From polowin $#at#$ hyper.hyper.com Thu Apr 27 10:46:07 1995 Received: from www.hyper.com for polowin _-at-_)hyper.hyper.com by www.ccl.net (8.6.10/930601.1506) id KAA17448; Thu, 27 Apr 1995 10:34:15 -0400 Received: from hyper.hyper.com (hyper.hyper.com [204.50.3.217]) by www.hyper.com (8.6.9/8.6.9) with SMTP id KAA09522 for < %-% at %-% www.hyper.com:CHEMISTRY %-% at %-% ccl.net>; Thu, 27 Apr 1995 10:28:02 -0400 Received: by hyper.hyper.com (920330.SGI/920502.SGI) for :~at~:www.hyper.com:CHEMISTRY:~at~:ccl.net id AA03879; Thu, 27 Apr 95 10:46:58 -0400 Date: Thu, 27 Apr 95 10:46:58 -0400 From: polowin -A_T- hyper.hyper.com (Joel Polowin) Message-Id: <9504271446.AA03879 -x- at -x- hyper.hyper.com> To: CHEMISTRY ^%at%^ ccl.net Subject: Re: Nine bits v. Eight > Date: Tue, 25 Apr 1995 17:08:57 -0400 (EDT) > From: Friedman > Subject: CCL:Nine bits v. Eight > > We are purchasing a pentium 100MHZ PC to speed up our runs using Hyperchem > and Gaussian 92W/DFT. I was alerted by several people that many of the newer > PCs use 8 bit SIMMs now. I've gotten differing opinions on whether parity > checking is needed. I would appreciate hearing from anyone with an informed > opinion as to the risks (no pun) involved. Hypercube and Gaussian boffins > especially welcome. I relayed the question to our hardware expert, Edmund Lam. He responded: --------- In the past, PC used 9 bit wide RAM. This architecture was used to ensure detection of RAM errors. In recent times, the quality of RAM and mainboards have curved the need for parity detection. MACs have always run 8 bit wide RAM. Workstations such as the Sparcs also use 8 bit wide RAM. The extra bit can be used to detect a memory error, but is not sufficient to correct it. ---------- My own experience with parity checking was a PC that I ended up lugging back and forth to and from the shop for nearly a year because it kept giving me "Parity error -- system halted" crashes at home but worked fine at the shop. Shop kept claiming it was a problem with the RAM, and replacing the chips. Took them a year to clue in that the problem was actually with the motherboard; after they replaced *that*, the machine gave no more trouble. Whether that little story argues FOR or AGAINST the merits of parity-checking is something I'll leave for others to sort out. :-) Regards, Joel ------------ Joel Polowin, Ph.D. Manager, Scientific Support Email to: polowin ^at^ hyper.com Hypercube Inc, 419 Phillip St, Waterloo, Ont, Canada N2L 3X2 (519)725-4040 Info requests to: info \\at// hyper.com Support questions to: support \\at// hyper.com Email group: Send "subscribe hyperchem" to hyperchem-request \\at// hyper.com WWW: http://www.hyper.com/