watermaa@boulder.Colorado.EDU (WATERMAN ALEXANDER S) (03/27/90)
I have yet another question !
I'm looking at the University price list and see the choices avail. for the fx.
What is the difference between a IIfx, 80 HD, 4meg and a
IIfx, 80 HD, parity/4meg ?
Is it worth the extra $450 for this feature?
Thanks in advance for your help !
Kent Leung
watermaa@boulder.colorado.edu (internet)
Posted c/o A. Watermanmeuchen@grad2.cis.upenn.edu (Paul Eric Menchen) (03/27/90)
In article <18876@boulder.Colorado.EDU> watermaa@tramp.Colorado.EDU (WATERMAN ALEXANDER S) writes: ... >I'm looking at the University price list and see the choices avail. for the fx. > >What is the difference between a IIfx, 80 HD, 4meg and a > IIfx, 80 HD, parity/4meg ? > >Is it worth the extra $450 for this feature? > >Thanks in advance for your help ! > >Kent Leung >watermaa@boulder.colorado.edu (internet) >Posted c/o A. Waterman Of course this is just my $0.02 worth: First, the extra $450 is for parity checking hardware and parity SIMMs. To answer your question: Do you use parity checking for your modem transmissions or 8-N? Given the choice you would probably want no parity. Most poeple have now agreed that parity is a bad way to check for errors. Have you ever had a memory error, besides the power being turned off? I doubt it. As I've heard it explained, parity checking was added to meet a government requirement for DoD type purchases. Why did the gov. decide parity was good? IBM demonstrated how great it was to them. The fed's said, yes, we want parity. They created their bid specs, and guess who turned out to have the only parity machines at the time :^) Paul Eric Menchen meuchen@grad1.cis.upenn.edu
jrg@Apple.COM (John R. Galloway Jr.) (03/27/90)
In article <22291@netnews.upenn.edu> meuchen@grad1.cis.upenn.edu (Paul Eric Menchen) writes: >In article <18876@boulder.Colorado.EDU> watermaa@tramp.Colorado.EDU (WATERMAN ALEXANDER S) writes: >> >>Is it [parity] worth the extra $450 for this feature? >> >>Kent Leung >Do you use parity checking for your modem transmissions or 8-N? >Given the choice you would probably want no parity. Most poeple have >now agreed that parity is a bad way to check for errors. Have you ever >had a memory error, besides the power being turned off? I doubt it. I suspect your are right (as you state later) that it was for gov bids. But your analogy seems syspect. If you are running any sort of file xfer on your modem, then there IS error checking on a block basis at the higher level. If runing interactively you will (or at least can) see the error when a character is echoed incorrectly. But there is no higher level when you load and execute a program or load a database. Would you turn ERCC checking off on your disk? Likey not (even if you could). I have seen parity errors, very rarely but it seems like cheap protection especially if you are using your machine for vital informaiton (like your accounts or checkbook etc.). I would rather have a longer ECC code on longer data (i.e. on a 32/64/128 bit item) but if parity is all I can get, I think I would tend to take it. ALso parity errors become more likely as DRAMs get denser and hence the bit cell holds fewer electrons and is more easily flipped. Perhaps the best solution are DRAMs (available I think) that have internal error detection and correction. That way the only part of the system that has to worry about the issue, is that which is most vulnerable, and the rest need not be concerned. I am POed that Apple bundled the parity option with the 80SC, so you can't get a diskless IIfx with parity. -jrg -- internet jrg@apple.com John R. Galloway, Jr. applelink d3413 CEO..receptionist 795 Beaver Creek Way human (408) 259-2490 Galloway Research San Jose, CA 95133 These are my views, NOT Apple's, I am a GUEST here, not an employee!!
fiddler@concertina.Sun.COM (Steve Hix) (03/28/90)
In article <39856@apple.Apple.COM>, jrg@Apple.COM (John R. Galloway Jr.) writes: > In article <22291@netnews.upenn.edu> meuchen@grad1.cis.upenn.edu (Paul Eric Menchen) writes: > >In article <18876@boulder.Colorado.EDU> watermaa@tramp.Colorado.EDU (WATERMAN ALEXANDER S) writes: > >>Is it [parity] worth the extra $450 for this feature? > >Given the choice you would probably want no parity. Most poeple have > >now agreed that parity is a bad way to check for errors. Have you ever > >had a memory error, besides the power being turned off? I doubt it. > > I suspect your are right (as you state later) that it was for gov bids. It was. Specsmanship. > I am POed that Apple bundled the parity option with the 80SC, so you can't > get a diskless IIfx with parity. I doubt if you need to be. A dealer would probably accomodate you if you really wanted parity with no 80SC. On the other hand, parity buys you little or nothing: from reports so far, a parity error results in little more than a message popping up declaring that the error occurred, and now it's time to reboot. Just detection (boom), no correction. ------------ "...Then anyone who leaves behind him a written manual, and likewise anyone who receives it, in the belief that such writing will be clear and certain, must be exceedingly simple-minded..." Plato, _Phaedrus_
dj02+@andrew.cmu.edu (Dale Allen James) (04/07/90)
"Parity is for Farmers."
kaufman@Neon.Stanford.EDU (Marc T. Kaufman) (04/09/90)
In article <Aa7GgIu00WB9AuHnA8@andrew.cmu.edu> dj02+@andrew.cmu.edu (Dale Allen James) writes: >"Parity is for Farmers." but Farmers buy computers - as Seymour Cray found out... Marc Kaufman (kaufman@Neon.stanford.edu)