Should I upgrade my Sawtooth G4's CPU for Logic?
May 15, 2006 6:20 PM   Subscribe

Does it make sense to do a CPU upgrade to a Sawtooth G4 for Logic?

I have a Sawtooth G4 (500MHz iirc) that is CPU-bound running Logic Express, which is all I use this machine for. I've read the other threads about upgrading old macs, and there seems to be a split of opinions, but somewhere on the internet, I came across a forum post that said that upgrade CPUs of similar MHz will beat G5s in Logic/PT CPU-bound tasks because of greater L(n) cache. Apparently audio apps are big cache users. Seeing as how 2GHz upgrade CPUs are around $250, do you think it makes sense to give this a go, or do you think its better to save the time and money and get a low-end newer Mac? Currently, the machine can handle recording about six simultaneous audio tracks, but adding a software instrument, plugins, or more than a couple playback tracks gets spotty.
posted by jeb to Computers & Internet (10 answers total) 1 user marked this as a favorite
Upgrade CPUs of similar MHz will beat G5s in Logic/PT CPU-bound tasks because of greater L(n) cache

This doesn't quite make sense. If you're CPU-bound, then by definition you're not relying on external memory access, so memory cache size wouldn't matter (much -- only for code access, really). I think it's more likely that you're really memory-bound instead. That's the most common situation to be in these days, since memory is so much slower than the CPU, and the CPU is mostly sitting there waiting for memory accesses to finish.

A larger L2/L3 cache helps if you're memory-bound, but increased memory bandwidth also helps a great deal too. IIRC, the G5s had much faster bus speeds than the G4s, and I bet that difference would swamp any change in cache size.

But, as always: the only way to be sure is to test your exact situation.
posted by xil at 6:30 PM on May 15, 2006

You're only going to end up bound by something else if you put a faster CPU in it. It's a bad investment.

xil: As I understand it, a program can appear CPU-bound when the CPU is wasting cycles waiting for the cache.
posted by cillit bang at 6:54 PM on May 15, 2006

Calculate the cost of the upgrade, $250, add the price you may get for your current Mac, $250. and compare to a newer used Mac. A 1.25ghz dual miiror G4, currently about $800.00 on ebay,consider the additional "upgrades" included with the newer Mac (bus speed, RAM speed etc.) and you see it isn't worth upgrading the CPU only
posted by Gungho at 7:54 PM on May 15, 2006

Response by poster: xil, partly what cillit bang said but partly also I meant 'cpu-bound-*looking*'. As in, when running audio apps, a lot of times people run out of disk i/o bandwidth, other (firewire or usb) i/o bandwidth, or memory before getting into a situation where the system says, "don't have the cpu to complete the task". So, yes, this would involve the cpu< ->main memory bus performance, but when I say CPU-bound in this context, I mean 'cache misses->have to go to main memory->CPU idles->processing gets behind->Logic craps out' counts.

On the testing question, I'm kind of thinking if I buy the CPU board used, test it, and find it lacking, I can sell it without losing any money beyond shipping, but I figured I'd ask in case anyone had already tested a situation to save the time.
posted by jeb at 7:59 PM on May 15, 2006

How fragmented is your hard drive?
How many simultaneous tracks do you want to be able to record?
How much memory is on the machine?
Perhaps more memory and a 10,000 rpm drive for recording will help. In other words, you're sure it's the CPU that's the bottleneck here? I used to record multiple tracks on a machine of even less power than yours.
posted by omnidrew at 9:18 PM on May 15, 2006

Also try increasing the latency of the audio system...if Logic express has a separate monitor bus (sorry not familiar with Logic Express - I use Digital Performer) you can still overdub yet prevent the dropouts.
posted by omnidrew at 9:39 PM on May 15, 2006

A CPU-only upgrade is a good investment if you're time-poor. By boosting the current system rather than buying a new one you don't have to re-install anything.

I bought a 333MHz AMD-based CPU upgrade for my Pentium 75 back in the day and I must say that for CPU bound stuff I was very happy with it.
posted by krisjohn at 9:56 PM on May 15, 2006

Response by poster: Harddrive was just reformatted and everything was re-installed, so probably not too fragmented.

I want to be able to record six but be overdubbing onto a software instrument track or two.

1GB memory

Everything points to the CPU. The Logic "system performance" meters show very little disk utilization, I can record six tracks and run into problems much quicker adding plugins and software instruments, etc.

The latency thing I'm having a hard time with. First of all, the system already has pretty high (and variable, due to automatic plugin delay compensation I think) latency. I don't understand how you are supposed to do overdubs on a system like this. That's another reason I want to upgrade the CPU. I figured it would help reduce buffers and consequently latency.
posted by jeb at 6:45 AM on May 16, 2006

Re: Latency

Are you using an external audio interface, or built-in audio?

If you're trying to do overdubs while monitoring the audio input via the interface and the computer, then you're always going to get a bit of latency. To monitor without latency in this instance, you either need an audio interface with direct monitoring or some way of monitoring the signal live - by using an external mixer, say.
posted by coach_mcguirk at 2:12 PM on May 16, 2006

Response by poster: external audio interface (m-audio usb audiosport quattro). it's the overdubbing that's a problem.
posted by jeb at 3:07 PM on May 16, 2006

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