[ibm-pc] Opravdu vyrobci takto likviduji ECC?

["totojepast" <totojepast zavinac atlas bod cz>]

http://cr.yp.to/hardware/ecc.html
Memory errors and SECDED
According to memory manufacturer Corsair, a typical computer with 256MB
of non-ECC memory has several memory errors every year. These hardware
failures cause computers to crash, destroy data, etc.

ECC memory, when properly used, eliminates this problem. It stores 64
bits of data in 72 bits of physical memory using what mathematicians
call a ``distance-4 code.'' If one of those 72 bits is flipped by a
cosmic ray, the motherboard will automatically fix the error, letting
the computer continue operating with the correct data. In the unlikely
event that two bits are flipped, the motherboard will at least detect
the error and halt the computer, rather than allowing data to be
corrupted.

(Of course, software failures also cause computers to crash, destroy
data, etc. In a world of ludicrously fragile 20th-century software
design, software failures are extremely common, and most hardware
failures are incorrectly blamed on software. Making computers work
means making the hardware work and making the software work.)

Error correction is not free. ECC memory is inherently 72/64=1.125
times as expensive as non-ECC memory; it uses 9 memory chips where
non-ECC memory uses 8. However, given the fact that one can buy 512
megabytes of Kingston ECC memory for under $100 as of October 2001, it
seems rather silly to worry about this difference.

A more serious problem is the circuitry required for the motherboard to
actually correct errors. This isn't expensive to build, but it requires
engineering expertise that, apparently, most hardware manufacturers
don't have.

Abit, for example, produces motherboards that don't actually correct
errors, although you can still plug ECC memory into them. Even worse,
Abit habitually makes fraudulent claims of ECC support. I will never
buy another Abit motherboard.

The Linux ECC page has a list of chipsets that can correct errors.
Note, however, that many motherboards don't actually correct errors,
even though they use chipsets capable of correcting errors; the Asus
A7M266 motherboard, using the AMD 761 chipset, is an example.

If you're a motherboard manufacturer, and you have a motherboard that
actually corrects errors, please say so! This is a major plus for your
motherboard. Don't just say ``ECC'' in your data sheets. Say ``SECDED:
corrects single-bit RAM errors, detects double-bit RAM errors.'' SECDED
is a standard acronym for single-error correction and double-error
detection.

If you're a computer purchaser, feel free to copy this link to your web
pages: I buy PCs with SECDED.


http://cr.yp.to/hardware/abit.html
Why I will never buy another Abit motherboard
In 2000-07, when I was buying my first Athlon, I heard about a serious
bug in the Asus K7V BIOS: the K7V wouldn't boot when ECC was enabled.
So I bought an Abit KA7 instead. This was a serious mistake. Abit
habitually makes fraudulent claims of ECC support. This page gives some
examples.

At the beginning of 2001-03, I sent technical zavinac abit-usa bod com a 
pointer to
this page, and asked for their comments. They did not respond.
KA7
Abit's announcement of the KA7 claimed that the KA7 ``supports ECC.''
As of 2001-02, Abit's web pages continue to claim that the KA7
``supports ECC.'' The KA7 BIOS has an ECC option. [local copy of
www.abit.com.tw/english/press/2000/press27.htm, 2001-02-27] [local copy
of www.abit.com.tw/english/press/2000/press72.htm, 2001-02-27] [local
copy of www.abit.com.tw/english/product/motherboards/ka7.htm,
2001-02-27] [local copy of
www.abit.com.tw/english/product/motherboards/ka7-100.htm, 2001-02-27]

In fact, according to Peter Heckert, the KA7's ECC option does not
support error correction; it merely looks for ECC memory.
KT7
``The Abit web site,
http://www.abit.com.tw/english/product/kt7-raid.htm, says: "Supports
ECC",'' Andrew E. Schulman (andrex zavinac zzapp bod org) said in a 2000-10-04
16:01:02 PST posting to comp.sys.ibm.pc.hardware.systems. ``I bought a
kt-7 raid because on the site it stated: ECC Support !'' Roderick den
Haring (hatex zavinac planet bod nl) said in a 2001-01-08 posting to
alt.comp.periphs.mainboard.abit.

In fact, the KT7 doesn't support ECC. ``According to our KT7 designer,
the ECC function is non-functional,'' TechSupport zavinac ABIT
(support zavinac server2 bod abit bod com bod tw) said in a 2000-08-17 20:15:37 
PST posting
to alt.comp.periphs.mainboard.abit. ``We're planning to remove this
option in future BIOS releases.''
VP6
Abit's original specifications for the VP6 claimed that the VP6
``supports ECC.'' As of 2001-02, some of Abit's web pages continue to
claim that the VP6 ``supports ECC.'' Resellers are continuing to repeat
this information; for example, Micro X-Press's web pages say that the
VP6 ``Supports ECC.'' [local copy of
www.abit.nl/english/product/motherboards/vp6.htm, 2001-02-27]

In fact, the VP6 does not support ECC. ``VP6(BIOS: UR) does not support
ECC memory module,'' the Abit FAQ says. According to Peter Seebach, the
new manual says that the VP6 ECC option ``checks whether the memory
installed is ECC.''