Date: Tue, 8 Feb 2005 01:25:01 +0100 From: lovek <[EMAIL PROTECTED]>
seems like som ramsellers sell ram that works and others do not, it will all be recognized but hangs or freezes of some bad 128 has been reported.
Velocity Upgrades who seem to be gone now, sold quite a number of defective 128 MB DIMMs. To their credit, the price on 128 MB DIMMs was stuck well above $100 until they came on the scene and their first several batches were quality stuff. But they went downhill after that.
RAM can be insidious. Just because a machine boots with it installed does not mean that the RAM is any good. It's entirely possible that your computer never accessed the defective bits.
Testing with something like Ramometer (also included in GuagePro) has its problems because the portion of the RAM occupied by the operating system and program are never tested by the program.
Finally, a cell in the RAM may not be simply defective. It may only malfunction when surrounded by a certain pattern of 1s and 0s in the surrounding cells. This kind of failure is more rare but I've run across it. So testing with multiple patterns in memory is necessary.
We developed a test method over on the SuperMacs list that we call the RAM sandwich. First, test with RAM only in Bank A or only in Bank B but not in both. Then put known good DIMMs in slots 1 and 4. Then put the DIMM to be tested in slots 2 or 3. Now run RAMometer (or the equivalent in GuagePro) for about 1500 iterations (overnight). I've seen failures as high as 1200+ iterations, so running just a few hundred iterations is not enough. I suspect that RAMometer cycles different patterns through memory as it runs.
Most failures will occur within the first 100 iterations, but there are those rare ones up over the 1000 mark.
To find known good RAM, perform the above test with unknown RAM. If the test is passed, you know that the DIMM in the center slot (2 or 3) is good. It is a known good DIMM. However, you still know nothing about the DIMMs in slots 1 or 4. They were not tested in their entirety. If the test fails, you don't know which of the three failed. Try again with a different arrangement.
Date: Mon, 07 Feb 2005 22:19:05 -0500 From: Colin <[EMAIL PROTECTED]>
So... has anyone tested 256 MB sticks (if they even exist)? Just wondering...
As far as I know no one ever made a 256 MB DIMM. However, the Apple Hardware Developer Notes for the 7200 claims that the maximum theoretical DIMM size in the 7200 is 256 MB. This is interesting, because if there were 256 MB DIMMs one could then take the 7200 up to 1 GB of RAM, the same as the 7500/8500.
The Hardware Developer Notes for the 7/8/9500 says that 128 MB is the largest supported DIMM in those machines, but the addressing modes listed suggest that a 256 MB DIMM might work if you could find one.
There should be little surprise that 1 GB works in the 8500, as the 9500 has twelve DIMM slots and 1.5 GB of RAM works in that machine. I think that 1.5 GB is the most supported by the memory map of the machine, though I could be mistaken and it might go to 2 GB.
However, IIRC, some earlier versions of the OS, which run on the 9500, do not support more than 1 GB of RAM. I'm not sure about that recollection, but it's a faint inkling at the back of my mind.
The Umax S900 (same architecture/chipset as the 7/8/9500) has 16 MB soldered to the motherboard and eight DIMM slots. If you fill it up, you get 1 GB + 16 MB of RAM installed or 1040 MB of RAM.
Jeff Walther
-- PCI-PowerMacs is sponsored by <http://lowendmac.com/> and...
Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Sonnet & PowerLogix Upgrades - start at $169 | & CDRWs on Sale! |
Support Low End Mac <http://lowendmac.com/lists/support.html>
PCI-PowerMacs list info: <http://lowendmac.com/lists/pci-powermacs.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[email protected]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/pci-powermacs%40mail.maclaunch.com/>
iPod Accessories for Less at 1-800-iPOD.COM Fast Delivery, Low Price, Good Deal www.1800ipod.com
