Editing Macintosh Quadra 840AV

{{Infobox computer
| name         = Macintosh Quadra 840AV
| image        = [[File:Apple_mac_quadra_800.jpg|250px]]
| caption      = Macintosh Quadra 840AV
| manufacturer = Apple Computer, Inc.
| type         = Personal Computer
| release date = July 29, 1993
| discontinued = July 18, 1994
| price        = US$3,500 – US$5,100
| cpu          = Motorola 68040 @ 40 MHz
| memory       = 8 MB RAM (expandable to 128 MB)
| storage      = 230 MB / 500 MB / 1 GB SCSI HDD, 1.44 MB floppy, optional 2X CD-ROM
| display      = 512×384 to 1152×870, 1 MB VRAM (expandable to 2 MB)
| sound        = 16-bit stereo, 48 kHz; AT&T DSP 3210 @ 66.7 MHz
| dimensions   = 14.0" H × 7.7" W × 15.75" D (35.6 × 19.6 × 40 cm)
| weight       = 25.3 lbs (11.5 kg)
| os           = System 7.1 – Mac OS 8.1
| predecessor  = [[Macintosh Quadra 800|Quadra 800]]
| successor    = [[Power Macintosh 8100|Power Macintosh 8100/80AV]]
| codename     = Cyclone
| model        = M9020
}}
The '''Macintosh Quadra 840AV''' is a personal computer designed, manufactured, and sold by Apple Computer from July 1993 to July 1994.<ref>{{cite web |url=https://everymac.com/systems/apple/mac_quadra/specs/mac_quadra_840av.html |title=Macintosh Quadra 840AV Specs |publisher=EveryMac.com |access-date=2026-02-10}}</ref> It was introduced alongside the [[Macintosh Quadra 660AV|Quadra 660AV]], where "AV" signifies audiovisual capabilities including video input and output, telecommunications, speech recognition, and enhanced audio. The 840AV uses the same mini-tower case as the [[Macintosh Quadra 800|Quadra 800]], with a significantly different logic board featuring a faster Motorola 68040 processor.

The Quadra 840AV holds the distinction of being the fastest 68K-based Macintosh ever produced. Its 40 MHz 68040 processor makes it faster than both the [[Macintosh Quadra 950|Quadra 950]] and [[Macintosh Quadra 800|Quadra 800]], and no faster 68K Macintosh was released before Apple transitioned to the PowerPC architecture.<ref>{{cite web |url=https://en.wikipedia.org/wiki/Macintosh_Quadra_840AV |title=Macintosh Quadra 840AV |publisher=Wikipedia |access-date=2026-02-10}}</ref>

== Architecture and Processor ==

The Quadra 840AV features a Motorola 68040 processor running at 40 MHz with an integrated FPU. The processor has a 32-bit data path and 32-bit address bus, operating in 32-bit mode at all times—it cannot be toggled to 24-bit mode, unlike earlier Quadra models.<ref>{{cite web |url=https://everymac.com/systems/apple/mac_quadra/specs/mac_quadra_840av.html |title=Macintosh Quadra 840AV Specs |publisher=EveryMac.com |access-date=2026-02-10}}</ref>

The system bus runs at 40 MHz. The processor includes 8 KB of L1 cache. The logic board has 2 MB of ROM.

=== AT&T DSP 3210 Digital Signal Processor ===

The 840AV includes an AT&T DSP 3210 digital signal processor running at 66.7 MHz (faster than the 55 MHz variant in the 660AV). This DSP was intended to accelerate audio and video processing tasks, though relatively few Mac applications made use of it due to the complexity of programming the chip directly.

== Memory and Storage ==

=== RAM Configuration ===

The Quadra 840AV has four 72-pin SIMM slots accepting 60 ns RAM. Unlike earlier Quadra models with soldered RAM, all memory in the 840AV is in SIMMs.

<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:70%; text-align:center;"
|+ '''RAM Specifications'''
|-
! Specification !! Value
|-
| Standard RAM || 8 MB or 16 MB
|-
| Maximum RAM || 128 MB
|-
| RAM Type || 72-pin SIMM
|-
| RAM Speed || 60 ns
|-
| SIMM Slots || 4
|-
| Supported SIMM Sizes || 4 MB, 8 MB, 16 MB, 32 MB
|-
| Unsupported SIMM Sizes || 1 MB, 2 MB, 64 MB
|}

The 840AV supports interleaved memory access, which contributed to its performance advantage over other Quadra models.

=== Storage Systems ===

The Quadra 840AV shipped with internal SCSI hard drives in three configurations:
* 230 MB
* 500 MB
* 1 GB

A 1.44 MB 3.5" floppy drive is standard. An internal 2X CD-ROM drive was optional on entry-level configurations and standard on higher-end models. One 5.25" expansion bay is available (or two if no CD-ROM is installed).

== Display and Graphics ==

The Quadra 840AV includes 1 MB of VRAM soldered to the logic board, with four VRAM SIMM slots that can accept 256 KB VRAM SIMMs for a total of 2 MB.

<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:90%; text-align:center;"
|+ '''Display Resolution Support'''
|-
! Resolution !! 1 MB VRAM !! 2 MB VRAM
|-
| 512×384 || 24-bit || 24-bit
|-
| 640×400 || 24-bit || 24-bit
|-
| 640×480 || 16-bit || 24-bit
|-
| 800×600 || 16-bit || 24-bit
|-
| 832×624 || 16-bit || 16-bit
|-
| 1024×768 || 8-bit || 16-bit
|-
| 1152×870 || 8-bit || 16-bit
|}

The 840AV uses two separate frame buffers: one for standard graphics and one specifically for video. This allows live video input to be displayed as a scalable window within the Mac interface.

== Audio Capabilities ==

The Quadra 840AV was the first Macintosh to include on-board 16-bit 48 kHz stereo audio playback and recording capability.<ref>{{cite web |url=https://en.wikipedia.org/wiki/Macintosh_Quadra_840AV |title=Macintosh Quadra 840AV |publisher=Wikipedia |access-date=2026-02-10}}</ref>

Features include:
* 16-bit stereo input and output
* 48 kHz sample rate
* DSP-accelerated audio processing via AT&T DSP 3210
* PlainTalk speech recognition (first Mac to support this out-of-the-box)

== Input/Output and Expansion ==

=== Video I/O ===

The 840AV includes built-in video input and output capabilities:
* S-Video input
* S-Video output
* Composite video input (RCA)
* Composite video output (RCA)

=== Port Configuration ===

* ADB (Apple Desktop Bus) – 1 port (the 800 had two)
* Serial – 2 GeoPort-compatible serial ports (printer and modem)
* SCSI – External SCSI connector
* Ethernet – AAUI-15
* Audio – Stereo input and output

=== GeoPort ===

The two serial ports on the 840AV are GeoPort-compatible. With the Apple GeoPort Telecom Adapter Kit, the DSP can provide modem, fax, and telephony functions via software.

=== Expansion Slots ===

<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:60%; text-align:center;"
|+ '''Expansion Options'''
|-
! Slot Type !! Quantity !! Notes
|-
| NuBus || 3 || Standard NuBus cards
|-
| DAV || 1 || In line with NuBus slot A; for Digital Audio/Video cards
|}

Unlike the [[Macintosh Quadra 800|Quadra 800]], the 840AV does not have a Processor Direct Slot (PDS).

== Model Configurations ==

<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''Quadra 840AV Configurations'''
|-
! Order Number !! RAM !! Hard Drive !! CD-ROM !! Price (1993)
|-
| M9025LL/A || 8 MB || 230 MB || No || US$3,500
|-
| M9028LL/A || 8 MB || 230 MB || 2X || —
|-
| M1836LL/A || 16 MB || 500 MB || No || —
|-
| M1837LL/A || 16 MB || 500 MB || 2X || —
|-
| M1838LL/A || 16 MB || 1 GB || 2X || US$5,100
|}

== General Maintenance ==

For detailed maintenance practices including cleaning, PRAM battery management, connector corrosion prevention, and voltage adjustments, refer to the dedicated [[Macintosh Quadra 840AV General Maintenance]] page.

== Capacitor Replacement Guide ==

Detailed capacitor replacement guidelines for the logic board can be found on the [[Macintosh Quadra 840AV Capacitor Replacement Guide]] page.

== Troubleshooting ==

A comprehensive troubleshooting guide addressing no power, no video, intermittent operation, and other common problems is available on the [[Macintosh Quadra 840AV Troubleshooting]] page.

== Technical Details ==

<templatestyles src="Template:StyledTable/styles.css" />

=== System Architecture at a Glance ===
{| class="wikitable styled-table" style="width:90%; text-align:center;"
! Sub-system !! Specification (Macintosh Quadra 840AV, 1993)
|-
| '''CPU''' || Motorola 68040 @ 40 MHz (with FPU)
|-
| '''DSP''' || AT&T DSP 3210 @ 66.7 MHz
|-
| '''Bus width''' || 32-bit data • 32-bit address
|-
| '''System bus''' || 40 MHz
|-
| '''ROM''' || 2 MB
|-
| '''RAM''' || 8–128 MB (72-pin SIMM)
|-
| '''L1 Cache''' || 8 KB
|-
| '''VRAM''' || 1–2 MB
|-
| '''Video''' || 512×384 – 1152×870
|-
| '''Sound''' || 16-bit stereo, 48 kHz DAC/ADC
|-
| '''Disks''' || 1.44 MB floppy, SCSI HDD, optional CD-ROM
|-
| '''Networking''' || AAUI-15 Ethernet
|-
| '''Ports''' || ADB, SCSI, 2× GeoPort Serial, S-Video I/O, Composite I/O
|}

=== Gestalt ID and Model Numbers ===
{| class="wikitable styled-table" style="width:50%; text-align:center;"
|-
! Identifier !! Value
|-
| Gestalt ID || 78
|-
| Model Number || M9020
|-
| Logic Board || 820-0382
|}

== Service Documentation ==

The official Apple Service Source documentation for this model:

<pdf width="800" height="500">File:Quadra_840av.pdf</pdf>

== See Also ==

* [[Macintosh Quadra 660AV|Quadra 660AV]] – Smaller AV sibling in pizza-box form factor
* [[Macintosh Quadra 800|Quadra 800]] – Shares the same case design
* [[Macintosh Quadra 950|Quadra 950]] – Previous high-end Quadra
* [[Power Macintosh 8100]] – PowerPC successor in the same form factor

== References ==
<references />

[[Category:Apple Vintage Computers]]