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Simple G5 memory question
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denim
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Sep 17, 2003, 01:21 PM
 
What is the maximum theoretical DIMM size the G5 machines can take? I know they can take 1GB parts, but when a 4GB or 16GB or 64GB(!) part becomes available, can they use it?
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devmage
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Sep 17, 2003, 01:29 PM
 
That would depend on apple's design. Its probably something that could be changed in the bios to allow for it. Of course we know the G5 should be able to address it.

I've already seen statements that sugest the G5 doesn't support the 2Gig modules because they weren't widely available (Though I see them on pricewatch.com) but that the machine will be able to support them. That increases the G5's configurable ram to 16Gigs

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denim  (op)
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Sep 17, 2003, 01:40 PM
 
Originally posted by devmage:
I've already seen statements that sugest the G5 doesn't support the 2Gig modules because they weren't widely available (Though I see them on pricewatch.com) but that the machine will be able to support them. That increases the G5's configurable ram to 16Gigs
That's the kind of thing I'm talking about, yes.

I bought a "beige" G3 5 years ago. According to its documentation, it could take up to 192MB (64MB * 3) of memory. The reason was that the parts AT THE TIME were too big to fit at larger capacities, but the machine was actually designed to handle up to 768MB (256MB * 3).

So I want to find out how many actual addressing bits Apple implemented. If the answer is 43 (1GB * 8), then that's fine, but it could very well be more.
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Eug
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Sep 17, 2003, 01:57 PM
 
So I want to find out how many actual addressing bits Apple implemented. If the answer is 43 (1GB * 8), then that's fine, but it could very well be more.
That would be 33 not 43. However, for the wrong reason, you're close. Addressing is 42 bit in OS X I believe. 42-bit = 4398046511104 = 4 Terabytes. Should be enough for a while.

As for hardware, according to Apple's documentation, it's built to support 2 GB modules up to a total of 16 GB. No mention anything more than that. By the time you'll need more than 8 GB though, you'll want a new machine anyway so it's probably irrelevant.
     
denim  (op)
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Sep 17, 2003, 02:00 PM
 
Originally posted by Eug:
That would be 33 not 43. However, for the wrong reason, you're close. Addressing is 42 bit in OS X I believe. 42-bit = 4398046511104 = 4 Terabytes. Should be enough for a while.
Wait... you're right. I was a little off. I misremembered. It's: 10-bit for 1K, 20-bit for 1M, 30-bit for 1G. So allowing another 3 bits for the 8 multiplier, that's 33-bit, not 43. Oops. 43 bits would be 8T.

As far as I know, we're still at "32-bit clean", not more, BTW. That's the next thing.

As for hardware, according to Apple's documentation, it's built to support 2 GB modules up to a total of 16 GB. No mention anything more than that. By the time you'll need more than 8 GB though, you'll want a new machine anyway so it's probably irrelevant.
"want", perhaps. "afford"... quite a different thing. I happen to be fairly flush at the moment, but after I buy this computer and a replacement car, I won't be.
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devmage
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Sep 17, 2003, 02:28 PM
 
Originally posted by Eug:
That would be 33 not 43. However, for the wrong reason, you're close. Addressing is 42 bit in OS X I believe. 42-bit = 4398046511104 = 4 Terabytes. Should be enough for a while.

As for hardware, according to Apple's documentation, it's built to support 2 GB modules up to a total of 16 GB. No mention anything more than that. By the time you'll need more than 8 GB though, you'll want a new machine anyway so it's probably irrelevant.
That's interesing, if they support it now then why don't they plaster support for 16Gigs of memory everywhere rather than 8gigs? I know its a mute point as not many people would need more than 8gigs of ram but 16 just sounds so much bigger From a marketing standpoint I'd say they were missing an opportunity if it does already support the 2gig modules.

Of course as of right now its $745 per 2Gig PC3200 DIMM on pricewatch, so that would be $5960 worth of ram :b Plus the cost of your new G5. Still sounds tasty
     
Catfish_Man
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Sep 17, 2003, 04:42 PM
 
The PowerPC 970 uses 42 bit addressing. The UniNorth 3 Northbridge uses 36 bit addressing. The G5 supports up to 16GB of ram with 2GB chips (I don't know of any larger ones).
     
denim  (op)
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Sep 17, 2003, 07:35 PM
 
Originally posted by Catfish_Man:
The G5 supports up to 16GB of ram with 2GB chips (I don't know of any larger ones).
So far there probably aren't any, per se. But there will be.
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