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HP 715/75. Is it dead?


New Member
Aug 30, 2023
Hello all, recently I have acquired HP 715/75, and I’m trying to verify it's condition:

- I have checked PSU and all voltages seem to be correct: +5,-5,+12,-12
- I have disconnected EISA graphics card and all SCSI devices. Basically it’s only PSU, mainboard, CPU module, and SIMM’s
- Battery was dead, and i have removed it for the time being (no leakage or anything like that, mainboard is fairly clean)
- When turned on, system shows following LED combinations:
- 1,2,3,4,5,7 ON, which looks like „PDC ROM Checksum error”
- then it immediately goes to 1,6 ON and stays there,
- when TOC button is pressed during power on, it goes from 1,2,3,4,5,7 ON, to 2,5 ON and stays there
- According to system manual, these 1,6 ON and 2,5 ON codes are from ISL, but I doubt the system goes that far, especially that it behaves exactly the same when all of the SIMM’s are removed

Internal display does not display anything, (neither EISA graphics when it was connected)
CPU heatsink is very hot (barely touchable, I think around 90C)
I don’t have a HIL keyboard, so no keyboard was connected during these tests.

Maybe someone has some experience with these machines? Should the heatsink be so hot in 715/75 or is it a bad CPU module?
Anyone have seen such error codes so early in the system startup, even when there is no RAM installed?
According to manual these are ISL codes:
1,6 ON - „Destination memory address of utility is invalid”
2,5 ON - „Error reading autoexec file”

But as I mentioned - when I remove all of the SIMM’s from the machine, codes are exactly the same, and I assume that ISL cannot be executed without RAM present, right?


Experienced Member
Jul 26, 2011
I used some very, very long ago, but really don't recall anything of use. If you have not already looked here the documents they have listed may be of some help.