RE: Purposeful Parity control

["Faria, Dick" <Dick.Faria@compaq.com>]

For the contrived example, the choice seems rather obvious. 
And yes, most reasonable bank computer hardware had better 
implement HW Single Bit (SB) ECC, because crashing a computer
for this reason today is relatively impractical. 

It is hopeful at this end that when PCI-X device adapters
become plentiful in the market,  they will take
advantage of having much more robust and inherent fatal
PERR & SERR built-in recovery. Who knows, maybe some of 
these may even have onboard built-in SB ECC HW as the 
frosting on the fault management cake. This cake is 
becoming computer customer's main course instead
of desert in some industry segments.

 Regards,      

-----Original Message-----
From: Gord Wait [mailto:Gord_Wait@spectrumsignal.com]
Sent: Tuesday, April 17, 2001 5:54 PM
To: 'Dimiter Popoff'; pci-sig@znyx.com
Subject: RE: Purposeful Parity control



	If some hardware deep within your bank's computer suffered a parity
error,
would you rather have it:

	- do nothing, the parity error gets written into the database,
corrupting
	data, eventually causing several problems costing serious time and
effort to
	sort out,
	Or,
	- crash immediately, identifying right now that there is a problem,
and
	exactly which board it came from?

Now I realize this is a contrived example, I would assume the bank uses
error correcting
hardware, but who knows?
Gord Wait


-----Original Message-----
From: Dimiter Popoff [mailto:tgi@bulnet.bg]
Sent: Tuesday, April 17, 2001 2:28 PM
To: pci-sig@znyx.com
Subject: Re: Purposeful Parity control



>> Why was the parity control necessary for a chip-to-chip bus?
>
>For the same reason it's necessary in other reliable, high-speed data
>transfer mechanisms - it is very easy for single bit errors to sneak in, be
>they due to design margin, bad components, external influence, or whatever,
>and without some bandwidth-efficient, cost-effective detection method, a
>single bit error could easily run undetected for a while and worm its way
>into causing system instability.

Do you believe parity check could measurably compensate for
"design margin, bad components, external influence, or whatever" ?
The systems I have seen either work and make no errors so
parity control has nothing to do all the time
or make too many errors and parity control is useless.

Which chip-to-chip PCI based device do you know to recover
from parity error and continue?

What is the typical system behaviour today upon parity error?

Dimiter