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Macintosh Color Classic II Memory Upgrade Guide

From RetroTechCollection
The LC 550/575 logic board in Apple's Memory Guide, with the single 72-pin DRAM SIMM slot and the VRAM SIMM slot marked. Color Classic II boards examined by owners are this design.

The Macintosh Color Classic II and the Macintosh Performa 275 have 4 MB of RAM soldered to the logic board. How much more they take depends on which of Apple's documents is right, and the board in the machine settles it. Apple's service manual describes the Color Classic's two 30-pin connectors and a 10 MB maximum; Apple's specification page describes one 72-pin socket and 36 MB.[1][2]

Which board is fitted

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Apple's documents disagree:

  • The Color Classic II/Performa 275 Service Source repeats the Color Classic's memory pages: one slot J10 with two 30-pin connectors, filled in pairs, 100 ns, 10 MB maximum, and 256K of VRAM expandable to 512K with a 256K VRAM SIMM in J9.[1] Apple's Memory Guide (May 2000) gives the same.[3]
  • Apple's technical specification page gives one 72-pin SIMM slot, 80 ns, 4 to 36 MB and a 32-bit data path.[2] Low End Mac gives the same and says the Color Classic II and the Performa/LC 550 share a motherboard.[4]
  • Userlandia compared boards from Japanese Color Classic IIs with LC 550 boards. All carried board number 820-0368-A, the LC 550 board, with four VRAM chips making 512K on the board, and gave thousands of colours without a VRAM SIMM. Userlandia also reports that Apple's June 1994 Service Module Identification Manual lists one logic board, 661-1830, for both the LC 550 and the Color Classic II.[5] The exploded view in the Color Classic II Service Source also gives 661-1830.[1]

Look before buying memory. Slide the board out (see below) and check the socket next to the soldered RAM. One long 72-pin socket means the LC 550 board and the rules in the next section. A pair of short 30-pin connectors means the Color Classic arrangement; follow the Macintosh Color Classic Memory Upgrade Guide.

LC 550-type board (72-pin)

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Apple's Memory Guide entry for the LC 550 gives:[3]

  • 4 MB soldered DRAM.
  • One 72-pin SIMM slot, 80 ns or faster. SIMMs go in singly; sizes 1, 2, 4, 8, 16 and 32 MB.
  • 36 MB maximum.
LC 550 RAM configurations (Apple Memory Guide)[3]
Total RAM SIMM fitted
4 MB none
5 MB 1 MB
6 MB 2 MB
8 MB 4 MB
12 MB 8 MB
20 MB 16 MB
36 MB 32 MB

VRAM

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The LC 550 board has 512K of VRAM soldered and one VRAM SIMM slot.[3][5] Sources differ on the maximum:

  • Apple's Memory Guide LC 550 entry and the Macintosh LC 520/550/575 Service Source give 1 MB, reached with one 512K VRAM SIMM.[3][6]
  • The Memory Guide LC 520 entry, for a board with the same number according to Userlandia, gives 768K with one 256K VRAM SIMM rated 80 ns or faster, and Userlandia gives 768K for the Color Classic II.[3][5]

If the Monitors control panel already offers thousands of colours on the built-in screen with no VRAM SIMM fitted, the board has the 512K of soldered VRAM.[5]

Procedure

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The logic board comes out through the I/O door at the back. Apple lists no preliminary steps, and the case and CRT are not disturbed.[1]

  1. Switch off and unplug the machine. Wear an earthed wriststrap and work on an earthed mat.[1]
  2. Remove the two security screws from the I/O door, if fitted. Push down the two latches until the door snaps open, and take it off.[1]
  3. Grasp the logic board firmly with both hands and pull it straight out of the chassis.[1]
  4. Hold the SIMM by its edges with the contacts pointing down, insert it at an angle into the socket, and push it back until it snaps into place.[1] On a 30-pin board, fill both connectors.
  5. Fit a VRAM SIMM, if used, the same way in the VRAM slot.[1]
  6. Slide the board back in and check that no bent metal tab on the chassis can touch the underside of the board and short it.[1]
  7. Start up and check the total in About This Macintosh.

Common problems

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Symptom Likely cause Action
30-pin SIMMs bought, but the board has one long socket (or the reverse) The two memory layouts described above Check the board before ordering[1][2]
Sad Mac icon at startup Bad disk or bad SIMM Apple's order: known-good disk, then the RAM SIMMs, then the logic board[1]
Sad Mac with black vertical lines and a screeching sound Bad SIMM Replace the RAM SIMMs, then the logic board[1]
Machine dead after refitting the board Board shorted on a bent chassis tab, or board not fully home Pull the board, straighten the tab, reseat[1]

Sad Mac codes are decoded on Sad Mac Error Codes and with the Sad Mac Decoder.

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References

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  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 Apple Computer, Macintosh Color Classic II/Performa 275 Service Source, hosted here as File:Color classic ii.perf 275.pdf (see Macintosh Color Classic II/ Performa 275 Service Source). Specifications: Memory pp. 3-4 (PDF pp. 7-8), Sound and Video p. 9 (PDF p. 13); Take Apart: Logic Board pp. 1-4 (PDF pp. 36-39); Upgrades: VRAM Upgrade (PDF pp. 78-79), Memory Upgrade (PDF pp. 83-85); Symptom Charts: Miscellaneous p. 17 (PDF p. 34); Exploded View (PDF p. 137).
  2. ↑ 2.0 2.1 2.2 Apple, "Macintosh Color Classic II: Technical Specifications" (retrieved 2026-10-02). Data path 32 bits at 33 MHz; logic board 4 MB; one 72-pin SIMM slot; 4-36 MB; 80 ns minimum; SIMM sizes 1, 2, 4, 8, 16, 32 MB; install in groups of 1; "This system is not sold in the U.S."
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 Apple Computer, Apple Memory Guide (May 2000), hosted here as File:Apple Memory Guide (May 2000).pdf (see Apple Memory Guide). Early Macintosh p. 8, Color Classic II (PDF p. 11); Macintosh LC p. 6, LC 520 (PDF p. 36); Macintosh LC p. 7, LC 550/575 (PDF p. 37).
  4. ↑ Low End Mac, "Mac Colour Classic II (Performa 275)" (retrieved 2026-10-02). RAM 4 MB, expandable to 36 MB using a single 80 ns 72-pin SIMM; shares its motherboard with the Performa/LC 550. Secondary source.
  5. ↑ 5.0 5.1 5.2 5.3 Userlandia, "How Much Video Memory Does A Mac Color Classic II Have, Anyway?" (retrieved 2026-10-02). Board ID 820-0368-A in Color Classic II, Performa 275 and LC 550 machines; 512K VRAM on board, 768K with a 256K VRAM SIMM; 661-1830 for LC 550 and CC II in Apple's June 1994 Service Module Identification Manual. Secondary source: one owner's examination of several boards.
  6. ↑ Apple Computer, Macintosh LC 520/550/575 Service Source, hosted here as File:Lc_520.550.575.pdf. Specifications: Memory pp. 2-3 (PDF pp. 8-9): 4 MB on board, expandable to 36 MB, 72-pin DRAM SIMM connector; 512K VRAM on board, expandable to 1 MB.


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