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2.5mb table had wrong ram values 512kb and should have been 256kb as I have edited.
Sourced to Apple Macintosh SE Service Source + Guide to the Macintosh Family Hardware: split resistor-board (R35/R36) and jumper-board procedures properly, added Apple note to disregard the 2/4M silkscreen, added eight-chip/complete-row/row-order rules, removed emoji headings, refs and reflist
 
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The '''Macintosh SE''' utilizes '''30-pin SIMM (Single Inline Memory Module) chips''' and supports the following configurations:
The '''[[Macintosh SE]]''' takes 30-pin SIMMs in four sockets and supports a maximum of '''4 MB'''.<ref name="ssse">Apple Computer, ''Macintosh SE Service Source'' — Specifications (Memory) and Upgrades (Memory Upgrade) chapters. Hosted on this wiki: [[:File:Macintosh se.pdf]].</ref> Machines shipped with either 1 MB or 2 MB fitted.<ref name="ssse" />


<templatestyles src="Template:StyledTable/styles.css" />
== Which logic board do you have? ==
{| class="wikitable styled-table" style="width:60%; text-align:center;"
 
|+ '''Macintosh SE RAM Configurations'''
'''This matters, because the two board revisions are configured differently.'''<ref name="ssse" />
|-
 
! Total RAM !! SIMM Configuration !! Individual SIMM Capacity
* '''Resistor boards''' (earlier). A solder-type resistor identifies the memory configuration: '''R35''' is fitted for 1 MB and '''R36''' for 2 MB. In Apple's hardware documentation these are the '''256K BIT''' (R35) and '''ONE ROW''' (R36) positions in the RAM SIZE area.<ref name="gtmfh">Apple Computer, ''Guide to the Macintosh Family Hardware'', 2nd edition, Addison-Wesley, 1990, Chapter 5 "Memory", pp. 196–198 — SIMM rules, RAM SIZE resistors and the later jumper for the Macintosh SE.</ref>
|-
* '''Jumper boards''' (later). A jumper in one of two positions, labelled '''2/4M''' and '''1M''', does the same job.<ref name="gtmfh" />
| 1 MB (stock) || 4 × 256 KB || 256 KB
 
|-
== Memory specifications ==
| 2 MB || 4 × 512 KB || 512 KB
 
|-
* '''SIMM type:''' 30-pin, '''150 ns or faster'''; the −xx suffix after the manufacturer's part number gives the speed, so −15 is a 150 ns part.<ref name="ssse" />
| 2.5 MB || 2 × 256 KB + 2 × 1 MB || Mixed (256 KB & 1 MB)
* '''Eight RAM ICs per SIMM.''' A nine-chip module works but the ninth device is not connected.<ref name="gtmfh" />
|-
* '''SIMMs go in rows of two'''; a row is either empty or full.<ref name="gtmfh" />
| 4 MB (maximum) || 4 × 1 MB || 1 MB
* All the RAM ICs in a row must be the same size and speed.<ref name="gtmfh" />
|}
* On a resistor board the larger SIMMs go in '''row 1'''; on a jumper board they go in '''row 2'''.<ref name="gtmfh" />
* '''Maximum: 4 MB.'''<ref name="ssse" />
 
== Upgrades, by board type ==
 
=== Resistor board ===
Clip one end of resistor '''R35''' or '''R36''' and bend the resistor away from the clipped lead — clipping rather than desoldering lets it be tacked back later.<ref name="ssse" />


* The '''Macintosh SE''' requires SIMMs with '''150 ns or faster''' access time.
* '''2.5 MB:''' two 1 MB SIMMs in slots 1 and 2, two 256K SIMMs in slots 3 and 4.<ref name="ssse" />
* '''All four SIMM slots must be populated with memory of the same capacity''' unless using a '''2.5 MB mixed configuration'''.
* '''4 MB:''' four 1 MB SIMMs in slots 1 to 4.<ref name="ssse" />
** If using the '''2.5 MB configuration''', install the 1 MB SIMMs in Slots 1/2 and 256 KB SIMMs in Slots 3/4.
* If using '''1 MB SIMMs''', '''you must clip the R35 resistor''' on Rev 1 logic boards, or, move the jumper in the same location on Rev 2 boards.
[[File:Mac SE (Soldered) Guide.png|none|thumb|520x520px|Macintosh SE (Soldered) Memory Upgrade Guide]]
[[File:Mac SE (Jumper) Guide.png|none|thumb|518x518px|Macintosh SE (Jumpers) Memory Upgrade Guide]]


== 🛠 Required Tools ==
=== Jumper board ===
* '''1 MB to 2.5 MB:''' remove the two 256K SIMMs from slots 3 and 4, fit two 1 MB SIMMs there, and remove the jumper permanently.<ref name="ssse" />
* '''1 MB to 4 MB:''' remove all four 256K SIMMs, fit four 1 MB SIMMs, remove the jumper permanently.<ref name="ssse" />
* '''2 MB to 2.5 MB:''' fit two 256K SIMMs in slots 1 and 2 and remove the jumper permanently.<ref name="ssse" />
* '''2 MB to 4 MB:''' fit two 1 MB SIMMs in slots 1 and 2 and remove the jumper permanently.<ref name="ssse" />


To upgrade the Macintosh SE memory, you will need:
'''Apple's note: disregard the "2/4 M" label silkscreened on the board. A 4 MB upgrade requires the jumper to be removed.'''<ref name="ssse" />


* '''Torx T15 screwdriver''' (for case removal)
[[File:Mac SE (Soldered) Guide.png|none|thumb|520x520px|Macintosh SE, resistor-type logic board]]
* '''Plastic spudger''' or '''pry tool''' (to carefully separate the case)
[[File:Mac SE (Jumper) Guide.png|none|thumb|518x518px|Macintosh SE, jumper-type logic board]]
* '''Anti-static wrist strap''' (to prevent electrostatic discharge)
* '''Compatible 30-pin SIMMs''' (matching capacity and speed)


== 🔧 Memory Upgrade Procedure ==
== Tools ==
* T15 Torx screwdriver (long shaft)
* Case separator or plastic spudger
* Anti-static wriststrap
* Matching 30-pin SIMMs


'''Step 1: Prepare the Macintosh SE'''
See [[Recommended Tools]].
Ensure the Macintosh SE is completely powered off and unplugged. Work on a grounded surface and wear an anti-static wrist strap to protect components from static discharge.


'''Step 2: Remove the Case'''
== Procedure ==
Use a Torx T15 screwdriver to remove the four screws securing the rear case. Carefully separate the two halves using a plastic spudger. Be cautious of the CRT, as it retains high voltage even when unplugged.


'''Step 3: Locate the SIMM Slots'''
'''1. Prepare.''' Power off, unplug, work on a grounded surface.
The memory slots are on the logic board, positioned near the rear ports. You'll need to slide the logic board out from the bottom metal chasis.


'''Step 4: Remove Existing SIMMs'''
'''2. Open the case.''' The machine contains a CRT: read [[CRT Discharge Procedure]], discharge the CRT to the ground lug before disconnecting anything, and do not fit a grounding wriststrap until after it has been discharged. Apple warns that failing to discharge first can damage the logic board or the analogue board.<ref name="ssse" />
If replacing existing memory, '''gently (they easily snap)''' push apart the retention clips on each side of the SIMM slot and remove the modules.


'''Step 5: Install New SIMMs'''
'''3. Withdraw the logic board''' from the bottom of the chassis to reach the sockets.
Align the new SIMMs with the slots, ensuring the notch on the side of the SIMM matches the keying of the slot. Firmly push down until the SIMM snaps into place.


* If upgrading to 4 MB using 1 MB SIMMs, clip the leg on the R35 resistor, or move the jumper on the logic board.
'''4. Remove the existing SIMMs.''' The retaining clips snap easily; ease them outward gently.
* If using a 2.5 MB mixed configuration, install 1 MB SIMMs in Slots 1/2 and 256 KB SIMMs in Slots 3/4.


'''Step 6: Reassemble the Macintosh SE'''
'''5. Fit the new SIMMs''' with the notch matched to the socket keying, filling complete rows.
Once the memory is installed, reassemble the case and secure it with the Torx screws.


'''Step 7: Verify the Upgrade'''
'''6. Set the resistor or jumper''' for the new configuration before reassembly.
Power on the Macintosh SE and check the memory count within the Finder. If the full capacity is not recognized, ensure:


* All SIMMs are properly seated.
'''7. Reassemble and verify''' the memory figure at startup.
* SIMMs are of matching speed and configuration.
* The correct resistor was clipped for 1 MB SIMMs.


== ❗ Common Issues and Troubleshooting ==
== Common problems ==


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{| class="wikitable styled-table" style="width:100%;"
{| class="wikitable styled-table" style="width:100%;"
! Symptom !! Likely cause !! Action
|-
|-
! Issue !! Possible Cause !! Solution
| Sad Mac, or a chime followed by nothing || Wrong, faulty or partly seated SIMMs || 30-pin, 150 ns or faster, eight-chip, non-parity, fully seated
|-
|-
| Macintosh SE beeps on startup || Incompatible or faulty SIMMs || Ensure SIMMs are '''30-pin, 150 ns or faster''', properly seated and (or) Non-Parity
| Sad Mac with the memory jumper suspected || Configuration not set || Apple's own chart says to verify the three-pin jumper is configured correctly before replacing anything<ref name="ssse" />
|-
|-
| Memory not recognized correctly || Mismatched SIMM capacities || Use '''four identical SIMMs''' or a supported 2.5 MB configuration.
| Memory figure unchanged || Resistor still fitted, or jumper still installed || Clip R35/R36, or remove the jumper, as above
|-
|-
| System crashes or instability || Faulty or damaged SIMMs || Replace with known-good, compatible memory modules.
| Half the expected memory || A row is half-populated, or the larger pair is in the wrong row || Fill rows completely and observe the row rule for your board type
|}
|}


== 📜 Additional Resources ==
Sad Mac codes are decoded on [[Sad Mac Error Codes]] and with the [[Sad Mac Decoder]]. Apple's chart also points at individual SIMMs for particular codes.<ref name="ssse" />


For further details, refer to:
== Related pages ==
* [[Macintosh SE]]
* [[Macintosh SE General Maintenance]]
* [[Macintosh SE Troubleshooting]]
* [[Macintosh SE Troubleshooting]]
* [[Macintosh SE General Maintenance]]
* [[Sad Mac Error Codes]]
* [[:Category:Apple Service Source|Apple Service Source]]
* [[:Category:Apple Service Source|Apple Service Source]]
== References ==
<references />


[[Category:Apple Vintage Computers]]
[[Category:Apple Vintage Computers]]
[[Category:Macintosh Memory Upgrades]]
[[Category:Macintosh Memory Upgrades]]
[[Category:Macintosh Hardware Upgrades]]
[[Category:Macintosh Hardware Upgrades]]

Latest revision as of 18:14, 23 September 2026

The Macintosh SE takes 30-pin SIMMs in four sockets and supports a maximum of 4 MB.[1] Machines shipped with either 1 MB or 2 MB fitted.[1]

Which logic board do you have?

[edit | edit source]

This matters, because the two board revisions are configured differently.[1]

  • Resistor boards (earlier). A solder-type resistor identifies the memory configuration: R35 is fitted for 1 MB and R36 for 2 MB. In Apple's hardware documentation these are the 256K BIT (R35) and ONE ROW (R36) positions in the RAM SIZE area.[2]
  • Jumper boards (later). A jumper in one of two positions, labelled 2/4M and 1M, does the same job.[2]

Memory specifications

[edit | edit source]
  • SIMM type: 30-pin, 150 ns or faster; the −xx suffix after the manufacturer's part number gives the speed, so −15 is a 150 ns part.[1]
  • Eight RAM ICs per SIMM. A nine-chip module works but the ninth device is not connected.[2]
  • SIMMs go in rows of two; a row is either empty or full.[2]
  • All the RAM ICs in a row must be the same size and speed.[2]
  • On a resistor board the larger SIMMs go in row 1; on a jumper board they go in row 2.[2]
  • Maximum: 4 MB.[1]

Upgrades, by board type

[edit | edit source]

Resistor board

[edit | edit source]

Clip one end of resistor R35 or R36 and bend the resistor away from the clipped lead — clipping rather than desoldering lets it be tacked back later.[1]

  • 2.5 MB: two 1 MB SIMMs in slots 1 and 2, two 256K SIMMs in slots 3 and 4.[1]
  • 4 MB: four 1 MB SIMMs in slots 1 to 4.[1]

Jumper board

[edit | edit source]
  • 1 MB to 2.5 MB: remove the two 256K SIMMs from slots 3 and 4, fit two 1 MB SIMMs there, and remove the jumper permanently.[1]
  • 1 MB to 4 MB: remove all four 256K SIMMs, fit four 1 MB SIMMs, remove the jumper permanently.[1]
  • 2 MB to 2.5 MB: fit two 256K SIMMs in slots 1 and 2 and remove the jumper permanently.[1]
  • 2 MB to 4 MB: fit two 1 MB SIMMs in slots 1 and 2 and remove the jumper permanently.[1]

Apple's note: disregard the "2/4 M" label silkscreened on the board. A 4 MB upgrade requires the jumper to be removed.[1]

Macintosh SE, resistor-type logic board
Macintosh SE, jumper-type logic board

Tools

[edit | edit source]
  • T15 Torx screwdriver (long shaft)
  • Case separator or plastic spudger
  • Anti-static wriststrap
  • Matching 30-pin SIMMs

See Recommended Tools.

Procedure

[edit | edit source]

1. Prepare. Power off, unplug, work on a grounded surface.

2. Open the case. The machine contains a CRT: read CRT Discharge Procedure, discharge the CRT to the ground lug before disconnecting anything, and do not fit a grounding wriststrap until after it has been discharged. Apple warns that failing to discharge first can damage the logic board or the analogue board.[1]

3. Withdraw the logic board from the bottom of the chassis to reach the sockets.

4. Remove the existing SIMMs. The retaining clips snap easily; ease them outward gently.

5. Fit the new SIMMs with the notch matched to the socket keying, filling complete rows.

6. Set the resistor or jumper for the new configuration before reassembly.

7. Reassemble and verify the memory figure at startup.

Common problems

[edit | edit source]
Symptom Likely cause Action
Sad Mac, or a chime followed by nothing Wrong, faulty or partly seated SIMMs 30-pin, 150 ns or faster, eight-chip, non-parity, fully seated
Sad Mac with the memory jumper suspected Configuration not set Apple's own chart says to verify the three-pin jumper is configured correctly before replacing anything[1]
Memory figure unchanged Resistor still fitted, or jumper still installed Clip R35/R36, or remove the jumper, as above
Half the expected memory A row is half-populated, or the larger pair is in the wrong row Fill rows completely and observe the row rule for your board type

Sad Mac codes are decoded on Sad Mac Error Codes and with the Sad Mac Decoder. Apple's chart also points at individual SIMMs for particular codes.[1]

[edit | edit source]

References

[edit | edit source]
  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 1.14 1.15 Apple Computer, Macintosh SE Service Source — Specifications (Memory) and Upgrades (Memory Upgrade) chapters. Hosted on this wiki: File:Macintosh se.pdf.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Apple Computer, Guide to the Macintosh Family Hardware, 2nd edition, Addison-Wesley, 1990, Chapter 5 "Memory", pp. 196–198 — SIMM rules, RAM SIZE resistors and the later jumper for the Macintosh SE.
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