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MacBandit
Sep 16, 2003, 12:02 PM
Does anyone know yet what processor is inside the new line of PowerBooks? I noticed that none of them have an L3 cache could this be a sign of the new Moto processors with full DDR FSB?

ftaok
Sep 16, 2003, 12:09 PM
The 512kB of L2 suggests that these chips are 7457s or 7447s.

I speculated earlier that these chips do have L3 cache, but Apple is choosing not to mention it. I based this on something I read earlier that said that they had 1MB of L3 cache.

Since then, more and more people have been saying that it was a typo. So until someone verifies it, I'm saying they are 7457s.

MacBandit
Sep 16, 2003, 12:21 PM
I agree I'm pretty confident at this point that they are indeed 7457's. Read this article.

http://e-www.motorola.com/webapp/sps/site/prod_summary.jsp?code=MPC7457

I don't know about L3 though. I'm thinking they don't have it for the same reason the G5s don't. It's not really necessary when the FSB is as fast as the system bus or the system memory.

andyjamesnelson
Sep 16, 2003, 12:33 PM
sorry but does this mean that if the chips are a new kind we will see better performance from them and hopefully coolong running temps??

bousozoku
Sep 16, 2003, 12:36 PM
Support for L3 cache, support for error checking cache memory. :) 36-bit memory addressing for 64 GB. :)

They never mention the speed of access to L2 cache. I doubt it's 1:1 as with IBM's G3s. Is it 1:2? This would be especially important, if there is no L3 cache.

MacBandit
Sep 16, 2003, 12:40 PM
Originally posted by andyjamesnelson
sorry but does this mean that if the chips are a new kind we will see better performance from them and hopefully coolong running temps??

Well maybe. If Apple uses a DDR system controller then yes it will make a difference. Other wise it doesn't matter that the 7457 has a faster FSB it will still be slowed down my the system controller. As for cooler I don't know but I would hope so. Also a 512KB L2 cache could easily make as much or more speed difference then having a 1MB or 2MB L3 cache. This is because the L2 cache is built into the chip and accessed at the same speed as the chip. Also because it's in the chip the information has to travel a very short distance greatly reducing latency. L3 cache is typically accessed at a rate of no more then 1/2 of CPU speed. Also it is on the CPU card rather then the on the chip so therefore there is a higher latency in access time.

MacBandit
Sep 16, 2003, 01:13 PM
Originally posted by bousozoku
Support for L3 cache, support for error checking cache memory. :) 36-bit memory addressing for 64 GB. :)

They never mention the speed of access to L2 cache. I doubt it's 1:1 as with IBM's G3s. Is it 1:2? This would be especially important, if there is no L3 cache.

Well I highly doubt it is 1:2 because the L3 on the 7455 use to be 1:2 unless they have backed off on that too.

macrumors12345
Sep 16, 2003, 01:20 PM
Originally posted by bousozoku
Support for L3 cache, support for error checking cache memory. :) 36-bit memory addressing for 64 GB. :)

They never mention the speed of access to L2 cache. I doubt it's 1:1 as with IBM's G3s. Is it 1:2? This would be especially important, if there is no L3 cache.


There is support for L3 cache, but it doesn't seem like Apple chose to use any. I guess they figure that the larger L2 cache is now sufficient...plus the L3 is getting kind of slow relative to the clock speed anyway, so may have limited benefits regardless.

The 512k L2 cache is on chip, so it is 1:1, just like on all modern chips.

And it is necessarily a 7457 (because of the 512k L2). The 7455 only has 256k L2, as you know (and that is not something Apple could change).

bousozoku
Sep 16, 2003, 09:18 PM
Well, prior to the G4, I'd never seen a processor on any size system with an L3 cache. I'd seen the PowerPC_AS processor with 8 MB of L2 cache, which was somewhat impressive, but no L3.

I'd just like to see those iMacs and PowerBooks with 64GB of RAM. :D

MacBandit
Sep 17, 2003, 01:13 AM
As pointed out on another thread the CPU is a 7447. Which really doesn't make a difference. After doing a minor amount of research I found that the 7457 and 7447 are identical in every way except for there footprint size and there pin count. The 7457 is a cheaper (read larger) version of the 7447 intended for desktops.

Also the 7447 does not support L3 cache which could explain the smaller footprint. Something else to note is the 7447/7457 draws 10 watts at 1GHz. This is less then half of what the 7455 drew. Also from other reports I have read the 7447/7457 series of processors could perform as much as 20% better per clock cycle over the 7455.

This kind of explains why Apple went with it even though they lost the L3 cache. It consumes half the power and is faster. Also the FSB is able to scale to 200MHz. All in all this is a fine chip that Apple is using. It's not a G5 but it will definitely satisfy the majority of people for the short term once they learn it's benefits.

panphage
Sep 17, 2003, 01:47 AM
My crusade continues: No DDR support of any kind in any G4 chip. Not even the 74*7s.

MacBandit
Sep 17, 2003, 02:07 AM
Originally posted by panphage
My crusade continues: No DDR support of any kind in any G4 chip. Not even the 74*7s.

Nope at this point the chip that Motorola plans on having RapidIO doesn't have a name based on the PDFs that I have been reading they just call it the G4+. I would assume this is the remnants of the failed G5 development.