Re: hard crash despite UPS
2 or 3 years ago I struggled long and hard with an APC UPS on a Linux
system. I finally gave up in disgust and replaced it.
> I have some more info, and it's pretty weird. APC says, and my
> experience seems to confirm it, that you need a different serial cable
> for Unixy systems than Windows. And if you want to dual boot, well,
> that's just too bad.
>
> Unix, they say, is putting a voltage on a pin that the UPS detects and
> takes as a shut down signal. APC says this is a feature for people
> who don't have computers (e.g., you're powering some alarms).
>
> I thought XON/XOFF was hardware flow control...
It is. Usually.
What's happening, I'm pretty sure, is that several years ago APC wanted
a way of communicating between an UPS and a computer. Since those DB9
serial ports were so handy on the back of DOS machines, they decided to
use those. But since the information they had to communicate was simply
a few ON/OFF states (and microprocessors were expensive back then), they
used the RS232 modem state lines. And, like Pigeon says, Linux and
Windows initialize the states of those lines differently. Therefore APC
UPSes don't work right with Linux without some (significant for some
people) hardware futzing to set the serial ports 'right.'
And there's the business of the special APC serial cable. I never fully
understood about that, but from talking to APC, it sounded like there
needs to be an oddly wired cable between the UPS and the computer. I was
told there should have been one included with the UPS, but there wasn't.
I looked for the schematic, and finally found it, but it was illegible.
There are manufacturers that use the RS232 connectors for serial
communication. Mine are Tripplite. The APC solution works great with
Windows, but I'm not running Windows...
Yet another, IMHO, proprietary standards-busting system.
--
Glenn English
ghe@slsware.com
Reply to: