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Rebuilt against Apple Macintosh 128K/512K Service Source: DELETED fabricated memory map, ROM module layout, video timing table, sound path (LM380/MC6883 PAL), HN462716 ROM claim and the startup-chime easter egg; specifications now Apple-sourced (64KB ROM, 60W, DE-9 serial, RJ-11 keyboard); release_date parameter fixed; real 26LS30/CR18 faults from Dead Mac Scrolls; refs and reflist
 
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| manufacturer = Apple Computer, Inc.
| manufacturer = Apple Computer, Inc.
| type        = Personal computer
| type        = Personal computer
| release_date = September 10, 1984
| release_date = September 1984
| discontinued = April 14, 1986
| discontinued = April 1986
| price        = US$3,195
| price        = US$3,195
| cpu          = Motorola 68000 @ 7.83 MHz
| cpu          = Motorola 68000 @ 7.83 MHz
| memory      = 512 KB RAM (not expandable)
| memory      = 512 KB, soldered, not user-expandable
| storage      = 400 KB 3.5″ floppy drive
| rom          = 64 KB
| display      = 9″ monochrome CRT (512 × 342 px)
| storage      = Internal single-sided 400 KB 3.5-inch floppy drive
| sound        = Monaural 8‑bit, 22 kHz (4‑voice)
| display      = 9-inch monochrome CRT, 512 × 342 pixels
| dimensions  = 13.6″ H × 9.6″ W × 10.9″ D
| sound        = Four-voice, 8-bit D/A conversion, 22 kHz sampling
| weight      = 16.5 lb (7.5 kg)
| ports        = DB-19 external floppy; DE-9 mouse; RJ-11 keyboard; 2 × RS-232/RS-422 serial (DE-9)
| os          = System 1.0 – System 4.1
| power        = 105–125 V AC, 50–60 Hz, 60 W maximum
| predecessor  = [[Macintosh 128K]]
| dimensions  = 13.6 in H × 9.6 in W × 10.9 in D (34.5 × 24.4 × 27.6 cm)
| successor    = [[Macintosh 512Ke]]
| weight      = 16 lb 8 oz (7.5 kg)
| codename    = Engine, Hero
| os          = System 1.1 – System 4.1
| predecessor  = [[Macintosh 128K]]
| successor    = [[Macintosh 512Ke]]
| codename    = Fat Mac
| model        = M0001W
| model        = M0001W
}}The '''Macintosh 512K''', released on '''September 10, 1984''', was an improved version of the [[Macintosh 128K]]. It featured '''four times the RAM (512 KB)''', allowing for improved multitasking and compatibility with a wider range of software. It retained the same '''Motorola 68000 processor running at 7.83 MHz''' and the '''9-inch monochrome display''' with a '''400 KB floppy disk drive'''.
}}
The '''Macintosh 512K''' was introduced in September 1984 as a [[Macintosh 128K]] with four times the memory. Everything else — the 68000 processor, the 64 KB ROM, the 9-inch monochrome screen and the single-sided 400 KB floppy drive — is the same, and Apple services the two machines from a single manual.<ref name="ss128">Apple Computer, ''Macintosh 128K/512K Service Source'' — Specifications, Take Apart and Adjustments chapters. Hosted on this wiki: [[:File:Macintosh 128k.512k.pdf]].</ref> It sold for US$3,195 and was nicknamed the Fat Mac.<ref name="ah">apple-history.com, ''Macintosh 512K'' (secondary source, used for the introduction price, codename and market dates).</ref>


Due to its increased memory, the Macintosh 512K could run more advanced applications, including '''MacDraw''', '''MacProject''', and '''Microsoft Multiplan'''. However, it still lacked built-in support for an internal hard drive, relying on external floppy drives for additional storage. The 512K model was succeeded by the [[Macintosh Plus]], which introduced '''expandable RAM and an external SCSI port'''.
The extra memory made the machine usable with the larger applications of the period, but it still had no internal hard disk, no SCSI port and no memory expansion: the RAM is soldered down. The [[Macintosh Plus]] addressed all three.


== Maintenance ==
== Maintenance ==
Due to the 512K's similarities with the 128K, there is no difference in it's maintenance, PCB or Schmatics, please see the [[Macintosh 128K]] page for maintenance, guides and more information.
 
The 512K is mechanically and electrically the same machine as the 128K, so its servicing, board layout and schematics are shared. See '''[[Macintosh 128K/512K General Maintenance]]''' and the [[Macintosh 128K]] page.
 
The machine contains a CRT; read [[CRT Discharge Procedure]] before opening the case.
 
== Specifications ==
 
Every figure in this table is from Apple's own specification pages for the 128K/512K.<ref name="ss128" />
 
<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:80%;"
! Item !! Specification
|-
| CPU || Motorola 68000, 7.83 MHz
|-
| RAM || 512 KB (the same manual covers the 128 KB machine)
|-
| ROM || 64 KB
|-
| PRAM || CMOS custom chip with 256 bytes of parameter memory, backed by a 4.5 V user-replaceable battery
|-
| Floppy drive || Internal single-sided 3.5-inch drive, 400 KB
|-
| External floppy || DB-19 connector
|-
| Mouse || DE-9 connector; mechanical tracking, optical shaft encoding at 3.54 pulses per mm
|-
| Keyboard || 58 keys, software mapped, RJ-11 connector
|-
| Serial || Two RS-232/RS-422 ports, DE-9 connectors
|-
| Sound || Four-voice, 8-bit digital/analogue conversion, 22 kHz sampling rate
|-
| Video || 9-inch diagonal screen, 512 × 342 bit-mapped display
|-
| Line voltage || 105–125 V AC, 50–60 Hz
|-
| Maximum power || 60 W
|-
| Dimensions || 13.6 × 9.6 × 10.9 in (34.5 × 24.4 × 27.6 cm)
|-
| Weight || 16 lb 8 oz (7.5 kg)
|}
 
== Memory ==
 
The 512 KB is soldered to the logic board. Apple offered no memory upgrade for this machine, and the RAM configuration is fixed in the logic that decodes it; period third-party boards that fitted Macintosh Plus ROMs and more memory existed, but they are logic board modifications rather than upgrades.<ref name="ah" /> The Macintosh Plus, which introduced the four 30-pin SIMM sockets used across the rest of the compact family, is documented on the [[Macintosh Plus Memory Upgrade Guide]].
 
== Power rails ==
 
Unlike the later compacts, this generation '''does''' have a published voltage adjustment. Apple's procedure connects the Macintosh voltage test cable (part number 077-0135) to the external floppy port and adjusts the regulator on the power/sweep board for '''11.90–12.75 V''' on the orange lead and '''4.85–5.15 V''' on the red lead; if both cannot be brought inside those windows the board is replaced.<ref name="ss128" /> The full procedure, with its warnings, is written up on [[Macintosh Plus General Maintenance]], which uses the same board family.
 
== Known board-level faults ==
 
''The Dead Mac Scrolls'' documents two faults that present as software problems:<ref name="dms">Larry Pina, ''The Dead Mac Scrolls'', Peachpit Press, 1992, "Early Macs" chapter. Hosted on this wiki: [[:File:The Dead Mac Scrolls 1992.pdf]].</ref>
* A 512K or 512Ke that resets a directly connected ImageWriter II on the printer port, or that never appears on an AppleTalk network, usually has a failed '''26LS30''' line driver at board location '''B6'''.
* On an original 128K analogue board that has been paired with an upgraded logic board, repeatable system errors that no other Macintosh shows are a low +5 V rail; the overvoltage reference diode (1N5349B) at '''CR18''' is the part to check.
 
== Related pages ==
* [[Macintosh 128K]]
* [[Macintosh 512Ke]]
* [[Macintosh Plus]]
* [[Macintosh 128K/512K General Maintenance]]
* [[Sad Mac Error Codes]] and the [[Sad Mac Decoder]]
* [[CRT Discharge Procedure]]
 
== References ==
<references />


[[Category:Apple Vintage Computers]]
[[Category:Apple Vintage Computers]]


{{Navbox-AppleVintage}}
{{Navbox-AppleVintage|state=collapsed}}

Latest revision as of 18:16, 23 September 2026

Macintosh 512K
Specifications
ManufacturerApple Computer, Inc.
TypePersonal computer
ReleasedSeptember 1984
DiscontinuedApril 1986
Intro priceUS$3,195
CPUMotorola 68000 @ 7.83 MHz
Memory512 KB, soldered, not user-expandable
StorageInternal single-sided 400 KB 3.5-inch floppy drive
Display9-inch monochrome CRT, 512 × 342 pixels
SoundFour-voice, 8-bit D/A conversion, 22 kHz sampling
ROM64 KB
Ports / interfaceDB-19 external floppy; DE-9 mouse; RJ-11 keyboard; 2 × RS-232/RS-422 serial (DE-9)
Power105–125 V AC, 50–60 Hz, 60 W maximum
Dimensions13.6 in H × 9.6 in W × 10.9 in D (34.5 × 24.4 × 27.6 cm)
Weight16 lb 8 oz (7.5 kg)
OS / FirmwareSystem 1.1 – System 4.1
PredecessorMacintosh 128K
SuccessorMacintosh 512Ke
CodenameFat Mac
Model no.M0001W

The Macintosh 512K was introduced in September 1984 as a Macintosh 128K with four times the memory. Everything else — the 68000 processor, the 64 KB ROM, the 9-inch monochrome screen and the single-sided 400 KB floppy drive — is the same, and Apple services the two machines from a single manual.[1] It sold for US$3,195 and was nicknamed the Fat Mac.[2]

The extra memory made the machine usable with the larger applications of the period, but it still had no internal hard disk, no SCSI port and no memory expansion: the RAM is soldered down. The Macintosh Plus addressed all three.

Maintenance

[edit | edit source]

The 512K is mechanically and electrically the same machine as the 128K, so its servicing, board layout and schematics are shared. See Macintosh 128K/512K General Maintenance and the Macintosh 128K page.

The machine contains a CRT; read CRT Discharge Procedure before opening the case.

Specifications

[edit | edit source]

Every figure in this table is from Apple's own specification pages for the 128K/512K.[1]

Item Specification
CPU Motorola 68000, 7.83 MHz
RAM 512 KB (the same manual covers the 128 KB machine)
ROM 64 KB
PRAM CMOS custom chip with 256 bytes of parameter memory, backed by a 4.5 V user-replaceable battery
Floppy drive Internal single-sided 3.5-inch drive, 400 KB
External floppy DB-19 connector
Mouse DE-9 connector; mechanical tracking, optical shaft encoding at 3.54 pulses per mm
Keyboard 58 keys, software mapped, RJ-11 connector
Serial Two RS-232/RS-422 ports, DE-9 connectors
Sound Four-voice, 8-bit digital/analogue conversion, 22 kHz sampling rate
Video 9-inch diagonal screen, 512 × 342 bit-mapped display
Line voltage 105–125 V AC, 50–60 Hz
Maximum power 60 W
Dimensions 13.6 × 9.6 × 10.9 in (34.5 × 24.4 × 27.6 cm)
Weight 16 lb 8 oz (7.5 kg)

Memory

[edit | edit source]

The 512 KB is soldered to the logic board. Apple offered no memory upgrade for this machine, and the RAM configuration is fixed in the logic that decodes it; period third-party boards that fitted Macintosh Plus ROMs and more memory existed, but they are logic board modifications rather than upgrades.[2] The Macintosh Plus, which introduced the four 30-pin SIMM sockets used across the rest of the compact family, is documented on the Macintosh Plus Memory Upgrade Guide.

Power rails

[edit | edit source]

Unlike the later compacts, this generation does have a published voltage adjustment. Apple's procedure connects the Macintosh voltage test cable (part number 077-0135) to the external floppy port and adjusts the regulator on the power/sweep board for 11.90–12.75 V on the orange lead and 4.85–5.15 V on the red lead; if both cannot be brought inside those windows the board is replaced.[1] The full procedure, with its warnings, is written up on Macintosh Plus General Maintenance, which uses the same board family.

Known board-level faults

[edit | edit source]

The Dead Mac Scrolls documents two faults that present as software problems:[3]

  • A 512K or 512Ke that resets a directly connected ImageWriter II on the printer port, or that never appears on an AppleTalk network, usually has a failed 26LS30 line driver at board location B6.
  • On an original 128K analogue board that has been paired with an upgraded logic board, repeatable system errors that no other Macintosh shows are a low +5 V rail; the overvoltage reference diode (1N5349B) at CR18 is the part to check.
[edit | edit source]

References

[edit | edit source]
  1. ↑ 1.0 1.1 1.2 Apple Computer, Macintosh 128K/512K Service Source — Specifications, Take Apart and Adjustments chapters. Hosted on this wiki: File:Macintosh 128k.512k.pdf.
  2. ↑ 2.0 2.1 apple-history.com, Macintosh 512K (secondary source, used for the introduction price, codename and market dates).
  3. ↑ Larry Pina, The Dead Mac Scrolls, Peachpit Press, 1992, "Early Macs" chapter. Hosted on this wiki: File:The Dead Mac Scrolls 1992.pdf.


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