Newsgroups: comp.sys.mac.hardware
Subject: Centris & Quadra 800 Video Capabilities (long)
From: Dale_Adams@gateway.qm.apple.com (Dale Adams)
Date: 9 Feb 93 23:06:10 GMT
Organization: Apple Computer, Inc., Cupertino, CA
Built-In Video on the Macintosh Centris 610/650 and Quadra 800
There will probably be a number of questions which arise concerning the
built-in video capabilities of the new Macintosh Centris 610 and 650, and
the Quadra 800. In anticipation of these questions, here is an article
(similar to that which I posted for the earlier Quadra machines) which
provides an description of these video capabilities. This article
discusses a few general video topics, details how to wire the video
connector sense pins to access all the supported video modes of these
machines, and describes the memory configurations necessary to support
each of the video modes at specific pixel depths. (I am the designer of
the video hardware for the Quadra 700/900/950/800 and the Centris 610/650,
you can be reasonably sure this information is accurate.)
General Video Design Philosophy
--------------------------------------
The video hardware design of the Centris 610/650 and the Quadra 800 is
highly derivative from the earlier Quadra machines. However, one of the
main goals of these CPUs (and perhaps the #1 goal) was to reduce the cost
of the machines relative to the Quadra 700 and 950, while still providing
the same (or better!) performance. While it was not possible to
significantly reduce cost while maintaining the exact feature set of the
earlier Quadras, most of the Quadra video features were carried through to
the Centris 610/650 and Quadra 800. The main exceptions are support for
Apple convolution (flicker reduction) for NTSC and PAL, and support for 24
bits per pixel (bpp).
The video hardware for all three CPUs, the Centris 610 (C610), Centris 650
(C650) and Quadra 800 (Q800), is virtually identical. The only exception
is that the C610 only requires 100 ns VRAM, while the C650 and Q800
require 80 ns VRAM.
The maximum supported pixel depth is 16 bpp. This is not a matter of the
amount of VRAM in the machine - it is a hardware limitation The RAM/DAC
used by all three machines simply does not include the hardware required
to do 24 bpp on any display. The same is true for the lack of support for
Apple convolution - the hardware necessary to do this is not present in
the machine.
24 bpp support was dropped for a number of reasons:
1) Cost reduction. It is still relatively expensive to provide the 24
bpp support offered by the Q700 and Q950. It would not have been possible
to hit the price point of the C610 while still offering 24 bpp.
2) Marketing research data has shown that a very large percentage of
Quadra users do not use the onboard video, but rather use an accelerated
video card capable of driving a 2-page display at 24 bpp. Since it was
not reasonable to burden the price of every C610, C650 and Q800 with the
cost of a 2-page 24 bpp frame buffer, the 24 bpp feature was dropped
altogether (with a net result of a substantial decrease in cost).
3) 16 bpp offers most of the advantages of 24 bpp, without much of the
cost and at a higher level of performance. QuickTime MooV playback is
optimized for 16 bpp. Also, for casual browsing of image data (e.g.,
scanned images or PhotoCD pictures) 16 bpp is quite adequate and offers
better performance with fewer system resource requirements than 24 bpp.
Convolution support was dropped primarily for cost reasons, and also
because it is very rarely used. NTSC and PAL timing support are still
offered, however. The C610, C650, and Q800 do support all the monitor
types supported by the Q950. This includes support for a 1024 x 768
resolution on 19-inch displays (which was not provided by the Q700).
One area that was positively impacted was performance. At the same
processor clock speed, the video section of these new machines outperforms
the video section of the older Quadras. (I.e., video performance on the
C650 is better than the Q700, and on the Q800 is better than the Q950.)
Due to an improved video memory controller design, one wait state was
removed from many of the frame buffer access cycles. This results in
reduced memory access time overall, and therefore improved performance.
The graphics tests in Speedometer (version 3.11) show an improvement of
roughly 6-10% over the earlier Quadra machines (each running System 7.1).
Supported Display Configurations and Monitor ID Codes
-----------------------------------------------------
The Centris/Quadra frame buffer determines what type of display is
attached to the video connector by examining the state of 3 sense line
pins. The following chart details how these three pins must be wired for
each of the supported display types. For each supported display, the
screen resolution (horiz. pixels X vertical pixels), dot clock
frequency, and the vertical and horizontal scan rates are listed.
Basically, the Centris 610/650 and Quadra 800 support any display, whether
from Apple or from another vendor, that meets one of the following
specifications:
STANDARD SENSE CODES:
Sense pins Hor x Vert Dot Vert Horiz
Display 10 7 4 Pixels Clock Refrsh Refrsh
----------- ----------- ---------- ----- ------ ------
Apple 21S Color 0 0 0 1152 x 870 100 75 68.7
Apple Portrait 0 0 1 640 x 870 57.2832 75 68.9
12" Apple RGB 0 1 0 512 x 384 15.6672 60.15 24.48
Apple Two-Page Mono. 0 1 1 1152 x 870 100 75 68.7
NTSC 1 0 0 underscan-512x384 12.2727 59.94 15.7
1 0 0 overscan- 640x480 12.2727 59.94 15.7
(To produce a color NTSC signal, a RGB-to-NTSC converter is required.)
12" AppleMonochrome 1 1 0 640 x 480 30.24 66.7 35.0
13" Apple RGB 1 1 0 640 x 480 30.24 66.7 35.0
Extended sense codes will be examined if the following sense code is
detected:
1 1 1
NOTE 1 on above monitors: A sense pin value of 0 means that the pin should
be grounded to the C&VSYNC.GND signal; a value of 1 means do not connect
the pin.
NOTE 2 on above monitors: sense pins 4, 7, and 10 are referred to as SENSE0,
SENSE1, and SENSE2 in pinout tables for the video connectors.
NOTE 3: The terms 'underscan' and 'overscan' are used to describe the
active video resolution for NTSC and PAL modes. Underscan means that the
active video area appears in a rectangle centered on the screen with a
black surrounding area. This ensures that the entire active video area
always is displayed on all monitors. Overscan utilizes the entire
possible video area for NTSC or PAL. However, most monitors or
televisions will cause some of this video to be lost beyond the edges of
the display, so the entire image will not be seen.
EXTENDED SENSE CODES:
NOTE for extended sense codes: A sense pin pair value of 0 means those
pins should be tied together (as opposed to grounding the pins to pin 11);
a value of 1 means do not connect the pins. Do _not_ wire any of these
pins to ground.
Sense pins Hor x Vert Dot Vert Horiz
Display 4-10 10-7 7-4 Pixels Clock Refrsh Refrsh
----------- ------------- ---------- ----- ------ ------
16" Color 0 1 1 832 x 624 57.2832 75 49.7
PAL
PAL has two wiring options, using the extended sense pin configuration.
To produce a color PAL signal, an RGB-to-PAL converter is required.
PAL Option 1 0 0 0 underscan-640x480 14.75 50 15.625
overscan-768x576 14.75 50 15.625
PAL Option 2 1 1 0 underscan-640x480 14.75 50 15.625
overscan-768x576 14.75 50 15.625
Note: This sense code also requires a diode between sense pins 10 & 7,
with anode towards pin 7, cathode towards pin 10.
VGA 1 0 1 640 x 480 25.175 59.95 31.47
SVGA 1 0 1 800 x 600 36 56 35.16
To enable SVGA, after configuring and connecting the monitor for VGA, open
the Monitors control panel and select Options. Choose Super VGA from the
dialog and reboot your system.
19" Color 1 1 0 1024 x 768 80 75 60.24
No external monitor (video halted)
1 1 1
Here are the video connector pinouts:
Pin Signal Description
----- ----------- ----------------------------------------
1 RED.GND Red Video Ground
2 RED.VID Red Video
3 CYSNC~ Composite Sync
4 MON.ID1 Monitor ID, Bit 1 (also known as SENSE0)
5 GRN.VID Green Video
6 GRN.GND Green Video Ground
7 MON.ID2 Monitor ID, Bit 2 (also known as SENSE1)
8 nc (no connection)
9 BLU.VID Blue Video
10 MON.ID3 Monitor ID, Bit 3 (also known as SENSE2)
11 C&VSYNC.GND CSYNC & VSYNC Ground
12 VSYNC~ Vertical Sync
13 BLU.GND Blue Video Ground
14 HSYNC.GND HSYNC Ground
15 HSYNC~ Horizontal Sync
Shell CHASSIS.GND Chassis Ground
If your monitor is a VGA type, you can try the following cable pinouts.
Macintosh Video VGA Connector
DB-15
------------- --------------
2 ------------------- Red Video ------------ 1
1 ------------------- Red Ground ----------- 6
9 ------------------- Blue Video ----------- 3
13 ------------------- Blue Ground ---------- 8
5 ------------------- Green Video ---------- 2
6 ------------------- Green Ground --------- 7
15 ------------------- Hsync ---------------- 13
12 ------------------- Vsync ---------------- 14
14 ------------------- Sync Ground ---------- 10
10 ------------------|
7 ------------------| Connect 7 and 10 so the sense pin ID will equal VGA
There are a few issues to keep in mind with VGA monitors:
* VGA monitors will vary depending on the vendor. Check with the vendor
about Macintosh Centris/Quadra compatibility before buying, or better yet,
actually try the monitor with a Quadra to see if it works and if the
quality is acceptable.
* Vendors have different image quality specifications. There may be
significant differences between Apple monitors and the wide range of
VGA monitors. Do a side-by-side comparison of the monitors you are
considering before buying.
* Many third party cable vendors have off-the-shelf cables that should work.
Most NTSC devices use an RCA-type phono-connector and the following
diagram uses that as a reference point. A cable wired as follows may
allow many different brands of NTSC monitors to work on a Macintosh
Centris or Quadra. I would advise you to test the monitor on one of these
machines prior to purchase to see if it meets your expectations.
Adjust the phono-connector side to whatever type of connector is used
(RCA, BNC, etc.). "Tip" is the pin in the center of the connector (the
signal); the sleeve is flange around the outer edges of the connector (the
chassis ground).
Card Connector RCA-Type Phono-Connector
-------------- ------------------------
4 MON.ID1 (sense0) --|
7 MON.ID2 (sense1) --|
11 C&VSYNC.GND --------|
5 GRN.VID -----------------> Tip (signal)
Shell CHASSIS.GND --------------> Sleeve (ground)
By grounding pin 4 and pin 7 to pin 11, the Macintosh Centris and Quadra
CPUs are told that an NTSC monitor is attached. The actual black and
white video signal is on pin 5 and connects to the center (Tip) of the
phono-plug. The shell of the card connector connects to the sleeve of the
phono-plug.
To acquire a color NTSC signal from a Centris or Quadra (or any Apple
Macintosh display card), an RGB-to-composite video converter is required.
VRAM Requirements for Supported Display Configurations
------------------------------------------------------
The frame buffers on the new Centris and Quadra machines support a variety
of pixel depths, from 1 to 16 bits per pixel (bpp). The supported pixel
depths (1, 2, 4, 8, or 16 bpp) depend on the display resolution and the
amount of VRAM present. The fully expanded capability of all three
machines is the same - 1 MB of VRAM. As with the Quadra 950, these
machines can be expanded using 256K (i.e., 128K x 16) 80 nS VRAM SIMMs
(although the C610 only requires 100 ns VRAM).
The following chart lists the Centris 610/650 and Quadra 800 built-in
video's maximum pixel depth supported depending upon the VRAM
configuration:
Display size 512K VRAM 1MB VRAM
----------------- --------- --------
12-inch landscape
384 x 512 16 bpp 16 bpp
12-inch Monochrome
640 x 480 8 bpp 8 bpp
13-inch RGB & VGA
640 x 480 8 bpp 16 bpp
SVGA
800 x 600 8 bpp 16 bpp
15-inch Portrait (b/w)
640 x 870 4 bpp 8 bpp
16" Color,
832 x 624 8 bpp 16 bpp
19" Color,
1024 x 768 4 bpp 8 bpp
2-Page Display (b/w)
1152 x 870 4 bpp 8 bpp
21" Color
1152 x 870 4 bpp 8 bpp
PAL
underscan-640x480 8 bpp 16 bpp
overscan-768x576 8 bpp 16 bpp
NTSC
underscan-512x384 8 bpp 16 bpp
overscan- 640x480 8 bpp 16 bpp
- Dale Adams
Apple Computer, Inc.