New iMac, iMac DV, and iMac Special Edition


We appreciate your technical corrections and comments !

The "slot-loading" iMac, iMac DV, and iMac Special Edition all share the same logic board, which contains two expansion DIMM slots. These slots accept either 64MB or 128MB DIMMs using 64-Mbit technology, or 128MB or 256MB DIMMs using 128-Mbit technology. All SDRAM DIMMs used in the New iMac DV family must be 3.3 volt (V), unbuffered, 64-bit wide, 168-pin, with correctly programmed Serial Presence Detect EPROM. SDRAM speed must be 100MHz, 10ns or faster (meaning a lower number). These slots support up to 512MB of PC100 SDRAM (999MB maximum per application program).

The "slot-loading" iMac shipped standard with 64MB main memory. The iMac DV also shipped with 64MB, but the iMac Special Edition shipped with 128MBs SDRAM standard.

Note: SDRAM DIMMs may be installed one at time and in any slot, as memory interleaving is not supported (no benefit accrues from installing SDRAM DIMMs in matched pairs). We do advise, if you are installing 128MB DIMMS, that you ensure that they have been qualified for use in the iMac DV.

Important: RAM expansion DIMMs for the iMac family of computers must be PC-100 compliant and use SDRAM devices. Improperly installed EDO or SGRAM devices will cause the computer will beep several times when the user attempts to restart the computer.

The SDRAM devices used in the RAM expansion modules must be self-refresh type devices intended for operation with a 3.3v power supply. MacGurus recommends the use of SDRAM devices running at 125MHz or faster, corresponding to a cycle time of 8ns or less, as posited by the PC-100 specification.



Logic Board Battery

Important: It is advisable to remove the logic board battery when handling the logic board. Ensure proper ESD procedures are followed when handling modules.

The battery on the logic board preserves stored system settings, such as date and time. It is only necessary to test the battery when you cannot power on the computer, or the date and time are reset every time AC power is removed.

The battery is also used to power the PMU chip (the PMU chip keeps time and must always be running) when the computer is unplugged from the your power strip (AC power). The PMU is very sensitive and touching any circuitry that is connected to the PMU can cause it to crash. If the PMU crashes, battery life is reduced from approximately five years to about two days, unless the PMU is reset. Once the battery fails, the PMU will reset the time and date to 12:00 AM 1/1/04 every time AC power is removed. To remedy this situation, replace the battery and reset the PMU.

If the iMac presents a "No Power" situation, check the battery before replacing modules. When checking the battery, ensure the computer is unplugged. Measure the voltage across the battery's BT1 positive and ground terminals. The battery should read 3.3 volts to 3.7 volts. If itçs lower than 3.2 volts, replace the battery and reset the PMU.

Note: The iMac uses a lithium battery that must be disposed of in accordance with hazardous waste regulations.


Specifications:
Logic Board RAM None
Supported DIMMs 64MB, 128MB (both 64-Mbit), and 128MB, 256MB (all 128-Mbit).
Number DIMM Slots Two(2)
Supported VRAM 8 MB SGRAM soldered on the board
Number VRAM Slots None
L2 Cache Supported? 512K Backside Level 2 cache
DIMM Type PC100 SDRAM 3.3-volt, 64-bit wide, 168-pin.




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