The LaserWriter 12/640 PS printer ships with 4MB of RAM. Installing additional memory provides additional features.
| RAM Installed | Options Available |
| 4MB (Standard) | None. You cannot access either PhotoGrade or duplex printing. |
| 12MB | You can enable either PhotoGrade OR duplex printing. |
| 20MB | You can enable both PhotoGrade and duplex printing. Duplex printing is available up to US letter. |
| 24MB and greater | You can enable both PhotoGrade and duplex printing. Duplex printing is available for all paper sizes including US legal. |
Note: Additional memory also enables you to download additional fonts and provides greater document caching.
RAM Upgrade Specifications
To increase the printer's RAM, purchase SIMMs with the following specifications:
SIMM Dimensions- Length: 107.95 mm +/- 0.20 mm (4.25 in. +/- .008)
- Height: 25.53 mm (1.005 in.) maximum
SIMM Sizes and Speeds
| SIMM Size | Configuration | Speed | Connector type |
| 4 MB SIMM | 1 M X 32 bit (one 4 MB bank) | 70 ns or less | 72-pin |
| 8 MB SIMM | 2 M X 32 bit (two 4 MB banks) | 70 ns or less | 72-pin |
| 16 MB SIMM* | 4 M X 32 bit (one 16 MB bank) | 70 ns or less | 72-pin |
| 32 MB SIMM* | 8 M X 32 bit (two 16 MB banks) | 70 ns or less | 72-pin |
| * Must have a 2 KB row (11 bit x 11 bit) refresh configuration. 16 MB SIMMs with a 4 KB row (10 bit X 12 bit) refresh configuration are not compatible with the printer. |
Installing RAM
Your printer comes with 4 MB of RAM installed in Bank A/B. The table below lists RAM configurations you can use.
Amount of Memory
(megabytes) | Bank C/D
(left slot) | Bank A/B
(right slot) |
| 4 MB | 0 MB | 4 MB |
| 8 MB | 4 MB | 4 MB |
| 0 MB | 8 MB |
| 12 MB | 4 MB | 8 MB |
| 8 MB | 4 MB |
| 16 MB | 8 MB | 8 MB |
| 0 MB | 16 MB |
| 20 MB | 4 MB | 16 MB |
| 24 MB | 8 MB | 16 MB |
| 32 MB | 16 MB | 16 MB |
| 0 MB | 32 MB |
| 36 MB | 4 MB | 32 MB |
| 40 MB | 8 MB | 32 MB |
| 48 MB | 16 MB | 32 MB |
| 32 MB | 16 MB |
| 64 MB | 32 MB | 32 MB |
Note: Pages 152-158 in the LaserWriter 12/640 User's Guide provides detailed instructions on installing additional memory in your LaserWriter printer.