Mersenne Digest Tuesday, April 17 2001 Volume 01 : Number 840 ---------------------------------------------------------------------- Date: Sun, 15 Apr 2001 14:12:22 +0200 From: Alexander Kruppa <[EMAIL PROTECTED]> Subject: Mersenne: A factor of the 31st Fermat number 46931635677864055013377 divides 2^(2^31)+1 On Thursday, 12. April 2001, a factor of the 31st Fermat number (F_31) was discovered, thus proving that F_31 is composite. Since the primality proof by Crandall, Mayer & Papadopoulos, which showed F_24 to be composite, F_31 was the smallest Fermat number whose primality status was unknown. That distinction now goes to F_33; a detailed list of known factors and primality status of Fermat numbers can be found at http://www.prothsearch.net/fermat. The factor was found by Alexander Kruppa on one of five AMD Thunderbird 1GHz computers located at the Technische Universitaet Muenchen. The program that was used is MFAC, written by Tony Forbes. To find a divisor of F_m, MFAC computes a list of numbers of the form (Q*k + h)*2^m + 1, where Q is 4*(2*3*5*..*q) and q is a small prime. In our case, q=11 was used. MFAC chooses h so that gcd(h*2^e + 1, Q) = 1. Composite numbers are eliminated from the list by sieving all multiples of small primes, in our case all primes <= 611999. Each remaining candidate factor d is then tested by verifying the condition 2^2^n == -1 (mod d), for n <= m + x, where x is the greatest integer so that 2^(x+2) | (Q*k + h). It took about 2 weeks to find the factor on the five available machines. The discoverer had checked the range up to k=10^9*2310, where k*2^33+1 is the candidate divisor, on different hardware before (as have other searchers before him) and then assigned subintervals of size 2*10^8*2310 to each machine in turn. At k=5463561471303, the factor was found. At that point, about 2.3*10^11 trial divisions with candidate divisors had been performed, while about 9*10^11 candidate divisors had been eliminated by sieving. The cofactor has 646456971 decimal digits, its primality status is unknown. We would like to thank the staff of Lehrstuhl XIII, Systemarchitektur und Betriebssysteme, an der Technischen Universitaet Muenchen, in particular Christian Rehn, for granting use of their computer hardware. Alexander Kruppa would like to dedicate the discovery to his father, Andreas Kruppa, who passed away while Alexander was making a first contact to Fermat number research by helping with the computation for the F_24 compositeness proof. Alexander Kruppa [EMAIL PROTECTED] Tony Forbes [EMAIL PROTECTED] _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 16 Apr 2001 17:03:14 +0800 From: "Dave Mullen" <[EMAIL PROTECTED]> Subject: Mersenne: O.T. ? Factoring N with MPQS This is a multi-part message in MIME format. - ------=_NextPart_000_0026_01C0C697.203242A0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I've been playing around with MPQS on UBASIC, to see if I could find a = factor of M727 and/or RSA232 ... First I tried the approach of using very large factor bases ... i.e. I'd = sieve to 131071 using UBASIC's PRMDIV function, then check the remaining = residues up to about 2^48 using P-1 ... after testing 2^32 numbers, I = had a couple of full-relations, useless combinations ... When dealing with numbers of this magnitude, that kind of sieving needs = to be done on distributed-computing platforms, with hundreds of machines = taking little sections to sieve and reporting back to a main server ... = like PrimeNet etc. So then I tried a different approach of using a much smaller factor = base, and looking only for partials / double partials ... For the formula F(x) =3D a2x2 + 2abx + c, where b2 - N =3D a2c, and = checking over the range x =3D 0 to x =3D 2^32-1 ... First I look for F(n) where it is the product of small primes x one = large prime P (proved by pseudo-primality testing on a few bases), For each P, I find the two roots n1,n2 =3D=3D 0 mod P for F(x), For n1,n2, then n1+P, n2+P, n1+2P, n2+2P, n1+3P etc I checked F(m) where = it is product of small primes x P x one other large prime Q (again = proved by pseudo-primality testing), Then I scan through the resulting list looking for two results with = different n and P, and the same Q ... =20 So I end up with some Partial Relations thus f ---> some small primes x P1 g ---> some small primes x P2 h ---> some small primes x P1 x Q j ---> some small primes x P2 x Q And a bit of work ... Uf =3D a2f + b, Vf =3D a2 x some small primes x P1 Ug =3D a2g + b, Vg =3D a2 x some small primes x P2 Uh =3D a2h + b, Vh =3D a2 x some small primes x P1 x Q Uj =3D a2j + b, Vj =3D a2 x some small primes x P2 x Q Then, multiplying the relations together ... Uf.Uf.Ug.Ug.Uh.Uh.Uj.Uj =3D=3D a2.a2.a2.a2.lots of small primes = multiplied together.P1.P2.P1.P2.Q.Q (mod N) If the 'lots of small primes multiplied together' is square, I end up = with a Complete Relation of the form X2 =3D=3D Y2 (mod N) Unfortunately, after checking about 1000 Complete Relations derived with = the above system, they all have one common problem ... X =3D=3D Y (mod N) ... so (X-Y) is always a multiple of N ... and = GCD(X-Y,N) =3D 1 ...Damn !!! What am I missing here ... I understood that with MPQS, each complete = relation had a 50:50 chance of yielding a factor of N ? On much smaller N's, i.e. 2^64 or below, the 50:50 yield looks correct, = but when I try on larger N's i.e. M727 or RSA-232, I'm not getting = anything ... I suspect my process of "manufacturing relations" is flawed, can anyone = advise what I'm doing wrong ? Dave - ------=_NextPart_000_0026_01C0C697.203242A0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content=3D"text/html; charset=3Diso-8859-1" = http-equiv=3DContent-Type> <META content=3D"MSHTML 5.00.2614.3500" name=3DGENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=3D#ffffff> <DIV><FONT face=3DArial size=3D2>I've been playing around with MPQS on = UBASIC, to=20 see if I could find a factor of M727 and/or RSA232 ...</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>First I tried the approach of using = very large=20 factor bases ... i.e. I'd sieve to 131071 using UBASIC's PRMDIV = function,=20 then check the remaining residues up to about 2^48 using P-1 ... = after=20 testing 2^32 numbers, I had a couple of = full-relations, useless=20 combinations ...</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>When dealing with numbers of this = magnitude, that=20 kind of sieving needs to be done on distributed-computing platforms, = with=20 hundreds of machines taking little sections to sieve and reporting back = to a=20 main server ... like PrimeNet etc.</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>So then I tried a different approach of = using a=20 much smaller factor base, and looking only for partials / double = partials=20 ...</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>For the formula F(x) =3D a2x2 + 2abx + = c, where b2 -=20 N =3D a2c, and checking over the range x =3D 0 to x =3D 2^32-1 = ...</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>First I look for F(n) where it is the = product of=20 small primes x one large prime P (proved by pseudo-primality testing on = a few=20 bases),</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>For each P, I find the two roots n1,n2 = =3D=3D 0 mod P=20 for F(x),</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>For n1,n2, then n1+P, n2+P, n1+2P, = n2+2P, n1+3P etc=20 I checked F(m) where it is product of small primes x P x one other large = prime Q=20 (again proved by pseudo-primality testing),</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>Then I scan through the resulting list = looking for=20 two results with different n and P, and the same Q ...</FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2>So I end up with some Partial Relations = thus</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>f ---> some small primes x = P1</FONT></DIV> <DIV><FONT face=3DArial size=3D2>g ---> some small primes x = P2</FONT></DIV> <DIV><FONT face=3DArial size=3D2>h ---> some small primes x = P1 x=20 Q</FONT></DIV> <DIV><FONT face=3DArial size=3D2>j ---> some small primes x P2 x = Q</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>And a bit of work ...</FONT></DIV> <DIV> </DIV> <DIV><FONT face=3DArial size=3D2>Uf =3D a2f + b, Vf =3D a2 x some small = primes x=20 P1</FONT></DIV> <DIV><FONT face=3DArial size=3D2> <DIV><FONT face=3DArial size=3D2>Ug =3D a2g + b, Vg =3D a2 x some small = primes x P<FONT=20 face=3DArial size=3D2>2</FONT></FONT></DIV> <DIV><FONT face=3DArial size=3D2><FONT face=3DArial size=3D2>Uh =3D a2h = + b, Vh =3D a2 x=20 some small primes x P1 x Q</DIV> <DIV> <DIV><FONT face=3DArial size=3D2>Uj =3D a2j + b, Vj =3D a2 x some small = primes x P2 x=20 Q</FONT></DIV> <DIV> </DIV> <DIV>Then, multiplying the relations together ...</DIV> <DIV> </DIV> <DIV>Uf.Uf.Ug.Ug.Uh.Uh.Uj.Uj =3D=3D a2.a2.a2.a2.lots of small primes = multiplied=20 together.P1.P2.P1.P2.Q.Q (mod N)</DIV> <DIV> </DIV> <DIV>If the 'lots of small primes multiplied together' is square, I = end up=20 with a Complete Relation of the form X2 =3D=3D Y2 (mod N)</DIV> <DIV> </DIV> <DIV>Unfortunately, after checking about 1000 Complete Relations derived = with=20 the above system, they all have one common problem ...</DIV> <DIV> </DIV> <DIV>X =3D=3D Y (mod N) ... so (X-Y) is always a multiple of N ... = and=20 GCD(X-Y,N) =3D 1 ...Damn !!!</DIV> <DIV> </DIV> <DIV>What am I missing here ... I understood that = with MPQS, each=20 complete relation had a 50:50 chance of yielding a factor of N ?</DIV> <DIV> </DIV> <DIV>On much smaller N's, i.e. 2^64 or below, the 50:50 yield looks = correct, but=20 when I try on larger N's i.e. M727 or RSA-232, I'm not getting = anything=20 ...</DIV> <DIV> </DIV> <DIV>I suspect my process of "manufacturing relations" is flawed, can = anyone=20 advise what I'm doing wrong ?</DIV> <DIV> </DIV> <DIV>Dave</DIV> <DIV> </DIV></FONT></DIV></FONT></FONT></DIV> <DIV> </DIV></BODY></HTML> - ------=_NextPart_000_0026_01C0C697.203242A0-- _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 16 Apr 2001 16:08:08 +0200 From: Alexander Kruppa <[EMAIL PROTECTED]> Subject: Mersenne: CRT isomorphism? Hello, I have a question whether it is possible to uss the CRT to multiply modulo a prime d. \phi(d) = d-1, choose k so that there are primes p_1 .. p_n where (p_1 - -1)*..*(p_n-1) = k*(d-1). Now the system of congruences (mod p_i), i=1..n, will have a cardinality that is a multiple of phi(d). Is there a function f(m) = (m_1, ..., m_n) that gives us an isomorphism between the multiplicative group (mod d) and the groups (mod p_i)? Thanks, Ciao, Alex. _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 16 Apr 2001 18:53:33 +0200 From: "Martijn Kruithof" <[EMAIL PROTECTED]> Subject: RE: Mersenne: PrimeNet vulnerable to client misconfiguration? Hello, if that what you describe is the problem the solution is obvious If a client checked out an (set of) exponent(s) and has not returned it yet just re-assign that same (set of) exponent(s). It could also be that some user does this on purpose for instance someone with 5 machines behind a firewall that cannot contact primenet directly, have one machine grabbing the exponents, and distribute the worktodo files by hand to different machines + copy back the prime.spl files to the machine with internet connectivity. Or have a not so good naming scheme for the machines (as in all machines have the same name) Although I must say some hundred assignments would normally do in these cases. > -----Oorspronkelijk bericht----- > Van: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED]]Namens Nathan Russell > Verzonden: woensdag 11 april 2001 5:25 > Aan: [EMAIL PROTECTED] > Onderwerp: Mersenne: PrimeNet vulnerable to client misconfiguration? > > > I just checked the PrimeNet status page out of curiousity, to find > that only two 10M-digit numbers are available. When I looked at the > work completed figures, it became rather obvious that one particular > user is running machines that are severely misconfigured. I don't > think this is deliberate abuse, since the user does have several > machines running a few dozen exponents with nothing apparently wrong > with them. > > However, the sheer number of assignments involved speaks for itself. > > yeager {~} > cat status.txt | grep netconx | wc -l > 2292 > > What I can't help wondering is whether GIMPS should have some > restriction on how many assignments can be checked out by a given > machine per unit time - in this case, the assignments in question are > being run by only two machines, which appear to be repeatedly losing > track of the work assigned to them. One likely possibility is some > sort of automated program that is repeatedly deleting or blanking the > worktodo.ini file. > > Perhaps there should be hard limit, after which the user is given an > error or sent an email telling them of the situation? > > In this case, there are enough exponents involved to take a top-end > system multiple centuries to complete, and there's no reason why that > should happen without someone contacting PrimeNet to make special > arrangments, if for no other reason than to always have work available > for everyone. > > Nathan > _________________________________________________________________________ > Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm > Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers > _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 16 Apr 2001 14:20:48 -0400 From: Nathan Russell <[EMAIL PROTECTED]> Subject: Re: Mersenne: PrimeNet vulnerable to client misconfiguration? On Mon, 16 Apr 2001 18:53:33 +0200, Martijn Kruithof wrote: > >Hello, > >if that what you describe is the problem the solution is obvious >If a client checked out an (set of) exponent(s) and has not returned it yet >just re-assign that same (set of) exponent(s). The problem is that the two machines that were doing that had used nearly every exponent in a particular category on the server. George could start putting work on the server further in advance, but that would mean less flexibility for everyone. >copy back the prime.spl files to the machine with internet >connectivity. I'm fairly sure that the client security doesn't allow doing that; I could be wrong though. >Although I must say some hundred assignments would normally do in these >cases. That was my conclusion as well. However, Brian Beesley pointed out (offlist) that a large Beowulf cluster (for large values of 'large', to be sure) could complete that number of exponents in a reasonable time. My personal opinion is that people who are going to check out that large a number of exponents ought to let PrimeNet and/or George know in advance, but that might discourage them, so I suppose it's debatable... Nathan _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 16 Apr 2001 19:40:41 US/Eastern From: [EMAIL PROTECTED] Subject: Mersenne: Is there any life here? NO Mail lately, just wanted to know if the list is active! - --------------------------------------------- This message was sent using GSWeb Mail Services. http://www.gasou.edu/gsumail _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 16 Apr 2001 19:40:32 US/Eastern From: [EMAIL PROTECTED] Subject: Mersenne: Is there any life here? NO Mail lately, just wanted to know if the list is active! - --------------------------------------------- This message was sent using GSWeb Mail Services. http://www.gasou.edu/gsumail _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 16 Apr 2001 20:11:10 -0400 (EDT) From: Chip Lynch <[EMAIL PROTECTED]> Subject: Re: Mersenne: Is there any life here? Wow, are you kidding? I thought we'd had a pretty active last couple of weeks. A decent thread on security, and a few math questions. Of course, I could be getting my lists crossed again. :-( - ---Chip On Mon, 16 Apr 2001 [EMAIL PROTECTED] wrote: > NO Mail lately, just wanted to know if the list is > active! > > --------------------------------------------- > This message was sent using GSWeb Mail Services. > http://www.gasou.edu/gsumail > > > _________________________________________________________________________ > Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm > Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers > \\ ^ // (o o) ---oOO--(_)--OOo------------------------------------ | Chip Lynch | Computer Guru | | [EMAIL PROTECTED] | | | www.chiplynch.com | (202) 904-8570 (cell) | ---------------------------------------------------- _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 16 Apr 2001 17:25:00 -0700 (PDT) From: Gordon Irlam <[EMAIL PROTECTED]> Subject: Re: Mersenne: Is there any life here? > NO Mail lately, just wanted to know if the list is > active! Yes, but since you only signed up to [EMAIL PROTECTED] in the last hour, it isn't suprizing you haven't seen any yet. The [EMAIL PROTECTED] list which you subscribed to a few days ago, only averages 2-3 (large) messages per week. gordoni (list admin) _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 16 Apr 2001 17:25:07 -0700 From: "John R Pierce" <[EMAIL PROTECTED]> Subject: Re: Mersenne: Is there any life here? > NO Mail lately, just wanted to know if the list is > active! there's been a few postings a day on the average, about 20 total in the last week. I suspect your sub-scription somehow got un-sub-scripted :) - -jrp _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Mon, 16 Apr 2001 21:04:55 -0400 From: Nathan Russell <[EMAIL PROTECTED]> Subject: Re: Mersenne: Is there any life here? On Mon, 16 Apr 2001 19:40:41 US/Eastern, [EMAIL PROTECTED] wrote: >NO Mail lately, just wanted to know if the list is >active! We're here, all right! Nathan _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Tue, 17 Apr 2001 06:41:54 -0000 From: "Brian J. Beesley" <[EMAIL PROTECTED]> Subject: Mersenne: Re: build-it-yourself Athlon On 16 Apr 2001, at 16:27, Ernst Mayer wrote: > Fry's (a big local discount computer & electronics chain) has a great > deal on build-it-yourself Athlons (US$ 350 for 1.2GHz CPU, MB, case, > floppy, ethernet card, 56K modem & video card) so I'm going to take > the plunge. Does sound like a good bargain... Are you _sure_ this includes the processor? Tip, buy the best heat sink you can find, even if you have to throw away the one supplied. And install an extra case fan. BTW there are now two variants of Athlon (Thunderbird) processor, with 200 MHz (100 MHz DDR) or 266 MHz (133 MHz DDR) front-speed bus. Since the multiplier is fixed, you want to make sure you have the correct type for your motherboard. Some motherboards are switchable for FSB, but, if you install a 266 MHz FSB CPU in a M/B running at 200 MHz FSB, the system will run at only 3/4 of its rated speed. Which will slow it down to about the same speed as a PIII running at the same rated speed. The key is the last character of the part type stamped onto the die. A 200 MHz FSB CPU ends with B whilst a 266 MHz FSB CPU ends with C. Unfortunately you won't easily be able to read this if you have bought a system with the heat sink already stuck onto the processor. > The one question that remains is whether to buy ECC or > non-ECC memory? Neither is terribly expensive (256MB of > Athlon-compatible PC133 memory goes for $45 non-ECC, $90 ECC at > pricewatch.com), but I don't want to pay extra unless I'm sure it will > give some definite advantage. So the question is: does ECC memory of > this kind actually do active error correction, or merely detection? Actually there are several questions here... Memory described as ECC should actively correct single-bit errors and detect most multi-bit errors. If an uncorrected error is detected, it should raise non-maskable interrupt, which (depending on the OS) will probably cause a kernel panic (or BSOD on a Windows system). If an error is detected and corrected, the memory should raise a different interrupt, which the OS may ignore, or log somewhere. My understanding is that the correction is actually done in the DIMM itself, but depends on the appropriate signals being supplied by the chipset. The only experience I have of a corrected memory error on a PC-type system was on a 486 running linux kernel 2.2.x (using old FPM SIMMS); the error was logged in /var/log/messages & the system sailed happily on for months afterwards. Something similar should happen if you have the CPU cache ECC enabled. However, whether this works or not depends on the chipset as well as the BIOS settings and the OS. Note that the VIA chipsets often supplied on Athlon motherboards do NOT support ECC; if you install ECC memory, it functions as non-parity memory. I much prefer ECC memory, but there is absolutely _no_ point in paying extra for ECC memory if the capability is non-functional due to deficiencies in the chipset. However it is definitely worth paying the small amount extra for faster memory (PC133 instead of PC100, even if the memory bus is running at 100 MHz, or CL2 instead of CL3) since this can and usually does significantly benefit system performance - though some tuning of chipset memory timings through BIOS may be necessary. > If OTOH > one only gains the ability to *detect* errors, is Mprime configured > with this in mind, i.e. will it restart from the last savefile if a > memory error is detected? Not relevant - mprime will not be aware of a corrected memory error, whilst a kernel panic will crash the system, so mprime have to restart from the last savefile (once you've stood the system up again!) Even if the system crashes whilst mprime is writing a savefile you should be OK, since the savefile is renamed to something mprime will look for only after the file has been written successfully. Even with full ECC capability, there _could_ still be an uncorrected, undetected error - but this would have to be multi-bit, and therefore rather rare. The chance of this happening without there being a high rate of corrected errors must be rather small. BTW if you're looking for a x86 linux distribution, I'd strongly suggest you look at "Rawhide" which is the beta for RedHat 7.1. This comes with an apparently functional & reasonably stable kernel (v2.4.2 last time I looked); there are _major_ advantages in running a v2.4 kernel on an x86 system (support for UDMA66 & UDMA100 disks, built-in I2C support which is useful for CPU temperature sensing, etc.). But the real point is that it's a lot easier to install Rawhide from scratch than it is to do an install of RH 7.0 then upgrade the kernel. I have little experience of distributions other than RedHat, but I have little doubt that the same principles apply. Regards Brian Beesley _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Tue, 17 Apr 2001 00:58:20 -0700 From: "John R Pierce" <[EMAIL PROTECTED]> Subject: Re: Mersenne: Re: build-it-yourself Athlon > > Fry's (a big local discount computer & electronics chain) has a great > > deal on build-it-yourself Athlons (US$ 350 for 1.2GHz CPU, MB, case, > > floppy, ethernet card, 56K modem & video card) so I'm going to take > > the plunge. those motherboards in those starter kits tend to be JUNK. ... > > The one question that remains is whether to buy ECC or > > non-ECC memory? Neither is terribly expensive (256MB of > > Athlon-compatible PC133 memory goes for $45 non-ECC, $90 ECC at > > pricewatch.com), but I don't want to pay extra unless I'm sure it will > > give some definite advantage. So the question is: does ECC memory of > > this kind actually do active error correction, or merely detection? Does the mobo even support ECC? Its a function of the chipset *and* the system BIOS. I'm not aware of any VIA type motherboards having any sort of parity or ECC capability. > Actually there are several questions here... > > Memory described as ECC should actively correct single-bit errors and > detect most multi-bit errors. If an uncorrected error is detected, it > should raise non-maskable interrupt, which (depending on the OS) will > probably cause a kernel panic (or BSOD on a Windows system). > If an error is detected and corrected, the memory should raise a > different interrupt, which the OS may ignore, or log somewhere. The standard for Hamming code based ECC is correct single bit, and detect double bit errors. more than 2 bits wrong will probably have a ~50% chance of being caught, or possibly mask as a different single bit error and get incorrectly corrected. An uncorrectable error will be treated as a parity error, and either hard halt the box, or cause an abrupt reboot. > My understanding is that the correction is actually done in the DIMM > itself, but depends on the appropriate signals being supplied by the > chipset. No, the correction is done in the chipset. the ram is simply 72 bits instead of 64 bits wide enabling ECC generally adds a clock penalty to every write too, so it slows things down considerably. _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ Date: Tue, 17 Apr 2001 15:32:00 -0500 From: "David L. Nicol" <[EMAIL PROTECTED]> Subject: Mersenne: [Fwd: Plug into peer-to-peer philanthropy with Intel] "A linux version is under development" they claim. Why don't they just recompile it with entropia hooks? - ---------- edited --------------- Intel® Home Computing Newsletter Delivering Intel technology to your inbox April 2001 Revolutionary technology, a new Web resource, and a great deal from Shop Intel(SM)! Find out in this issue how Intel is developing innovative ways for you to use your computer and the Web. - -- Plug into 50 Teraflops of computing power to help find a cure ********************************************************************* Plug into 50 Teraflops of computing power to help find a cure ********************************************************************* Sign up today for the Intel® Philanthropic Peer-to-Peer Program that harnesses the power of your PC to help scientific researchers discover cures for major diseases. Using a peer-to-peer computing model, the program utilizes the Internet to turn the unused computing power of millions of individual PCs into one of the largest computing resources in history. With a goal of registering 6 million people, the program would produce the equivalent of 50 Teraflops of super computing power, with 1 Teraflop equating to 1 trillion floating point operations per second. There's no cost, no catch, and no noticeable impact on your computer's performance, because the program only takes advantage of the processing power you're not using at the time. Make scientific history by downloading the program at intel.com/cure. Or find out more about the program now. *Legal Information and Privacy Policy © 2001 Intel Corporation _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers ------------------------------ End of Mersenne Digest V1 #840 ******************************
