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Ditching the G4 series completely, not for iMacs, not for iBooks, not for Nothin!

D

DharvaBinky

macrumors member
Original poster
Jul 18, 2002
89
0
Lafayette, LA
Take a quick look at this:

roadmap_small.jpg


This graphic is from IBM's website regarding the roadmap for their PPC processors. Note that it does not include the G4, but rather, is a road map of their G3 line. It's small and hard to read, but lets examine the features there in the yellow "planned" zone right *after* the currently shipping:

Multicore SuperScalar
SMP Capable
Integrated SIMD Engine
RapidIO
n-way Crossbaring

The "next generation" of G3s after that have some other esoteric names except for:

New High-speed Interface

Ok... So by IBM's own roadmap... their G3 line will soon be more advanced and clocked higher than Motorola's G4. And I mean... what *is* a G4, really, but a G3 with a beefed up Float unit and Altivec strapped on the back (yes yes, it's more than that, but still, is it really?)?

Sooo... What with Apple's current coziness with IBM, I'm thinking this:

Apple wouldn't be able to "downgrade" the iMac to use a chip which is titled a "G3", however, IBM uses a 3 digit numbering scheme. Right now, the G3 is the 750 series. The upcoming ppc970 is going to be our 64-bit proline chip. What comes between 7 and 9?

<drool>

The IBM ppc8xx series? :) These pumped up G3s would be a great addition to the consumer lines. Not only will IBM have them running cheap and small and fast, but they'll have Altivec and RapidIO to make up for the G4s "MaxBus(t)", and subsequent generations would go even faster... sooo...

Does anyone care to comment on the possibility of the usage of a totally ficticious piece of silicon that I"m deriving out of thin air using a gap in an arbitrary numbering scheme and a dated roadmap pic? *grin*

Dharvabinky
 
Where in all this do you get that every step on the diagram are G3s. It looks to me that the later chips are describing the PPC970. Also the title of the document is simply there PPC roadmap. The roadmap doesn't necessarily describe the evolution of one processor type but rather the map on which IBM plans on building there processor market. It could include everything from PPC601s through PPC970+ and everything in between if they chose to.
 
This roadmap is really old - several years. We know the 970 won't have RapidIO or be dual-core, so you're right that this must be referring to the G3. But I think IBM's plans have changed a little since this roadmap was published. A PowerPC 8xx would be a waste of development effort when all Apple/IBM would have to do is throw a lower-clocked 970 into the iMac with no L3 cache. The 970 is a "pro line" chip, but by CPU standards it's very small and low-power. It's the new Celeron of the PowerPC world. As it is, it's a compromise between the large Power4 and the small embedded PPCs. The 970 would even work great in an iBook...

Power Mac 1.6, 1.7, 1.8GHz, more cache
PowerBook 1.3, 1.4GHz, more cache
iMac 1.3, 1.4GHz, less cache
iBook 1.2, 1.3GHz, less cache
 
Ok... So by IBM's own roadmap... their G3 line will soon be more advanced and clocked higher than Motorola's G4. And I mean... what *is* a G4, really, but a G3 with a beefed up Float unit and Altivec strapped on the back (yes yes, it's more than that, but still, is it really?)?

It's a beefed down floating point unit with AltiVec. AltiVec takes most of the space the fp unit would normally have which explains why fp performance has been so poor after the 604e.

There's nothing that says that the orange sections are G3 processors. In fact, where it says multicore should be a clue that it isn't. G3s don't support much of anything multi.

The 8xx or 8xxxx series would be the mythical G5. It just looks as though IBM got tired of waiting for Motorola to get its act together and bypassed it with a single-minded design.
 
Originally posted by MacBandit
Where in all this do you get that every step on the diagram are G3s.
Click to expand...

I would normally agree, however, no where in the list does it refer to the transition to 64-bit computing. Certainly a *huge* architectural change that would deserve a bullet mark, don't you think?

Additionally, RapidIO is *not* on the map for the ppc970.... It could be a reach, but why, after being so mistreated by Motorola, would Apple want to give them any business at all? I understand that IBM could and does fab G4s, however, they don't *develop* them, and it seems like Motorola's commitment to non-embeded is over. Leaving Apple with a consumer line needing chips.

This fits in with the idea of the 970, too, in my opinion. The ppc970 is *not* a G5, since it is just refined 4th generation technology from IBM. It works and runs better than a ppc745x, but it's still just IBM's 4th gen chip (Power4+) reworked. Apple needs to be able to differentiate their Pro line from the Consumer line. A stright ppc970 across the board would not allow them to do this except by speeds, which isn't as charming to consumers who want to feel special for buying "pro". An IBM ppc8xx based on the G3, but with Altivec and a nice bus, would give them a clear distinction. 32-bit IBM PPCs for Maw and Paw, 64-bit IBM PPCs for the pro.

Dharvabinky
 
Yeah it's the multicore part that gave away the Power4 really.

I think initially IBM planned on producing a consumer Power4 with multicore and RapidIO and other new technologies. I think the reason for the change is a push from Apple to have a consumer chip as soon as possible that will be competitive with X86 processors and will also scale quickly.
 
Originally posted by alex_ant
This roadmap is really old - several years. We know the 970 won't have RapidIO or be dual-core, so you're right that this must be referring to the G3. But I think IBM's plans have changed a little since this roadmap was published. A PowerPC 8xx would be a waste of development effort when all Apple/IBM would have to do is throw a lower-clocked 970 into the iMac with no L3 cache. The 970 is a "pro line" chip, but by CPU standards it's very small and low-power. It's the new Celeron of the PowerPC world. As it is, it's a compromise between the large Power4 and the small embedded PPCs. The 970 would even work great in an iBook...
Click to expand...

Ummm, not to be knittpicky, but the 970 doesn't support L3 cache what so ever. It just has a huge L2 cache compared to anything the G4 could have. The only reason the G4 was designed to have L3 cache is that Moto couldn't get the processor to support that much L2 cache.....heck, they finally got it back up to 512kb of L2 for their next gen of G4s. I remember when they had 1MB of it! I think the biggest reason for the L3 cache is that Moto didn't want to increase the size of the processor b/c it is used in tons of imbedded markets, so they just added support for L3 cache to offset the lack of L2 cache.
 
King arthur i think is correct , L3 was making up for again the lack of ability for the g4. I have not seen anything that states a l3 on the 970. it wont be needed as far as i can see. The g4 needed this and more. I think they should use the 970 in the imac and powermacs. After all since you cant upgrade the imac you will buy another event=ually. Just use a lower speed. But to keep the imac constantly on low end sucks! If you need expansion and growth etc buy the powermac, if not give me a 970 imac! Just more of apple screwing themselves. They should ditch the g4 all together in my opinion since it is so behind the p4. How about a nice 1.2 ghz 970 in the imac and a 1.4 and 1.8 ghz in a very expandable powermac? Then give us those build how you want it options for the powermac. Size of drive, super or combo opticle drive, how much memory and what kind of video card you want. Use same architecture in both imac and powermac! If they absolutely have to keep buying g4s then stick em in the Emac but please give me a 970 imac.
 
As much as people would like to see the G4 go out the door, I personally don't see that happening in the near future. Number one, the iMac just got the G4 (yeah it has been over a year, but that is a relatively short time for a processor in a system). Number two: Moto is upgrading the G4 to include some new features (faster processor and more cache, etc). Number three, Apple isn't going to abandon a chip that they have toted for so long as such a great chip. Number four: Apple would never go back to the G3 without calling it something else to make it sound like a different chip (like Intel did with the celeron, which is just a Pentium 2 with no L2 cache).

I forsee the iBook getting the G4, then PowerMac getting the 970, etc. Apple has reached a point of no return in their marketing of the G4, so they are going to have to hope Moto does something decent with the G4 in the upcomming year or so.
 
KingArthur:

You do realize that the backside L2 on older G4's simply became backside L3 when the on-die L2 was added, don't you? As far as I know there were no changes to it, just a name demotion.

It just has a huge L2 cache compared to anything the G4 could have.
Click to expand...
Huh? The 7457 will go to 512k.
 
The 7457 is supposed to go into production this 4 th qtr, this means 2004 before the imac could get one. So will apple wait until 2004 or will they put a new 970 in the imac or or risk heat issues with current g4 and take it to 1.2ghz? Anyone know if the current 1 gig imac chip has a heat sink or a fan on it?
 
Originally posted by KingArthur
Ummm, not to be knittpicky, but the 970 doesn't support L3 cache what so ever. It just has a huge L2 cache compared to anything the G4 could have. The only reason the G4 was designed to have L3 cache is that Moto couldn't get the processor to support that much L2 cache.....heck, they finally got it back up to 512kb of L2 for their next gen of G4s. I remember when they had 1MB of it! I think the biggest reason for the L3 cache is that Moto didn't want to increase the size of the processor b/c it is used in tons of imbedded markets, so they just added support for L3 cache to offset the lack of L2 cache.
Click to expand...
Well, whatever. The point is that it would be easy to reduce the 970's performance such that an 8xx chip wouldn't be necessary.
 
alex_ant:

The point is that it would be easy to reduce the 970's performance such that an 8xx chip wouldn't be necessary.
Click to expand...
But can they reduce the cost enough? Considering the more complex chipset, I don't think that they can.
 
Originally posted by ddtlm
alex_ant:


But can they reduce the cost enough? Considering the more complex chipset, I don't think that they can.
Click to expand...
Good question but if apple said we want millions of these chips and are going to use them everywhere would that make them cheaper. And the 970 is supposed to be a cheaper power4 and with no l3 that should make it very competetive with the g4 7457?
 
Dont Hurt Me:

That slow offdie crap L3 isn't all that exensive I think, but in any case, we're talking about iMacs and stuff right? They'll never get L3s, especially not if the high-end would end up with less total cache.
 
ddtlm:

You know, I never thought of it that way, but yeah, all level 3 cache is, is backside L2 cache. It runs at 1/2 processor speed (backside L2 cache did that), it is just high-speed RAM (same with BS L2 cache). Lol. I mean, it makes sense seeing it that way. Apple got rid of it for a short amount of time....I believe the last system to use BS L2 cache was the first TiBooks. Then they realized what a performance hit they were taking and they added it back in on top of the on-chip L2 cache. And I believe the largest L2 cache size we ever saw was 1MB per cpu....what is the L3 cache size? 1MB per cpu. Looks like Apple pulled a fast one past me;).

Anyway. I bet Apple will try one more speed boost on the current G4 for the iMacs and then wait for the 7457. No matter what, I REALLY don't think that Apple will be putting the 970 in any iMacs or iBooks any time soon. They have to maintain a reasoning behind their high-prices for the PowerMacs and PowerBooks. L3 cache for the iMac? I doubt it. The only reason I could see them doing that is if they only had a really minor speed-bump and needed something to pawn off to the general public as a major improvement. I think it will take up too much space, though. I also doubt it b/c soon we will see the 7457 which will double the cache and make them on par with other processors on the market. I would also expect the iBook to go G4 (7455) a few months before the iMac and PowerBook goes to the 7457. Then after a long while, we will see the PowerBook go 970 as the iBook goes to the 7457 and stays there for quite a while. Once they max out the 7457, if Moto hasn't come out with a faster G4 or something, then the iMac will finally go 970 as hopefully the next big thing from either Moto or IBM comes out (and I would put my money on IBM).

As a last note: G3 iMacs again? Hell no! You realize that the current iBook G3 processors have been out at that speed for years?! The G3 R&D has been abandoned and all that they are doing is using the already developed G3s. As soon as they wean the iBook off of the G3, they will probably do with it what they have done with the G3 iMacs. They will just create a ton of G3s at the current speed they are at and stop producing them all together. They will just slowly feed off of the G3 stock until they are gone and then they will just end the use of the G3 altogether.

Just my three cents worth:D
 
Motorola has its hold on G4 and AltiVec. IBM did not want to go that route. But IBM will be implementing Vector Processing unit similar to AltiVec on 970.

So what are the chances of IBM sneaking in AltiVec like feature onto G3? G3 will most likely go on in iBooks little longer. Could this be part of roadmap for future G3?
 
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