Date: Tue, 28 Oct 1997 18:27:42 -0800 From: David Greenman <dg@root.com> To: Mikael Karpberg <karpen@ocean.campus.luth.se> Cc: hackers@FreeBSD.ORG Subject: Re: Parity Ram Message-ID: <199710290227.SAA20846@implode.root.com> In-Reply-To: Your message of "Wed, 29 Oct 1997 03:29:12 %2B0100." <199710290229.DAA07708@ocean.campus.luth.se>
next in thread | previous in thread | raw e-mail | index | archive | help
>> In order to update the memory, the ECC must be recalculated over the >> entire 64bit quadword. This escentially means that you have to read the >> memory first, apply the changes/calculate the new ECC and then write it >> back. Obviously,this makes memory writes quite a bit slower. > >Hmm... It's still not quite clear to me. That is, does this slow my >computer down, in case I use ECC? Yes. >It seems to me all this could be done on the DIMM/SIMM, or something, >possibly clocked at multiple of the bus clockspeed, and therefor >not effect the rate at which memory could be read/written over the bus >by the CPU. It may seem that way, but it isn't. :-) >If that's not the case, and the computer is actually slowed down by ECC, >how much performace do you loose? 0.1%? 5%? 30%? Probably less than 5%, but it will depend on the application. -DG David Greenman Core-team/Principal Architect, The FreeBSD Project
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199710290227.SAA20846>