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memory overclocking

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locust

Registered
Joined
Jan 3, 2001
Can someone more educated than me explain what the theoretical max sustained bandwidth is on a standard pc 133 stick of mem? I understand that DDR 2100 means 2.1 gb/sec, but how much can we expect to get at most from a pc 133 stick?

I ask this because my 1.28 gz tbird must, it seems to be, be pushing the saturation limit, at around 610/690 on sandra on the kt7. Not the a, mind you, but the stock 133.

thx,
/l
 

Vector

Member
Joined
Dec 26, 2000
Location
Baton Rouge, LA
Standard PC133 RAM will tach out somewhere around 1GB/s max memory bandwith...actually like 1024GB, but who's counting...

I'm thinking that somewhere around 1.2GHz or so, the memory bottleneck begins to catch up with the system; thus the system is slowed by internal data transfer...

To counter this, you can (and you obviously have, since you're running at 1.28GHz) increase the fsb and overclock the memory...but whatever you do, don't lower the memory timings--try to get the memory to the highest frequency it will go at cas2 without running into system instability...memory will let you know that it is unstable right away

hope that helped
 
OP
L

locust

Registered
Joined
Jan 3, 2001
Yeah, that sounds about right. The issue here is that the memory is fucking pinned @ host plus pci, which means currently it's running at 148 mhz with no problem. I can't say enough about this mushkin sdram (the pc133 2-2-2). Cas 2, 4-way-interleaving, set to hi, everything turbo.

I'm still not sure, tho, what is causing the instability above 115 mhz fsb, whether it's cooling of the cpu (just a straight retail fan with arctic silver applied) or the mem. In any case, my original question -

so there's 1 gb of thru put with regular pc133. If I'm getting numbers like these sandra numbers and linpack tests and flops, which seem to indicate that I'm not going over the bw max (let's say 700 mb a sec), is that the case, or am i comparing apples and oranges.

I'm curious because in games like sacrifice I STILL notice slowdown with insane details turned on, etc and it does seem to me to be a limitation of my mem and graphics bw (card is an ultra)

/l
 

Rob Cork

Senior Member
Joined
Dec 17, 2000
Location
Woodcote, UK
It's not your memory/cooling/cpu that's causing instability above 115MHz fsb - it's the KT133 chipset on the KT7. 115 is very high for a KT133, most won't go above 110MHz, it seems they were intentionally crippled by VIA to limit high fsb speeds. The new KT133a chipset that you may have heard a lot about is great because it is exactly the same wonderful chipset, but with ATA100 support and true 133MHz fsb - allowing greater bandwith between the cpu and northbridge.

If you want to try and get more from the cpu you will need to unlock the mutliplier with the 'pencil trick' - there's guides at http://www.tomshardware.com/cpu/00q3/000711/index.html and http://www.athlonoc.com/unlocking.htm . I'm not sure how much more you'll get from that chip, but it's gotta be a worth a try for 1300 :)

Oh yeah, don't take offense please, but if you're going to use strong language, use the * key instead, that's what it's there for ;-) A lot of people try hard to keep these forums clean, please respect their efforts.