James Fraser <[EMAIL PROTECTED]> has raised some intriguing issues: >> Does anyone know what the cutoff point is as far as G3 CPU upgrades >> affecting FBS? >> I know the 800MHz upgrades drop it down from 100MHz to 66.66 and that the >> 500MHz upgrades still allow FBS of 100MHz. Maybe 700MHz is the cutoff point >> for 100MHz bus speeds? [shrugs]
[One response...] > I thought this drop from 100MHz bus speed to 66MHz only affected G4 > upgrades in B&Ws? [JF clarifies....] Sorry, I prolly didn't phrase the question right. What I meant was: the cutoff point for a reduction in FBS when upgrading the CPU in a B&W G3 to either another G3 or a G4 using, say, a Powerlogix or Sonnet (or whatever) ZIF upgrade. -------[I butt in....] The difference appears to be between G3 and G4 ZIFs in relation to the Yosemite mobo architecture. PowerLogix has this to say about it: PowerLogix opted for the IBM PowerPC 750GX for these upgrades, instead of the Motorola G4s, due to a bug we discovered in 2001 (not even Motorola knew about this bug..it even existed in their evaluation boards.) The 745x chip is incompatible with the Motorola bridge chip used on these motherboards. The bug can be worked around, but it requires significant extra circuitry, raising the cost of the product. For these older machines, we did not feel that this extra cost was justified. This extra circuitry creates a performance penalty -- slowing the system bus from 100 MHz to 66 MHz. On the other hand, the PowerLogix G3 ZIF will run at the native G3 bus speed of 100 MHz. http://www.powerlogix.com/products/g3_zif/index.html ------- [JF also wonders....] What prompted this query is that some of the reviews posted at XLR8 make it sound like the "noticeable" difference between, say, a 500MHz upgrade running at a 100MHz bus speed and an 800-900 MHz upgrade running at a 66.66 bus speed may not be all that great. -------[To which I respond....] That lack of "noticeable" difference would most likely be between G4 ZIFs doing "ordinary" *non-AltiVec* tasks. That 33% bus speed drop results in a significant performance hit when running non-AltiVec-aware apps. The folks at PL have a very good point when they say: "Unless you are using Altivec constantly, it is better to have a CPU that runs all tasks faster all the time, than a CPU that runs slower all the time, except for a few Altivec specific tasks." Personally, I'd only use one of the Sonnet Encore ZIFs in a Beige G3 because of its native 66 MHz bus speed. To me, that's an unacceptable trade-off in a B&W. In fact, I'm using a PL 800 MHz ZIF (running @ 900) in my B&W for that very reason. An additional note about different upgrade mfr's: I've always preferred PowerLogix or XLR8 upgrades over Sonnet's. I look for "most bang for the buck" when I try to maximize my Mac. PL and XLR8 just offer more "performance tweaking" options. Sonnet's "Simply Fast" products are for those who like it simple - set it and forget it. ===== Gene, a.k.a. G-Man Friends don't let friends do Windows _______________________________ Do you Yahoo!? Declare Yourself - Register online to vote today! http://vote.yahoo.com -- G-List is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- We have Apple Refurbished Monitors in stock! | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> G-List list info: <http://lowendmac.com/lists/g-list.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/g-list%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
