Apple Logic Pro /LogicExpress Discussion

> I'm no expert but I am not so sure about this. What if one 
> CPU grabs some data from RAM then processes it on the next 
> clock cycle while the 2nd CPU accesses the RAM?

That's not at the same time though, is it? It's just close to the same time.

> I don't know 
> how Logic implements dual processors now - but before it used 
> to be that one CPU handled the MIDI and the user interface 
> and graphics and the other did Audio I think. So one 
> processor might be talking to the graphics buss while the 
> other is ram processing.

I have no idea of how this would be split up in Logic.

> In the case of a photoshop filter, if the task is divided 
> half for each processor, it can be pretty close to twice as 
> fast. That "parallel processing" - which we will be seeing 
> more and more. In fact one of the Apple rumor sites says that 
> there is a dual core G4 coming out soon. 

The Apple website shows the single CPU 1.8 being 20% faster than baseline
and the Dual CPU being 66% faster than baseline. That isn't even close to
doubling the speed over the single CPU version and it never will be. And you
have to take into account that the dual CPU model has a faster front side
bus [900 compared to 600] so how much of that speed increase is due to the
increased bus speed?

The data is coming from one hard drive, that hard drive is connected to a
single PCI bus (correct me if I'm wrong) that can only be accessed by one
CPU or the other. Even if both CPUs could access it at the same time, it
could only respond to one at a time (unless they were both requesting the
exact same data). The same is true of Ethernet, Audio cards, video cards and
so on. Getting the data is a big bottle neck. Hard drives are performance
dogs compared to RAM. Then you have the video display. Again, there is only
one bus connected to that card.

The only time you can possibly get close to a true doubling of speed is when
both the code and the data are small enough to fit into the CPU's memory
cache. (As far as I know.)

> That is not clear. The imac is single processor isn't it? 
> Isn't the bus speed slower? No digital audio in/out.

The CPU speed and bus speed of the 20" iMac is the same as the single CPU
1.8 PowerMac. The iMac has digital out, but only analog in. The PowerMac has
Dolby 5.1 digital out and I *think* the iMac is only stereo. That makes it
fairly easy to compare the iMac's CPU performance to the PowerMacs.

> No powercore, no scsi, no graphics board upgrade, the lack of 
> upgradability means you need to replace it sooner. Apple 
> usually hobbles these in various ways.

Yes, to all of the above. That's were I have to decide if it is worth an
extra $1000 to get the PowerMac because it costs $999 to get that 20"
display. If I put that $999 in the money market, I might have enough money
to buy another Mac in a couple of years or I could spend it on a really nice
I/O device. Right now all I have is a TASCAM US-122. Which has only two
inputs and two outputs.

> The joy of being a modern musician. I got some of those hooks 
> you hang over the door to hang shirts, and use them to hold 
> cables without being tightly coiled. I also went to the 
> hardware store got some of those plastic ties to bundle cables.

LOL! I don't have the hooks, but I have the plastic ties. ;)

Kamm