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512 + 1GB =???
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Joined: 25 Apr 2006
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PostPosted: Thu Jun 01, 2006 5:46 am    Post subject: Reply with quote

Here's why Apple recommends matched memory, espeically in the integrated video Mini and MacBook:

Mobile Intel 945 Express Chipset Family Datasheet


Page 331

Dual-channel Symmetric Mode

This mode provides maximum performance on real applications. Addresses are between the channels, and the switch happens after each cache line (64-byte boundary). The channel selection address bit is controlled by DCC[10:9]. If a second request sits behind the first, and that request is to an address on the second channel, that request can be sent before data from the first request has returned. Due to this feature, some progress is made even during page conflict scenarios. If two consecutive cache lines are requested, both may be retrieved simultaneously, since they are guaranteed to be on opposite channels. The drawback of Symmetric mode is that the system designer must populate both channels of memory so that they have equal capacity, but the technology and device width may vary from one channel to the other.

Dual-channel Asymmetric

This mode trades performance for system design flexibility. Unlike the previous mode, addresses start in channel A and stay there until the end of the highest rank in channel A, then addresses continue from the bottom of channel B to the top. Real world applications are unlikely to make requests that alternate between addresses that sit on opposite channels with this memory organization, so in most cases, bandwidth will be limited to that of a single channel. The system designer is free to populate or not to populate any rank on either channel, including either degenerate single-channel case.

Page 353

The entire IGD [Integrated Graphics Controller] is fed with data from its memory controller. The GMCH's graphics performance is directly related to the amount of bandwidth available. If the engines are not receiving data fast enough from the memory controller (e.g., single-channel DDR2 553), the rest of the IGD will also be affected.
1.66GHz Core-Duo Mini, 2GB/120GB, Apple 23" Cinema HD Display
Apple Wireless Keyboard & Mouse, Apple iSight Camera
Apple USB Modem (for faxing), Bose Companion 2 Speakers
2.0GHz white MacBook 1GB/80GB
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Joined: 14 Apr 2006
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PostPosted: Tue Jul 11, 2006 4:26 pm    Post subject: Reply with quote

But in my case, I will most likely get my imac with the single 1GB module. Later on, I would just get another 1GB stick. this way I would not "waste" any of the memory that came with my imac.
Hector David Salinas
San Pedro Sula, Honduras

Current PC: (yes a PC, But I am getting a mac soon)
P4 2.4ghz (Northwood)
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Joined: 26 Jul 2006
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PostPosted: Wed Jul 26, 2006 8:55 am    Post subject: Symmetric Ram Reply with quote

I had a intel mini with 1GB + 256MB. I was suffering from very poor OpenGL performance, and I read here that maybe the problem could be matched pairs... I went running to get another GB of ram, installed it, and same poor performance in OpenGL. In fact I dont feel no better performance in others areas or apps... So I think that "symmetric" thing is not really a bout real world performance...
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