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= Macintosh Quadra 840AV =
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Introduction
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The Macintosh Quadra 840AV is a personal computer designed,
manufactured, and sold by Apple Computer from July 1993 to July 1994.
It was introduced alongside the Centris 660AV, where "AV" signifies
audiovisual capabilities, such as video input and output,
telecommunications, speech recognition, and enhanced audio. The 840AV
has the same mini-tower form factor as the Quadra 800, with a faster
Motorola 68040 processor.
The Quadra 840AV was discontinued shortly after the introduction of
the PowerPC-based Power Macintosh. The Power Macintosh 8100/80AV
provides the same functionality in the same form factor, and had a
significantly higher price point. The 7100/66AV was priced comparably
to the 840AV but in a IIvx-style desktop case.
Hardware
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At launch, Quadra 840AV's 40 MHz Motorola 68040 CPU and interleaved
RAM made it the fastest Macintosh available, topping both the
nominally higher-end Quadra 950 and the Quadra 800 by 7 MHz. It
remains both the fastest Quadra and the fastest 68k Macintosh of all
time, because all later high-end Macintoshes are PowerPC-based Power
Macintoshes. The 840AV is the only Mac to use the 40 MHz-clocked
68040. It sports a faster 66.7 MHz AT&T DSP 3210 Digital Signal
Processor chip, compared with the 55 MHz variant in the 660AV. The
on-board DSP was primarily intended to speed up audio/video
processing, although few Mac programs make use of this due to the
complexity of programming it.
The 840AV and its relative, the Centris/Quadra 660AV, marked a number
of firsts for the Macintosh family. They are the first Macintoshes to
include on-board 16-bit 48 kHz stereo audio playback and recording
capability, and S-Video and composite video input and output. To
improve video playback, two separate frame buffers are used: one for
standard graphics, and one specifically for video. This enables the
live video input to be displayed as a scalable "window" within the
Macintosh user interface. They are also the first personal computers
that supported speech recognition (PlainTalk) out-of-the-box. The
Apple GeoPort Telecom Adapter Kit introduced with the AV Macs add many
DSP-based telecommunication functions, such as modem, fax, and
telephony.
The Quadra 840AV has a similar case to the earlier Macintosh Quadra
800; the housing, chassis, power supply, and internal storage
assemblies are the same, but the front and rear panels changed, with
the power button being moved to the front.
Internally, the 840AV is significantly different. Apart from the
faster processor, the logic board lacks the 800's Processor Direct
Slot and second ADB port, but has a DAV slot (in line with NuBus slot
A) and the new GeoPort. Also, unlike the 800's 8 MB of fixed RAM, all
of the 840AV's memory is in SIMMs (this is the reason why the maximum
amount of memory is lower).
The way in which the 840AV deals with its memory (DRAM) differs from
the other machines of its generation (Quadra 700, 800, 950) in that 4,
8, 16, or 32 MB 72-pin 60ns SIMMs may be installed up to 128 MB and
sizes can be mixed. However, the Quadra 840AV does not support 1 MB, 2
MB, or 64 MB SIMMs. The 840AV and 660AV are the first Macintosh
computers to operate in 32-bit mode at all times, and cannot be
toggled back to 24-bit mode, which may be useful for using early Nubus
cards that conform to the 24-bit addressing.
Notable uses
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The Quadra 840AV was part of a hardware package that was offered with
the initial release of Media 100.
Reception
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Jonathan Chevreau of the 'National Post' said on August 7, 1993 that
the Quadra 840AV and Centris 660AV were the next most interesting
multimedia computers behind the new SGI Indy, putting Apple among the
forefront of the birth of the major industry of desktop multimedia.
Ben Thompson of 'Byte' magazine said in September 1993 that Apple and
Silicon Graphics were trailblazers by setting audio and video input as
default features of those two Macintosh and of the Indy desktop PCs,
which "could change the way businesspeople communicate". He said the
new AV Macs had a surprising leap in features, breaking Apple's trend
of slow but stable incremental technology refreshes. He tested the
840AV as the overall fastest Macintosh, attributing this to its
"radically" new AV series hardware features such as dedicated DMA
channels for SCSI, serial, ethernet, and soundbut noted that the SCSI
DMA performance is completely lost on the legacy architecture of
System 7 pending a complete microkernel-based rewrite of the operating
system such as with Pink or Copland. He tested the wealth of AV
features such as telecommunications, print-to-fax, speech recognition,
and video capture, and appreciated their productivity gains with
surprisingly no compatibility problems.
External links
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* [https://support.apple.com/kb/SP237 Macintosh Quadra 840AV:
Technical Specifications] at Apple Support
* [http://apple-history.com/?page=gallery&model=840 Quadra 840AV]
at apple-history.com
* [http://lowendmac.com/1993/quadra-840av/ Quadra 840AV profile] at
Low End Mac
*
[http://www.everymac.com/systems/apple/mac_quadra/stats/mac_quadra_840av.html
Quadra 840AV] at EveryMac.com
License
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Original Article: http://en.wikipedia.org/wiki/Macintosh_Quadra_840AV