Dale Adams on the Fall '93 '040 Macs
Today Apple introduced a number of new desktop machines: the Quadra 605,
Quadra 610, Quadra 650, LC 475, and several Performa variations of the LC
475. As I'm sure many of you are curious about these machines, I thought
I'd post some information on them and try to partially stave off the list
of questions that invariably follows a new product intro.
First, the Q610 and Q650:
The Q610 and Q650 are simply faster versions of their (now discontinued)
Centris counterparts. The Q610 is a 25 MHz version of the C610, and the
Q650 is a 33 MHz version of the C650. This speed increase is the major
change. Most things remain the same, including: I/O support, maximum
memory expansion, number of slots, and video support.
There are a few minor differences. The required speed for VRAM for the
Q610 has increased from 100 ns (for the C610) to 80 ns. Note that the
required speed for DRAM for the Q650 has remained at 80 ns, while the Q800
uses 60 ns DRAM. In addition, there are now more configurations of these
machines which use the 'full' 68040 (i.e., with floating point hardware)
rather than the 68LC040. All versions of the Q650 come with a 68040.
There are versions of the Q610 that come with a 68040, unlike the C610
where all configurations used a 68LC040. A heatsink is not required for a
25 MHz 68040 in the Q610.
From a performance standpoint, the Q610 is about the same speed as the old
C650, and the Q650 is about the same speed as the Q800. The Q610 is
marginally slower than the C650 due to the latter's use of interleaved
memory (a difference of only a few percent). The Q650 is just a tad (one
'tad' being equal to about 3-5 percent) slower than the Q800 due to the
use of 80 ns DRAM in the Q650 instead of the faster 60 ns DRAM used by the
That's about it, really. The best way to look at these products is simply
as faster versions of their old Centris counterparts.
Now, the Q605 and LC475:
The Quadra 605 and LC475 are newly designed machines, although they've
been derived from the earlier member of the Quadra/Centris family. It's
probably more appropriate to look at these two as a single machine, since
the only real differences between them are cosmetic ones. A good way to
visualize these machines is as a Q610 in a smaller box (in the case of the
LC475 the enclosure is identical to that of the LC III), with only a
single DRAM SIMM, no onboard ethernet, and and LC III style expansion slot
instead of a Quadra PDS.
All configurations of these machines come with a 25 MHz 68LC040. Although
there are no versions offered with a 68040, the processor is socketed and
can be removed to allow the use of a 68040. A heat sink is not required
if the processor is upgraded to a 68040. Performance of these machines is
very similar to a Quadra 610 with a 68LC040.
There are 4 MB of DRAM soldered to the logic board. A single 72-pin DRAM
SIMM socket allows memory expansion to 36 MB (using a 32 MB SIMM). SIMM
sizes of 1, 2, 4, 8, 16, and 32 MB are accommodated. Expansion DRAM must
be 80 ns or faster. Only a single SIMM socket is offered due to the lack
of available space on the logic board. (Remember, it's only an LC-sized
The I/O complement of the Q605 and LC475 is basically identical to a Q610
with the exception of no onboard ethernet. One minor difference in the
audio input circuitry is that these machines require the newer PlainTalk
microphone instead of the original Apple microphone used by previous
non-AV '040 Macs.
The onboard video capabilities of these machines are identical to the Q610
(and the Q650, Q800, etc...). All monitors supported by the Q610 are
supported by the Q605 and LC 475, including displays up to a resolution of
1152x870 (i.e., Apple's 21 inch monitor). Video memory can be expanded to
a maximum of 1 MB, and with this amount of VRAM these machines support 16
bits/pixel up to resolutions of 832x624, and 8 bits/pixel at resolutions
Video memory expansion is handled somewhat differently than on the Q610,
however. There is no VRAM soldered to the logic board - all video memory
is on SIMMs. The base amount of VRAM is 512 KB, in the form of two 256 KB
(128K x 16) 80 ns VRAM SIMMs. In order to expand VRAM to 1 MB, the
original SIMMs must be removed and replaced with two 512 KB (256K x 16) 80
ns VRAM SIMMs. Unfortunately, there simply wasn't room on the logic board
for either more SIMM sockets or to solder down the original 512 KB of VRAM.
One other key difference in the onboard video is the lack of sync on the
green video signal. Like the recently introduced AV Macs, the Q605 and
LC475 do not provide a composite sync signal superimposed on the green
The Q605 and LC475 have a single LC-III style expansion slot. It is
compatible with a large number of the expansion cards currently offered
for the LC family. Note that this is not a processor direct slot on these
machines, although it is on earlier LC models. Since the LC slot was
defined as a 68020/68030 PDS, and these new machines have a 68040
processor with a different processor bus, there is a bus adapter necessary
to convert 68040 bus signals to those required by the LC PDS definition.
Because of this, the LC slot does not actually sit directly on the 68040
processor's bus, and hence is not a true PDS.
Basically, what this means to the end user is that not all LC expansion
cards will work (or even make sense, for that matter) in a Q605 or LC475.
In particular, cards such as accelerators, cache cards, and FPU cards
(i.e., 68882's) will not work. However, the majority of I/O related
expansion cards (e.g., video, networking, etc.) should work just fine.
The LC475 comes in the same enclosure as the LC III (with a different
nameplate, of course) and uses the same power supply. It therefore has
the same options for internal drives as that machine. The enclosure for
the Q605 is cosmetically different, but holds the same size logic board,
same power supply, and has the same internal disk drive options as the LC
enclosure. It's my understanding that there will be an upgrade to the
LC475 from the LC II and LC III.
- Dale Adams
November 16, 1993 - Robert Lentz