Macintosh IIx

Macintosh IIx

Macintosh IIx
Specifications
Manufacturer	Apple Computer, Inc.
Type	Desktop personal computer
Released	19 September 1988
Discontinued	15 October 1990
Intro price	US$7,800 / US$9,300 at introduction
CPU	Motorola 68030 at 15.6672 MHz (marketed as 16 MHz)
Memory	1 MB or 4 MB standard; Apple specifies expandable to 8 MB, 128 MB achievable with 16 MB SIMMs and 32-bit addressing
Storage	Optional internal 40 MB or 80 MB SCSI hard drive
Display	—
Sound	Apple custom sound chip, 8-bit stereo sampling at 44.1 kHz, four-voice wavetable synthesis
Graphics	None built in — requires a NuBus video card
ROM	256 KB, "32-bit dirty"
FPU / coprocessor	Motorola 68882
Media	Internal 1.4 MB SuperDrive; optional second internal drive
Ports / interface	Two ADB, two RS-232/RS-422 mini DIN-8 serial, DB-25 SCSI, DB-19 floppy
Expansion	Six NuBus slots, one processor-direct slot
Power	100–240 VAC auto-configuring, 48–62 Hz, 220 W maximum
Dimensions	5.5 × 18.7 × 14.4 in (14.0 × 47.4 × 36.5 cm)
Weight	24 lb (10.9 kg)
OS / Firmware	System 6.0.2 onwards
Predecessor	Macintosh II
Successor	Macintosh IIfx
Codename	Spock, Stratos
Model no.	M5840 (order no. M5280); Gestalt ID 7

The Macintosh IIx was introduced on 19 September 1988 as an incremental revision of the Macintosh II. It kept the six-slot NuBus chassis and swapped the 68020 for a 68030 at the same clock, added a 68882 as standard and fitted the 1.4 MB SuperDrive — the first Macintosh II to ship with one.

Everything on this page that is a number comes from Apple's own Service Source for the Macintosh II, IIx and IIfx, hosted on this wiki, or from a named community source that says where it got it.

Specification

Apple's specification

Item	Figure
Processor	Motorola 68030 with built-in paged memory management unit
Coprocessor	Motorola 68882
Addressing	32-bit registers, 32-bit address bus, 32-bit data bus
RAM	1 MB, expandable to 8 MB (Apple's figure — see below)
ROM	256 K
Floppy	Internal 1.4 MB drive; optional second internal 1.4 MB drive
Hard drive	Optional internal 40, 80 or 160 MB
SCSI	5 MB/s transfer rate, eight devices maximum
ADB	Two ports, daisy-chainable
Serial	Two RS-232/RS-422, mini DIN-8
NuBus	Six internal slots, full 32-bit address and data buses
Sound	Apple custom digital sound chip: 8-bit stereo sampling at 44.1 kHz, four-voice wavetable synthesis, drives stereo headphones through the sound jack
Line voltage	100–240 VAC, automatically configured
Frequency	48–62 Hz, single phase
Maximum power	220 W, monitor excluded
Dimensions	5.5 × 18.7 × 14.4 in (14.0 × 47.4 × 36.5 cm)
Weight	24 lb (10.9 kg), more with an internal hard drive

All of that is Apple's. Three corrections to figures that circulate widely:

• 220 W, not 230 W. Apple gives 220 W for the II and IIx and 230 W for the IIfx. The two get swapped.
• The supply is auto-configuring, not switch-selectable. Apple specifies 100–240 VAC "automatically configured". There is no voltage selector switch to set wrongly.
• The model number is M5840, order number M5280 for the 1 MB configuration; Gestalt ID 7.

Memory

Apple's published ceiling is 8 MB — eight 30-pin SIMM sockets in two banks of four, filled in groups of four, 120 ns or faster. In practice the machine addresses much more: with 16 MB SIMMs in all eight sockets, 32-bit addressing and the MODE32 extension, a IIx will run 128 MB.

The reason Apple's number is lower is the ROM. The IIx's 256 K ROM is "32-bit dirty" — it contains 24-bit addressing code — which caps usable memory at 8 MB unless MODE32 or the 32-Bit System Enabler patches it. This is a software limit with a software fix, not a hardware fault, and a IIx that reports 8 MB with more fitted is behaving exactly as documented.

Apple also names a specific memory fault on this family: Apple-labelled SIMMs manufactured by NEC with a date code of 9052 or below are the first thing its symptom charts tell a technician to replace for an error chord at startup, for a system that will not boot, for video ghosting and for a system that boots and then loses video. Four separate symptoms, one part. If you have unknown-provenance Apple SIMMs in a machine doing any of those things, read the date codes.

A note on the clock figure

Apple prints two different numbers for the same design. The Macintosh II/IIx/IIfx Service Source gives the II and IIx as 15.6772 MHz; the Macintosh IIcx/IIci/Quadra 700 Service Source gives the IIcx — the same 16 MHz-class design — as 15.6672 MHz. The second is the one to believe: the boards carry a 31.3344 MHz crystal, which is exactly twice 15.6672 MHz, and it is legible in Recap-a-Mac's photograph of the IIcx board. "16 MHz" is the marketing figure and what EveryMac and Apple's own sales material use.

Power

Power supply Apple part 661-0375, shared with the Macintosh II; the IIfx uses 661-0542. Logic board 661-0529 (661-0528 for the II, 661-0522 for the IIfx). Bottom cover 630-5494 distinguishes a IIx from a II (630-5227) and a IIfx (630-5806).

What Apple does and does not publish

Apple publishes no rail tolerance and no power-supply adjustment procedure for the Macintosh II, IIx or IIfx. The Service Source contains no acceptable-range table for any rail and no trimmer adjustment; every power fault in the symptom charts ends in "Replace power supply". The "+5 V 4.85–5.15 V / +12 V 11.9–12.7 V" table that circulates on pages of this era is Apple's Macintosh Plus procedure — genuine there, where it uses voltage test cable 077-0135 on the external floppy port — copied onto machines it was never written for. Neither it nor any invented substitute appears on this page.

Apple does give one rail check, in the hard-disk symptom chart: if an internal drive will not spin and its LED does not light, verify the +5 V and +12 V lines to the drive before replacing anything. That is a presence test, not a tolerance test, and it is the only rail measurement Apple asks for.

Recapping the supply

You may open it, and on a machine this age you probably should. Understand what is live in it first: it is mains-rectified, so with the cover off and the lead plugged in the fuse, input filter, bridge rectifier and reservoir capacitors sit at mains potential and hold a charge after the plug comes out. Unplug, discharge each large reservoir through a 1 kΩ / 5 W resistor, and confirm with a meter that it reads near zero before a tool goes near the primary side. If your unit has two reservoir capacitors in series across the rectified mains, replace both together with matched parts — a single capacitor in place of the pair will fail on European mains, violently.

Battery

This machine has two lithium cells, not one. Apple's battery verification and replacement procedures for the II, IIx and IIfx are written in the plural throughout, and the illustration shows a pair of holders side by side; the symptom charts say "check batteries". Recap-a-Mac's board photograph shows both holders.

• Set a meter to the 10 V DC range.
• Positive probe on the end of the cell marked "+" on the logic board, negative probe on the other end.
• Replace the battery if it reads below 3.2 V.

3.2 V is this machine's figure. It is not the 2.8 V of the IIcx, IIci and Quadra 700, nor the 3.0 V of the IIsi and the LC series. Apple's thresholds are machine-specific and get transplanted between pages; use the one printed in your own machine's manual.

Apple's removal is simple: prise the latch away from the holder with a small flat-blade screwdriver, lift the cover off and lift the cell out.

Machines with no battery holder

Early Macintosh II and IIx boards have their cells soldered directly to the logic board. Apple's own instruction is unambiguous: before you change the batteries in a Macintosh II or IIx that has no battery holder, fit the battery holder board first.

Apple's cautions on that job are worth repeating because both are easy to get wrong:

• Do not force the old connections free — you will pull the copper off the board. Remove the wire from each hole and clear the hole of solder instead.
• The holder board is polarised. Apple marks the positive holes on the logic board, and putting the holder in the wrong way round may damage the board.

If your machine still has soldered cells, this is the single most valuable preventive job you can do to it. A soldered cell cannot be removed for storage, and a soldered cell that leaks takes the traces underneath it with it.

If it has leaked

These are lithium cells, so neutralise with bicarbonate of soda, not vinegar. Vinegar is the right treatment for alkaline leakage; it is the wrong treatment here and it adds water and chloride to an already corroded board. Bicarbonate paste in distilled water, rinse with distilled water, follow with isopropyl alcohol, dry thoroughly — then buzz out every track running away from the holders, and check the underside of the board. See Battery Explosion, Capacitor or Corrosion Damage and Battery Refurbishment.

Take the cells out before the machine goes into storage.

Capacitors

Logic board 820-0229-A. Twenty electrolytics:

Macintosh IIx logic board 820-0229-A

Value	Working voltage	Quantity	Package
47 µF	16 V	15	Surface-mount
470 µF	16 V	3	Axial
220 µF	16 V	1	Axial
10 µF	16 V	1	Axial, with surface-mount pads also present

Two independent community sources give exactly that complement — MacDat's reference list and Recap-a-Mac's annotated photograph of an 820-0229-A board, which is hosted here as File:Mac IIx Recap Guide.jpg. Console5's per-designator list for the same board agrees value for value.

Macintosh IIx logic board 820-0229-A with every electrolytic marked with its value, working voltage and positive terminal. The two battery holders are visible above centre. Source: Recap-a-Mac.

Apple published no component-level capacitor data for any Macintosh of this era, so all three sources are readings of physical boards rather than manufacturer specifications. They agree, which is about as good as corroboration gets. Read the value off each can before you lift it.

The four axial parts are the ones people miss. They do not look like the surface-mount cans and they sit apart from them, but they are electrolytic and they age the same way. The 10 µF position has surface-mount pads underneath it, so it can be rebuilt either way.

What failure looks like: audio faults first, then intermittent starting, then visible residue — brown or amber staining around a base, dull solder mask nearby, green or white crystalline deposits where electrolyte has reached copper. A small surface-mount electrolytic does not have to look swollen to have failed; the usual failure is a seeped seal and the evidence hides under the can. See Capacitor Failure Symptoms.

Connectors and sockets

Oxidised contacts cause more intermittent faults on a machine this age than failed silicon does, and they are the cheapest thing to put right.

• SIMM sockets. Clean with isopropyl alcohol on a swab and reseat. Do not take an abrasive to a module's gold fingers — once you are through the plating, the base metal oxidises and then transfers to every socket the module touches.
• VRAM sockets. Same treatment. Video faults that come and go when the case is knocked usually start here.
• NuBus and PDS slots. Inspect for bent contacts and debris before a card goes home; check the card's edge fingers too.
• ROM SIMM socket, where one is fitted. A poorly seated ROM gives a machine that chimes and does nothing else.
• Logic-board power connector. Look for browning or a distorted housing. A discoloured power connector is a warning, not a cosmetic problem.
• ADB, serial, SCSI and floppy connectors. Reseat; check ribbon cables for cracked conductors where they fold.

A contact cleaner such as DeoxIT D5 earns its place on genuinely corroded contacts. It is not a preventive treatment and it does not belong on clean gold.

Cleaning

Opening the case

Release the catches at the rear and slide the top cover forward and off. Apple's take-apart sequence then removes the drive mount before the logic board — and note that battery verification on this machine requires the cover and the drive mount to come out first, which is why it is worth doing while you have the machine open for something else.

Inside

• Compressed air and an anti-static brush on the logic board, the supply and the fan. Hold the fan blade still while you blow it: spinning a fan with compressed air drives it as a generator and puts a reverse voltage back down its cable.
• Isopropyl alcohol (99 %) and a soft brush for grime, working outwards from each capacitor and from the battery holder.
• Check the underside of the board as well as the top. Both battery and capacitor electrolyte travel through vias.

Outside

• A damp microfibre cloth and mild detergent. No abrasives, no solvents — the texture on these shells does not survive either.
• ADB keyboards come apart for washing: keycaps off, warm soapy water, dry them completely, then clean the contacts with isopropyl alcohol.
• Mouse ball out, rollers scraped and wiped with isopropyl alcohol.

The platinum-grey plastics yellow with age. The discolouration is in the body of the plastic rather than on the surface, so cleaning will not shift it; see Retrobrite for what can be done and what it costs in brittleness.

Floppy drive

The 1.4 MB Apple SuperDrive is direct drive. It has no belt. Advice to fit a new belt to a sluggish or non-ejecting SuperDrive — including to the auto-inject version — is wrong: there is nothing there to replace. What these drives actually suffer is hardened grease on the head carriage and eject rails, dust in the mechanism, and dirty or worn heads. On manual-inject drives a worn eject gear is a genuine and common failure.

• Clean the heads with isopropyl alcohol on a lint-free swab, supporting the upper head arm so it is not sprung.
• If the rails are stiff, re-lubricate with a silicone grease — not white lithium grease, which gums up as it ages.
• If a disc will not eject, hold the mouse button down while switching the machine on to run a full eject cycle before taking anything apart.

See Macintosh Floppy Drive Maintenance.

Hard disk

The original SCSI mechanisms are past thirty years old and the usual failures are a stuck spindle, dried head-park grease and dead controller electronics. Solid-state replacements — BlueSCSI, ZuluSCSI, SCSI2SD — are quieter, cooler and considerably more reliable, and they let you keep the original drive on a shelf.

Whatever you fit, get the termination right: the drive at the end of the internal bus must be terminated, and the computer itself is always SCSI ID 7. See Macintosh HDD Maintenance.

Apple's own SCSI notes for this chassis: the external device's ID switch must not be set to 0 (the internal drive) or 7 (the computer), and "drive icon does not appear on the desktop" and "data is lost or corrupted" both resolve to a termination check in Apple's symptom charts.

Things that are not faults

• A system that shuts down intermittently after long use. Apple's first cure is to make sure the air vents on the sides and top are unobstructed, because the thermal protection circuitry may have shut the machine down — and it should be usable again after 30–40 minutes. That is a designed behaviour, not a failure.
• 8 MB reported with more fitted. The ROM is 32-bit dirty; see above.
• An MS-DOS drive refusing a disc formatted on the 1.4 MB drive. Apple's instruction is to format all such discs on the MS-DOS drive first.
• No built-in video. The IIx has none. A NuBus video card is not an upgrade, it is a requirement.

Storage

• Take the battery out.
• Store dry and at room temperature — not a loft, not a garage.
• If the logic board comes out, bag it anti-statically and lay it flat.
• Nothing needs periodic running. "Power it up every few months to keep the capacitors formed" is repeated widely and supported nowhere for machines of this kind. The real hazard to a stored Macintosh is the cell in the battery holder, and removing it costs nothing.

Related pages

• Macintosh II — direct predecessor
• Macintosh IIfx — the fast member of the same chassis
• Macintosh IIcx — the compact three-slot version
• Macintosh IIci — built-in video and a 32-bit clean ROM
• Macintosh II/IIx/IIfx Service Source
• Capacitor Failure Symptoms
• Battery Explosion, Capacitor or Corrosion Damage
• Recommended Tools