I have a piece of computer hardware in my lab that is running an Intel Celeron CPU with 300 MHz and 128k bytes of secondary cache. The hardware documentation says it's running an real time operating system (RTOS) called pSOS (Portable Software On Silicon). I wanted to measure what is the load on the CPU to know if I can load more stuff into it.

Because this is legacy hardware, I am having a hard time trying to find any information or guide on how to measure CPU usage for this chip.

My best guess is that I can do that using TELNET and the correct command to read CPU usage and memory allocation. I can already TELNET to the CPU and by using the help command I get a list of commands. The problem is, I have no idea what is the exact command I have to type in order to read that kind of info. And I am afraid to mess up the CPU.


This OS don't support uname nor top commands.

But it does support arp, netstat, ifconfig.

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    Do you know what OS it's running? Or could you post a transcript of your Telnet session? (Make sure IP addresses, usernames and passwords are redacted.) Alternatively, your DHCP server might give you a clue what it's running, or run nmap -O -sV from a Linux machine to tell you what OS is running on Jan 18, 2018 at 20:54
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    Measuring CPU usage is an aspect of the operating system. In a general sense, unless the CPU is actually "asleep" (which is a hardware state), the "CPU usage" is always "100%". What the operating system measures is how of the CPU is doing something BESIDES spinning idle waiting for an interrupt by an external device or timer. But "spinning idle" is, well "CPU usage". So, short story, it's up to your operating system, to answer this. This is not (typically) a hardware problem. Jan 18, 2018 at 22:38
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    Hey everyone, OS type identified. It is caled pSOS.
    – FTM
    Jan 19, 2018 at 10:26
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    I was about to challenge that this question fits here - But, as psos+ has been discontinued 19 years ago, we probably need to accept this question. I wasn't even aware psos would run on Intel. Only knew it to be supporting 68000
    – tofro
    Jan 19, 2018 at 10:34
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    can you post the output of “help”? Jan 20, 2018 at 11:32

2 Answers 2


Apparently, you're ending up in psh, the pSos+ shell.

Note what you have is an embedded system that is completely customized - So what you can and cannot do is entirely depending on what the system builder wanted you to be able to do.

psh+ manual (for PowerPCS, but I'd assume Intel is similar) can be found here:


(starting from pg. 1-114) Just browsed this shortly to find some sort of system load indicators, but a quick glance did not reveal anything.

System load information can only be retrieved if the realtime kernel actually collects it - And in the case of PSos, I'm afraid it doesn't. So, no luck.

  • Hello @tofro, I also found this manual a few minutes ago. And I am also getting to the same conclusion, that it will probably not be possible to retrieve that info...
    – FTM
    Jan 19, 2018 at 11:12

As others have pointed out, knowing what OS is running is really the key. help as a valid command could be any variant of *nix, but also many other operating systems and even an application that is processing the telnet command instead of an OS shell process. But assuming it is some variant of Linux or a similar OS, try the top command. The options vary, but typically it starts off running showing the "biggest" programs at the top sorted either by memory usage or CPU usage. It also lists some overall system information, such as total memory available and total memory used. The specifics vary a bit by OS version.

One other item that would be helpful to figure out system capacity is the memory. You mentioned 300 Mhz. (speed) and 128k secondary cache, but not the amount of total system RAM. A quick search shows system of that vintage with 32 - 64 Meg., but I wouldn't be surprised to see quite a range from "single task" systems with less to top-of-the-line servers with much more, though Celeron has always been on the budget side so this was probably never a top-of-the-line server.

  • The scarce and really bad quality documentation we have about this hardware says it has "32 to 256 Mbytes Synchronous DRAM with parity / ECC". So, I see that my first task is to discover which OS is running in this hardware. How could I do that?
    – FTM
    Jan 19, 2018 at 7:06
  • @FTM - Lots of unknowns. But basically you start with whatever works. For example, if the top command works that my give you some clues. What does the help command tell you? What is the initial prompt when you log in via telnet? Jan 19, 2018 at 7:12
  • unfortunately lots of them. I just tried it out using TELNET and it says that both top and uname are unknown commands. When I log in using TELNET, the only message I get back is "Welcome to Telnet Shell session".
    – FTM
    Jan 19, 2018 at 7:42
  • @FTM what about any other common *nix command? I'd try echo, set, cd, pwd, ls and, just in case it runs any MSDOS derivative, dir. Jan 19, 2018 at 8:07
  • both uname and top are external commands. just because the shell doesn't find them doesn't mean it's not a unix/linux/minix machine, perhaps they've been removed from /bin (or /usr/bin), or you don't have a $PATH set to there. what does ls -lR / show ?
    – Tommylee2k
    Jan 19, 2018 at 8:27

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