Date: Sun, 19 Mar 1995 00:12:57 -0800 (PST) From: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com> To: bde@zeta.org.au (Bruce Evans) Cc: nate@sneezy.sri.com, phk@ref.tfs.com, core@FreeBSD.org, hackers@FreeBSD.org Subject: Re: NMI Error success story Message-ID: <199503190812.AAA22889@gndrsh.aac.dev.com> In-Reply-To: <199503190728.RAA10360@godzilla.zeta.org.au> from "Bruce Evans" at Mar 19, 95 05:28:31 pm
next in thread | previous in thread | raw e-mail | index | archive | help
> > >> But, I did notice that the static cache rams on the new motherboard were > >> 15ns, and on my old (buggy) motherboard they were 25ns. Because I had > >> nothing to lose and feeling like I couldn't make the problem any worse I > >> swapped the cache chips on the motherboards. > > >I will add that I did the same surgery on my machine, which worked fine > >before and after, with the lefthand spin to it that it ran around 10% faster > >afterwards because I could get the cache burst down to 3-1-1-1 instead of > >3-2-2-2. > > Rod tells me it shouldn't work, but I've had good results from setting > the cache burst to 2-1-1-1 on systems with mediocrely rated cache RAMS > (only 20ns for the tag RAM if I remember right). Depends on clock frequency, and based on 33 Mhz: 1/33Mhz = 30nS, yes it should work, just barely with 20nS tag RAM if the total board delay, setup time, and hold times are <10nS. This also means you must be able to do the tag compare in <30nS, which is often the gating issue on witch of 3-x-x-x or 2-x-x-x it is. I didn't say it should'nt work, I said it was on the hairy ass edge of timing. You would probably find that it failed if you cut your power supply to 4.75V (spec margin) and raised the ambient temp to say about 50 degress C. -- Rod Grimes rgrimes@gndrsh.aac.dev.com Accurate Automation Company Custom computers for FreeBSD
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199503190812.AAA22889>