UNIX pc fan 27CFM vs. 34CFM and 12VDC vs. 120VAC?

[Mike "Ford" Ditto]

In article <401 at icus.UUCP> lenny at icus.UUCP (Lenny Tropiano) writes:
>About 4 months ago I replaced my *DEAD* UNIX pc fan with a Radio Shack
>12VDC 27CFM (cubic feet/minute) 3.5" look-alike.  Back then I didn't have
>any problems, but just recently I'm experiencing sporatic memory parity
>errors.  Diagnostics show nothing, although I think I am attributing it
>to the extreme heat and humidity my bedroom is experiencing.

I have heard many stories of 3b1's dying because of temperature
problems.  When mine was serviced (it was DOA when I got it), the AT&T
technician warned me to make sure the back end of the system was
always given access to air flow (so the fan(s) don't have to work too
hard).  He said he had seen several 3b1's with the top of the case (to
the right side of the monitor) melted down into the power supply.

I would make sure that your system is getting *at least* the amount
of air flow as a normal 3b1.  I have an extra 120V fan sitting in back
of my 3b1 which I turn on during hot weather.  As far as I know, I've
never had any temperature problems.

>A little about my problem and a few questions:
>  ...
>  NMI (parity error) at 0x2FFAC8 (*hpte: 0xE17B) Wed Jun 22 15:00:07 1988
>  NMI (parity error) at 0x84298 (*hpte: 0x412F) Wed Jun 22 17:52:22 1988
>  NMI (parity error) at 0x84298 (*hpte: 0x412F) Wed Jun 22 17:52:28 1988
>  NMI (parity error) at 0x84298 (*hpte: 0x412F) Wed Jun 22 17:53:02 1988
>  NMI (parity error) at 0x82200 (*hpte: 0x4169) Wed Jun 22 19:05:11 1988
>
> [ ... ]
>
>  Boards get very hot, does this effect memory?

It sure can.  It definitely can make a flakey memory chip act up.

>  Addresses vary from low 0x80000 to high 0x2FFFFF (does the lower addresses
>     correspond to physical location of memory or just where the program is
>     at that time which can be on either the motherboard memory or expanded
>     memory?
>  What does "(*hpte: 0x4169), etc..." mean?

Those addresses are the virtual addresses (programs start at 0x80000
on the Unix PC).  The *hpte value is the hardware page table entry,
described in <sys/pte.h>.  You might be interested in the bottom 10
bits (0x169 in this example) which are the physical page number of the
location with the error.  So in this case, it was physical address
0x169000 (part of the second meg of ram on the motherboard).

>  Was the 3B1 original fan a more output (ie. 34CFM) and maybe it is not
>     pulling enough cool air?
>  How does the heat and humidity affect the operation?
>  Will air conditioning alliviate this?

I don't know, but you should definitely look into the fan capacity and
make sure you're not torturing your system.

>  Using the "s4test" expert mode can I run the memory parity test on
>     a particular segement is a "SOAK" mode where I it will run over and
>     over on that test?

I have done this, but it was a long time ago and I don't feel like
rebooting to try it now.  I don't think it even required expert mode.

>  Sort of related question...
>
>  Has anyone tried the 120VAC fan instead of the 12VDC fan and reduce
>     the strain on the power supply?  Does the AC hum interfere with
>     any operation?

I've used an external 120VAC fan as described above, but primarily just to
keep air flowing past the back of the machine.  No ill effects so far.

					-=] Ford [=-

"Once there were parking lots,		(In Real Life:  Mike Ditto)
now it's a peaceful oasis.		ford at kenobi.cts.com
This was a Pizza Hut,			...!sdcsvax!crash!kenobi!ford
now it's all covered with daisies." -- Talking Heads