> From: Clark Martin <[EMAIL PROTECTED]> > Subject: Re: [PCI] 7500 Questions > > At 10:16 AM +1000 6/17/04, David Elmo wrote: >>> From: Clark Martin <[EMAIL PROTECTED]> >>> Subject: Re: [PCI] 7500 Questions ...
>> In a 7600 I have a Powerlogic G3/4 processor with a 1MB backside, in the >> Cache Profiler software one can alter the cache ratio from 1:1 to 3:1 with >> 3:2. 2:1, and 5:2 in between. One can also set the switches on the cpu for >> different clock speeds. I had 360Mhz at 3:1 (giving a cache speed of 135MHz) >> for a long time and it was very steady indeed. >> >> But one day, a few months ago, I got all wild and upped the clock speed to >> 405MHz, keeping the 3:1 backside ratio. All was fine. Recently, I thought, >> hell, why not up the ratio a notch to 5:2 (going to a backside speed of >> 162MHz - closer to what I run an excellent XLR8 G3 CPU on my 7300). >> >> But I got more freezes which may be attributable to this cache ratio change >> (not sure, there are complications). But now you raise this Clark, one of >> those wild feelings came rushing over me and I have just changed it to 2:1 >> and will know the effects next few times I start. > > Well, anytime you up the clock speed (or any other speed setting) to > higher than it's specified value you are risking buggy operations. > > You may be better off running it at a slower clock speed and a higher > cache ratio (2:1). While you may or may not get a 1:1 cache ratio to > work it would be rather iffy. The whole point of the backside cache > is to provide a cache in between the CPU speed (L1 cache) and the bus > speed (L2 cache). > > A G3 gets most of it's performance boost from the backside cache. > -- > Clark Martin My Powerlogix daughter card has a range of specified values. For example, if the motherboard allows a 50MHz bus speed, it runs at 450MHz. But I go conservative at 405MHz processor speed and 45MHz bus speed (which is within the capability of the 7600 motherboard). There is some nice software to show all the many combinations of Powerlogix processor speed/bus speed, called Switch Demo where you can - via mouse clicks - simulate turning on and off the eight switches that are on the card. Btw, Powerlogix made a bit of a hash of their tables when originally providing info on this, causing confusion and, finally resulting in this Switch Demo among further explanations. You mentioning the desirability of a backside that goes to at least 2:1 caused me to up mine to this and it seems good after two starts (but early days yet). There may be something about 2:1 that is particularly good generally ... I do notice now that this is the figure in illustrations used in Read Me's. David Elmo -- PCI-PowerMacs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Sonnet & PowerLogix Upgrades - start at $169 | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> PCI-PowerMacs list info: <http://lowendmac.com/lists/pci-powermacs.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/pci-powermacs%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
