common user workflows have been
extensively tested both by HP and by our beta sites, so random 79:04 issues are most unlikely to occur
ENWW How to troubleshoot the 79:04 system error 29