The ram test failure message pops up because . . . the ram failed the startup ram test. By rebooting, you avoid getting the message because the ram test is not performed on a reboot. You are more likely to experience problems though once the OS starts actually using the 'problem' ram.
I've had my eye on this thread and other similar threads in the past because I've got more than 80 (!!) 24MB ram modules I'm unable to sell until I can figure out why they don't work in some 1400s, but _do_ work fine in others _and_ how to fix it. I've read everything I could find on the net, in list archives, in NGs, etc. but the best info I've seen so far can be found in the Apple devnote on the second generation 1400: ------------------------------------------------------------------- RAM Expansion Guidelines Developers must take special care when designing RAM expansion cards for the PowerBook 1400 computers. Excessive capacitive loading on the memory address bus can cause a problem with the timing margins. When this problem occurs, the computer displays a dialog box at startup time warning the user that the memory test has failed, and the computer does not recognize a portion of the newly-installed expansion RAM. Address Signal Timing For proper operation of the expansion RAM, the signals on the memory address bus must be stable before the assertion (falling edge) of the RAS (row address strobe) signals. Because each address line is connected to every DRAM device, whereas each RAS line is connected to only one bank of devices, the difference in loading can cause the address signals to change more slowly than the RAS signals. The resulting decrease in the timing margins is greater on expansion cards that have many DRAM devices. � Note: The interface to the RAM expansion slot uses buffers to provide adequate fan-outs. Signals RMA(0�11), /RCAS(0�3), /RRAS(2�7), and /RRAMWE are buffered by 74FCT245 devices and 22 � damping resisters. � The timing margin between the address signals and the assertion of the RAS signals is small. Additional loading of the address bus signals will further decrease the timing margins and, under worst-case conditions, will force negative timing margins on the RAM expansion card. To maintain adequate timing margins in the worst case�using DRAM devices from different manufacturers and considering the timing delay caused by circuit loading�requires an additional delay of 7 to 10 nS in the assertion of the RAS signals. The next section describes two ways of obtaining this additional delay. [more stuff] ------------------------------------------------------------------- sources here: <http://developer.apple.com/techpubs/hardware/Developer_Notes/Macintosh_CPU s-PPC_Portable/PowerBook_1400.pdf> <http://developer.apple.com/techpubs/hardware/Developer_Notes/Macintosh_CPU s-PPC_Portable/PowerBook_1400_Addendum.pdf> One thing for sure, the first devnote has none of this detail, so obviously Apple was catching some heat from ram makers and customers when supposedly compatible ram turned out to be incompatible. I've just about given up hope though that I'll be able to fix the modules I've got, a shame since there's still a good market for the darn things. Ce la vie. : >) Dan K On 9/11/02 archy <[EMAIL PROTECTED]> wrote: > >I bought my 1400c/133 in February of 1997, and it has the 8MB "expansion" >board, so 16 MB on the board. I promptly bought two 24 meg stackable >cards. >I installed both, and upon startup, got the memory check error, and have had >it ever since. From a cold start-up, I can click continue and go onto the >finder, and when I select About this Macintosh..., the computer only >recognizes 60 MB. Next, I select Restart, and everything boots properly, >memory check is fine, and then I get the full 64MB. So my guess is that >on a >cold boot, not all the stacks of memory get powered-up in time for memory >check. And yes, when I remove one of the 24 MB cards, the cold-boot is >hitch-free. > >I guess this would be a good time to ask if there is a way for me to delay >the >memory check long enough for the memory stacks to completely power-up. > >-Peter > > >>===== Original Message From Malcolm Cornelius <[EMAIL PROTECTED]> >===== > >>I have heard of this problem but never seen it myself, and I've upgraded a >>few 4MB to 8MB. >> >>My instinct would have been incompatible stackable cards or a bad 8MB card, >>can anyone shed any more light on this one ? -- PowerBooks is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Enter To Win A | -- Canon PowerShot Digital Cameras start at $299 | Free iBook! | Support Low End Mac <http://lowendmac.com/lists/support.html> PowerBooks list info: <http://lowendmac.com/lists/powerbooks.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/powerbooks%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
