Is there a way to check RAM bus width?

Member
Posts: 469
Joined: 2002.10
Post: #1
I just swapped out the 512MB dimm in my MBP for a matching 1GB. The system profiler shows 2GB. Is there a way to see if I'm getting the full bandwidth for the dual channel pair?

---Kelvin--
15.4" MacBook Pro revA
1.83GHz/2GB/250GB
Quote this message in a reply
Luminary
Posts: 5,143
Joined: 2002.04
Post: #2
Well, the CPU can't use it for a start, so it's probably only of limited relevance Wink
Quote this message in a reply
Member
Posts: 469
Joined: 2002.10
Post: #3
really? elaborate please.

---Kelvin--
15.4" MacBook Pro revA
1.83GHz/2GB/250GB
Quote this message in a reply
Sage
Posts: 1,482
Joined: 2002.09
Post: #4
There was talk on the IRC channel a week ago or so. Apparently the extra bandwidth goes to anything but the processor. The GMA950 in the MacBook can use the extra bandwith for graphics. I wouldn't be surprised if it would allow other devices that use DMA to access the memory though.

Scott Lembcke - Howling Moon Software
Author of Chipmunk Physics - A fast and simple rigid body physics library in C.
Quote this message in a reply
Luminary
Posts: 5,143
Joined: 2002.04
Post: #5
The Core Duo is on a 667MHz FSB, at the same width as the RAM, I believe. That means that the maximum data rate the CPU can utilize is that of a single channel. Of course, DMAs from the video card or other devices could utilize additional bandwidth, but the chance that that occurs at the same time as the CPU is trying to use 100% of the bandwidth is small...

When the machine has a GMA 950 and is using system memory for graphics, there is a substantial benefit to the dual-channel, since the graphics imposes significant additional overhead.

That is why Apple is shipping a single SO-DIMM and an empty slot in Core Duo machines with dedicated video memory, and matched pairs of SO-DIMMs in the machines with integrated graphics.
Quote this message in a reply
Post Reply 

Possibly Related Threads...
Thread: Author Replies: Views: Last Post
  Check out the PC vs. Macs in this Game Dev meeting. WhatMeWorry 7 4,268 Nov 16, 2006 11:28 AM
Last Post: ravuya