Description
Included in the sale: Fully assembled and tested RAM Card only, no additional wires are provided.
This is an all-new-components RAM upgrade card for the Macintosh Portable!
It provides 7 megabytes of extra RAM, for a total of 8 megabytes on the M5120 Portable.
On the M5126 (Backlit) Portable, it has been tested to provide 4MB of expansion for 5MB total. To get more than that, you must tap into the /AS line on the PDS expansion slot, which is an exercise left to the reader. Instructions for doing this are below in “Connecting to #AS”.
This card is probably due for a redesign now that the XC9536XL CPLD series is discontinued. Stock will be “spotty” due to the discontinuation.
Important Note:
It has been noted that larger RAM cards cause some CPU performance degradation and substantial slowdown after coming out of sleep mode (Special menu > Sleep).
I have investigated these issues and discovered that the RAM card itself is not at fault.
- CPU perf degradation comes from the larger memory space (above 3MB of expansion on the M5126, and above 4MB of expansion on the M5120)
- Memory manager has to calculate more things with larger RAM space, costing time and some CPU performance
- Sleep issue is caused by a bug in how the Portable’s “CPU Glue” chip communicates with the rest of the system
- This is crazy, allowing up to 8 megabytes of expansion memory and then missing a bug which cuts perf after sleep
- After restarting, the performance decrease goes away (but it comes back after sleep)
Installation:
First, remove all sources of power! This includes main battery (If using a Battery Eliminator, install the “Discharge” resistor and allow to drain overnight – be sure to remove the discharge resistor after installing the RAM card), PRAM battery, and power adapter.
This card is designed to work with both models of Portable, and there’s enough wiggle room to move around by a single row of pins. Please ensure that all the pins are lined up properly before re-applying power!
Startup will take noticeably longer in 7MB mode and somewhat longer in 3MB or 4MB mode, as the memory test must now check substantially more RAM.
Connecting to #AS (for Backlit Portables):
- On the RAM card, remove the jumper labeled #AS
- Use a female to male 2.54mm jumper wire (the shortest one you have available) to connect to one of the two following points:
- PDS Slot Row C Pin 8
- ROM Slot Pin 28
- On the RAM card, connect that jumper wire to the bottom pin where the jumper was removed (right next to the #AS silkscreen)
The Portable PDS Slot has silkscreen indicating which row is C and where Pin 1 is. Pin 1 is closer to the SCSI port, and then just counts up. 1, 2, 3, 4, 5 and so on in each row.
The ROM Slot also has silkscreen indicating numbering, but it’s different from the PDS. Pin 1 and 2 are right by the “ROM” silkscreen, and each row is for either only even or odd numbers. So you want to use the even numbered side and it counts up 2, 4, 6, 8 while the odd side counts up 1, 3, 5, 7.
