🚀 go-pugleaf

In <1992Nov02.215953.23041@kksys.com> gk@kksys.com (Greg Kemnitz) writes:

>One -- NONE of the manufacturers whose products we handle recommends the use
>of such a device on any of their 386, 486SX or 486DX products, excepting the
>486DX/50 localbus products.

>Five -- If you will look closely at what I wrote, I said that we have found
>that MOST 486 cpus do not require this type of device.  I never said ALL,
>and in fact did describe one case where we have found them to be desirable.

Well, Greg, it's really hard to comment on what you wrote. Especially since
your tone changes so much from point to point.

I thought I'd actually throw some FACTS into this flame war. Doesn't anybody
who pontificates on the net actually READ a datasheet anymore???

I only have June 1991 Intel info for the 486. Order Number: 240440-004. If you
all are as intimately involved in the PC business as you claim to be, you will
have more current info, but it probably won't be much different.

Intel has provided a chart for the maximum allowed temperature for the 486,
with and without a "typical" heatsink. I've studied this chart. Have any of
you guys???

Table 13.3 Maximum ambient temperature at various Airflows in degrees C
---------------------------------------------------
                     fCLK  |   Airflow in ft/minute
                      MHz  |   0       200      400
---------------------------------------------------
with heat sink       25.0  |  47        64       71
                     33.3  |  36        58       67
                     50.0  |  35        60       70
---------------------------------------------------
without heat sink    25.0  |  31        40       47
                     33.3  |  15        27       36
                     50.0  |  10        22.5     32.5
---------------------------------------------------

For those of you who don't do Celsius <--> Fahrenheit conversions in your head,
recall that 20 C is 68 F, and 30 C is 86 F.

It's clear to me that the 33 or 50 MHz 486 in virtually ANY office environment
requires a heat sink. Cheap cloners who don't supply one are saving a few
dollars at the expense of "flakies" and long term reliability.

For example, at 200 fpm airflow, the 33 MHz chip is only rated for 27 C. This
is only 80 F. Doesn't the air in your office ever get that warm in the summer?
Are you sure that the CPU is getting ANY airflow over it, given the poor
location of fans in many boxes, and the long expansion cards, and the rats
nests of ribbon cables, etc, etc, etc?

>Two -- We have NEVER seen a system fail in service due to a processor chip
>failure.  This is despite having sold many many hundreds of systems.  Our
>customers are in general long term customers, and most of our business is
>repeat business, so we have the opportunity to track the history of the
>systems we have sold.  We also service a large number of systems sold by
>others, many with substandard cooling, and have never seen a failed cpu chip
>in them either.

This is an incredibly pompous statement, and displays gross ignorance of the
temperature related failure modes of these chips.

First, failures typically are "soft". The part fails at high temperature and
when it is cooled starts working again. This sort of flakiness is often seen
in computer systems that are returned for service but "no problem found".

Second, failures typically are in "worst case" paths. These paths depend on
both voltage and temperature. 99+% of the chip may be working, but one or two
instructions or cache locations may be flaky. You think your computer works,
but it's not QUITE working.

Third, much of the reason for the conservative temperature ratings Intel places
on their chips has to do with LONG TERM reliability. There are phenomena like
electromigration that cause cumulative damage long term, and not immediate
failures.

But then again, I guess that long term failure doesn't matter much anymore.
The PC business is moving so fast that a five-year-old computer that was
state-of-the-art then is almost worthless now.