Necessay RAM for factoring

[jasong]

I don't have enough money to make a difference if I were to move out, but I so seldom get a chance to make a major purchase I savor it when I save up.

1.75GHz Sempron and I would like enough RAM to factor numbers in the second step at least until they get to n=15 million.

DDR-SDRAM
Frequency 166.5MHz
2.5-3-2-7 latencies
(512MB at the moment)

advice welcome, including future-proofing advice)

[hhh]

I remember George (prime95) pointed out somewhen that there is a big speed diference between 100 MB allocated and 200MB allocated, but not such a big one between 200 and 400 MB (or 400 and 800). In other words: more mem is better, but the speed increase is not even linear.
So I guess you can save the money and buy something else, an for example, as IMHO it's quite OK is you give say 350MB to prime95.
If you want absolutely increase your throughput with that money, you may buy another old machine with few mem and let it run only stage1, transferring the save files to your more recent machine. But...
Other opinions?
Yours H.

[vjs]

hhh is correct, prime95 and ecm6.0 etc will simply split the stage2 into pieces if you don't have enough memory.

I'd probably stick with 512mb for that machine, although it was fast in it's day your probably better off saving up for a complete board a processor upgrade.

[jasong]

I think I'm confused, I thought Prime95 did EVERYTHING!

Did I misunderstand about running stage 2?

[Hades_au]

Prime95 does do everything with P1 testing.

I'm not sure what the question is though. What did you do to get it to run Stage 1 only? By default, it will run both.

512mb of ram is enough to run both stages of P1 tests at the default settings. Most of my boxes only have 512 in them and they run up to 60000, 630000 with 200mb of ram allocated.

Have you changed the default setting of available ram ?? I think (from what I remember) the default setting is 8mb, or it used to be anyway.

How did you set it up? From the instructions here http://www.geocities.com/omboohankvald/Factp95.html


The Sempron isn't the fastest cpu for P1 factoring, but it will work. I'd say, save your money, decide on what project you want to do, then go from there. Unfortunately, no 1 processor will be great at everything, the decision on what to buy usually comes down to personal preferences.

[jasong]

Originally posted by Hades_au
Prime95 does do everything with P1 testing.

I'm not sure what the question is though. What did you do to get it to run Stage 1 only? By default, it will run both.

Maybe I'm simply confused and actually ran both, I don't know. It just seems like the output looks slightly different from when I ran this same setup some months back. Shouldn't there be a line that says "Running stage 2 GCD" or some such thing? It doesn't seem to be printing a stage 2 line, that's what's confusing me.

If I screwed up somewhere and set it up wrong, I don't know how.

[vjs]

What does your worktodo.ini look like??

[jasong]

Originally posted by vjs
What does your worktodo.ini look like??

I've deleted it since then but I think the line to create it was:

makewtd 10500000 10501000 49.5 1.7

Does that look right?

[vjs]

That looks correct!!

So you were probably just fine.

Your worktodo.ini would have contain lines that looked like this...

Pfactor=k,2,n,1,49.5,1.7 (where k and n are values of the test obviously)

Your other alternative is to create the worktodo in the same fashion as you did except change the lines slightly...

Pminus1=k,2,n,B1,B2

Where you specify particular B1 and B2 values, since your short on memory you could run a slightly larger B1 and a smaller B2 if you wish.
----------------------

here is a step by step of what I did to create a custom worktodo.ini

Start off using Mikes program but use ridiculous numbers...

makewtd 10500000 10501000 46 3

lines are created

Pfactor=k,2,n,1,46,3

Now open the worktodo in your favorite text editor.

Replace Pfactor= with Pminus1=

Replace ,1,46,3 with ,1,b1,b2

Values of B1=40000 to 60000 work pretty well, I believe Hades_Au is using 60000+

Then use a b2 somewhere around 8 to 14 times B1, b2=b1x10 use to be pretty standard but stage2 is now much faster than stage1 "If you have the memory".

On my machine a B2=B1x14 pretty much spends equal time in stage 1 and 2. (barton with 2G of memory).

I'd suggest you try values of B1=50000 B2=400000 if you feel your machine memory limited.

so your final line looks something like

Pminus1=k,2,n,50000,400000

--------------------------------------------------

The above is also how one transfers stage1 and stage 2 stest between machines.

If you were to use the following line

Pminus1=k,2,n,50000,50000

Only stage 1 would be done, then you transfer the files to another machine and run...

Pminus1=k,2,n,50000,400000

Prime95 will say something like stage1 complete 1sec starting stage2.

Inaddition if you wanted to re-run some files to higher B2 values...

First run
Pminus1=k,2,n,50000,400000

Then on the same machine run

Pminus1=k,2,n,50000,800000-400000 (or is it ,400000-800000

--------------------------------------

Hope this helps, best thing to do is try a few tests and see what happens. If you make a mistake in the worktodo.ini prime95 generally doesn't start.

You can try a smaller test first...

Pminus1=4847,2,2800791,1,20000,20000 <--- should complete in about 15 minutes for stage1

then

Pminus1=4847,2,2800791,1,20000,200000 <--- should restart the test and run stage2, using stage 1 from before.

Pminus1=4847,2,2800791,1,20000,200000-400000 <--- should run stage2 again out to a higher level.

[dudlio]

future proofing advice...no problem.

I usually start with a $230 processor, which would be the Athlon 64 3700. Get the newest motherboard (Abit AT8, not yet shipping) which should be $150-200. That will allow for a processor upgrade (which you will never do anyway). That also allows the fastest ram, ddr-2. Total system cost is about $600 and will last 5 years. Can't do better unless you blow $700 on a processor alone, and then you're only buying another year.

Most underappreciated upgrades are: A monitor that will outlast the system, and SCSI disks. The first one I can vouch for, the second one just seems like....they wouldn't sell the damn things if they weren't worth it.

[vjs]

I can whole heartily agree on the scsi. I've been putting u320 controller cards and 15K scsi's in all my machines lately. The performance "feel" is alot better. 36G scsi's off ebay are pretty cheap now, and they should outlast any ide.

If you need additional storage buy a large ide, O/S, games, apps, swap file all on scsi, generally doesn't take more than 12G anyways.

[dudlio]

>I can whole heartily agree on the scsi. I've been putting u320 controller cards
>and 15K scsi's in all my machines lately. The performance "feel" is alot better

Nice. Disk subsystem under Windows has been pitiful for years. It takes minutes just to copy a file and the system tends to hang in the process. Meanwhile, efforts at reducing price have reduced most IDE warranties to 1 year. Standard SCSI warranty is 5 years. I have already fixed one client's system where the problem was reasonably the cheap stock hard drive.

[Greenbank]

Hard drives are for wimps.

One of my sieving machine boots from cdrom and installs a few bits in a 16MB ramdisk. It's been happily crunching away like this for 3 months.

[Frodo42]

Originally posted by Greenbank
Hard drives are for wimps.

One of my sieving machine boots from cdrom and installs a few bits in a 16MB ramdisk. It's been happily crunching away like this for 3 months.

That really sounds interesting ... what kind of OS do you boot from the CDROM ... Knoppix?

I might want to consider a setup like this for one of my P4's here as long as I have no need for the big server part I have set up on it.

[Greenbank]

Nope, just a bog standard Redhat 9 (Shrike) Linux CD.

I just boot it with "linux text ramdisk_size=16000"

Once it's booted you have to go through a few of the menus (skip the media check, select the appropriate language and keyboard). When it runs anaconda you can switch to virtual console 2 (ALT+F2) and there's an sh# prompt.

pump; # Gets an IP from DHCP server
mke2fs -m 0 /dev/ram; # Format 16MB ram disk
mkdir /ram; # Make mount point for it
mount /dev/ram /ram; # Mount it

Use scp to copy in SoB.dat, proth_sieve, existing fact*.txt and SoBStatus.dat if needed.
Also scp in my monitor program which forwards the factors and SoBStatus.dat to another machine.
./proth_sieve > /dev/null 2>&1 &

Leave machine alone. Monitor progress with Sobistrator.

Before I had my monitor program which forwards things to another host I used to periodically go on there and run a script to scp the files (fact*.txt and SoBStatus.dat) to another machine.

The monitor program limits the amount of work lost if the machine crashes (or the cleaners at work unplug the machine).

My two sieving boxes would cost me under 150 UKP each with no HDD. Asus Terminator barebones, cheap optical drive, Athlon XP 2200+ chip, 256mb memory. 500kp/sec with the 8k 50M dat file.

[Frodo42]

Originally posted by Greenbank
Nope, just a bog standard Redhat 9 (Shrike) Linux CD.

Thank you for the tips here.
I'll see if I can't set up something similar ... I have often been thinking about building my own knoppix CD's for diffrent purposes. I could have one of them and an usb-key in the side pocket of my bag for when I am out visiting people and just want to borrow their computers (I become every more annoyed when I have to use windows for some reason).

It should be possible to build this so I don't even have to set up a monitor or keyboard to my "little P4-server" here, I just need to get SSHD up and running... that will come in handy when the already worn harddisk that is in there totally fails on me.

I really wish I had more time on my hands for projects like this

[jmblazek]

I'm a novice...just an interested computer user who hates to waste computer cycles...and likes a little math.

I followed the download and install directions. After several days I looked in the fact.txt file and noticed that something didn't look right.

[Mon Feb 20 00:20:17 2006]
21181*2^10860020+1 completed P-1, B1=35000, Wc1: 18FCB560

There was no B2 stage. I played with the Prime95 settings and discovered that if I changed my memory, the program started B2 testing.

I then read this thread and started playing with memory settings. I'm at 120MB and B1=60000 and B2=540000. Is this appropriate?

Also, as I was about 3/4 through the range, should I redo the range with the new settings?