Macintosh Quadra 700

The Macintosh Quadra 700 is powered by a Motorola 68040 processor. This is a popular model for hobbyists and prices on the used market tend to be high compared to other models.

It was the first in a new family of Macs, and was the first Mac to ship in a tower case (a IIcx case on its side, with the label rotated 90 degrees). The Quadra 700 was priced at $6,000.

General Information

The Macintosh Quadra 700 includes several advanced features that provide improved performance over that of members of the Macintosh II computer family. Foremost of those features are the Motorola MC68040 microprocessor and built-in video display hardware. The MC68040 has several built-in features, including data and instruction caches, a memory management unit (MMU), and a floating-point unit (FPU). The computer’s built-in video hardware provides 24-bit color and performance approaching that of the Macintosh Display Card 8•24GC.

Codenames: Shadow, Spike, IIce, Evo. Introduced in October 1991 and discontinued in March 1993. Originally shipped with system software 7.0.1.

CPU

The Quadra 700 features a full Motorola 68040 processor (with FPU) clocked at 25MHz.

Memory

The Quadra 700 has 4MB onboard and offers 4 slots for 30-pin SIMMs.

Video

VRAM expansion includes 3 banks of 2 VRAM slots (6 total found on the board). There is 512KB VRAM built-in to the logic board.

Obviously every display made by every 3rd party monitor vendor can't be supported by the onboard video, but the Quadras do support a much wider range of displays at a higher level of performance than any previous Macintosh. The Quadra 700 and 900 support pixel depths ranging from 1 to 32 bits per pixel (bpp), Apple displays ranging from the 512 x 384 12-inch color monitor through the 1152 x 870 21-inch color monitor, pixel clocks ranging from 12 to 100 MHz, and a variety of industry standards such as VGA, SVGA, NTSC, and PAL. The Mac Quadra video port produces RS-343 RGB, and also provides horizontal, vertical and composite sync outputs. Composite or S-video output is not provided, but can be accomplished by use of an external RGB-to-composite encoder. The Quadra 700 and 900 also support Apple convolution for flicker-reduction on interlaced displays (i.e., NTSC and PAL) at up to 8 bpp. The Mac Quadras automatically detect the type of display attached to the video connector via 3 'sense' pins on the video connector. Depending on the wiring of these 3 pins, software in ROM configures the video hardware for one the supported display types. (A full description of sense pin wiring and supported display types is in the 2nd article.)

The Quadra 700/900 provide the highest built-in video performance of any Macintosh CPU to date. In a (very) simplified graphics model, we could say that performance depends on two main factors: processor horsepower and the bandwidth the processor has into frame buffer memory. These machines already have a fast processor - the 68040 - which runs standard 32-bit QuickDraw. To provide high bandwidth into frame buffer memory, dedicated video RAM (VRAM) was used for the frame buffer, and that VRAM was placed directly on the 68040 processor's local bus. This provides the 68040 the same access time into frame buffer memory that it has into main system RAM. (Transfer rates can exceed 40 MBytes/sec.) In addition, memory options such as fast page mode are supported, which can improve graphics performance for operations such as scrolling, offscreen-to-onscreen pixmap transfers, etc.

In a number of cases the design was optimized for high performance over low cost. A good example of this is 32 bpp operation on Apple's standard 13-inch RGB monitor at 640 x 480 resolution (and this also applies to VGA and NTSC), which is probably the most common color monitor in use on the Macintosh. The actual number of memory bytes needed to support 24 bpp is 640 x 480 x 3 = 921,600. This would seem to fit within 1 MByte of memory (as is the case with the Apple 8*24 video card), but the Quadras actually require 2 MBytes of VRAM for this mode. The 8*24 card supports 24 bpp at 640 x 480 by using a storage mode called 'chunky planar' to fully utilize all its 1 MByte of VRAM. However, this results in having to perform 3 separate memory accesses for each 24-bit pixel read from or written to the frame buffer. (This is done in hardware so software only performs a single read or write.) On a NuBus video card, this inefficiency is partially masked by the synchronization delays which occur at the processor-bus/NuBus interface. However, when frame buffer memory is placed directly on the processor bus, this approach results in a nearly 3X performance degradation. This was judged unacceptable for the Quadras. Each 24-bit pixel occupies one longword (4-bytes) in VRAM, so the Quadras actually provide 32 bpp for the 640 x 480 resolution. This pushes the memory requirement for this mode over the 1 MByte boundary (640 x 480 x 4 = 1,228,800 bytes). Performance is improved still more by another frame buffer architectural feature. Frame buffer memory in the Quadras is organized into 4 'banks' of 512 KBytes per bank. As mentioned earlier, Quadra VRAM can operate in fast page mode. In addition, each bank of VRAM operates in fast page mode independently of the other 3 banks. This causes the number of in-page 'hits' to increase, and thus improves the effective bandwidth into the frame buffer. Also, at 32 bpp, 640 x 480 resolution, each row is set to 4096 bytes, or 1024 32-bit pixels. Each successive row is assigned to a different VRAM bank (modulo 4, of course). This memory organization improves performance during certain commonly performed graphics operations such as vertical scrolling.

In any design there are a number of tradeoffs to be made, and this is certainly true for the frame buffer in the Mac Quadra machines. While the video does operate at 32 bpp on up to 16-inch displays, it does not support 21-inch displays at this pixel depth since this would have significantly raised the cost of the motherboard. (Memory capacity and bus bandwidths would essentially have to double, and this would be expensive.) It does support NTSC and PAL timing, but does not provide a composite video output. While it is much faster than any non-accelerated video card, there are accelerated video cards that are faster (and much more expensive, too, by the way). A separate graphics processor was not added primarily for cost reasons. However, a graphics processor such as the 29000 RISC chip on the 8*24GC card can only speed up the graphics operations that it was designed to know about. If an application program bypasses QuickDraw (which is what most Mac graphics accelerators are designed to speed up), a graphics accelerator will not improve performance, and can actually cause a performance degradation.

Expansion

The Quadra 700 includes two NuBus expansion slots plus a Processor-Direct Slot (PDS) specifically for the PowerPC upgrade option.

There is a ROM slot found on the board but this is not required for normal operation.

Notes

• Unlike most other models of the time, the Quadra 700 does not require recapping on the logic board. The PRAM battery is a concern though and the original battery is known to leak over time, potentially damaging the board. The power supply capacitors should likely be replaced as these will eventually fail due to age.

Modifications

Clock Speed Mod

This procedure should only be attempted by users experienced in circuit board fabrication and repair. You must desolder a component on a multi-layer motherboard. Such boards are fragile and expensive to repair. This is NOT a good first soldering project. The process voids your warranty. If you are not dissuaded by the above, read on and see how a $5.00 part can bring your Quadra 700 up to Quadra 950 performance.

The Quadra 700 has been successfully accelerated by exchanging its CPU clock oscillator for a higher frequency unit. The original oscillator is a 50 MHz unit from which is derived the 25 MHz and 50 MHz clocks used by the 680RC40 processor. Speeds up to 33 MHz are usually attained with new oscillators. Higher speeds are attainable by some individual motherboards. One can reasonably expect to attain 30 MHz. Higher speeds are likely but not guaranteed. There is a small chance that your particular motherboard is incapable of higher speed.

Of the 33 Quadra 700's reported to or modified by myself the results are:

35 MHz    2 machines (custom Fox electronics 70 MHz clocks)
33 MHz   17 machines. Two of which reported as unstable until
               cooling fan added
32.5 MHz 12 machines (had 65 MHz clocks available at low cost)
31.5 MHz  1 machine required cooling fan to operate. Higher speed
               testing pending.
Failed    1 machine failed at 33 MHz. Lower speeds not yet tested
          1 machine with a clip on clock oscillator failed at 32
               MHz to properly access floppy drive

Motherboard destructions: 0

Motherboard damages: 2 episodes of plate through hole damage which
    the users managed to solder through.

Unusual problems: 1 motherboard shorted against the case during
          reassembly. A piece of paper between the motherboard and
          case solve the problem.

33 MHz exceeds the manufacturer expected performance of the Newer Technology Variable Speed Overdrive. Newer guarantees 30 MHz as attainable by all. Of the five VSO's in Seattle I know about, 31 MHz has been the recommended speed. Personally, I have run a motherboard with full stability (except 24 bit video) at over 35 MHz. 24 bit video instability at accelerated speeds prompted me to swap motherboards. My second motherboard has a top stable speed of 30.5 MHz with a VSO. 24 bit stability was not attained until I slowed to 30 MHz. This very same motherboard is running rock solid at 33.3 MHz & 24 bit video is working very well. Apparently, the machine finds a true clock oscillator more palatable than the VSO's synthesized clock. This suggests that speeds over 30 MHz will be more easily attained using true clock oscillators. This observation is confirmed by two other user reports.

The VSO is more expensive but does not require warranty voiding board modifications. I also market a clip on clock modification which uses a true clock oscillator which has a solder free installation. However, I recommend a true soldered installation for highest reliability. Clip on mounts are primarily for users wary of voiding their warranty. One user of my clip on had floppy access problems. It is unknown if that machine would have done better with a soldered installation, but I would not be surprised.

As new user reports arrive, I shall add them to this info file.

Although machines will run more rapidly, this modification pushes the circuits beyond normal operating speeds. Although no reported, long term failures have occurred on Quadra's due to higher speed operation, there is a possibility of shortening the lifespan of components on the motherboard. I have run my Q700 at accelerated speeds for almost 10 months and have not had a board failure. Others have run their VSO's longer. Given this, I doubt this is a very high risk. On the other hand, the machine may be more prone to system crashes. In my experience, this has not been the case. For safety reasons, do not perform this on any mission critical Macintosh.

PARTS

    Clock Oscillators (4 pin TTL or CMOS in 14 pin DIP form factor)
            Check that you are not receiving the half size package!
            Obtain speeds beginning at 50 MHz and higher as you wish
            to attempt. Reasonable values would be 55, 60, 62, & 66.66 MHz
            units. You might try higher speeds as well. The oscillators are
            typically less than $5.00 each mail order.

            You should include the 50 MHz clock in case you damage the
            original oscillator or wish to plug a 50 MHz unit into your
            socket. The original Apple clock oscillator has an Output
            Enable control on pin 1. The units listed below always have
            output enabled. This is not a problem unless you try to use
            a Variable Speed Overdrive with one of the below clocks.

            I obtained my clock oscillators from DigiKey 1-800-344-4539
            Some of their part numbers are:

                50 MHz TTL Clock Oscillator  (part # X121)
                55 MHz CMOS Clock Oscillator (part # SE1509)
                60 MHz CMOS Clock Oscillator (part # SE1510)
                64 MHz TTL Clock Oscillator  (part # X136)
                66.66 MHz TTL Clock Oscillator (part # CTX137)

            Speeds above 66.66 MHz and up to 70 MHz are difficult to find.
            If you wish to try higher speeds, Fox Electronics 1-813-693-0099
            can make 70 MHz clock oscillators on their "Fast Fox" program in
            15 working days. The cost is about $12 each.In ten weeks their
            factory can make any value you wish. Reasonable values to try
            would be 69, 70 and 71 MHz. Ask for TTL in a 14 pin DIP sized
            four pin can.

    Socket: Obtain a 4 pin socket which is in the same form factor as
            a 14 pin DIP package. If you try cutting the extra
            pins off a regular 14 pin socket, be absolutely sure
            no remnants of unused pins can short traces on the
            motherboard. Marc A. Tamsky helpfully suggests using a
            needle nose plier to push the pins out of a machine pin
            socket. It tried it and it work well.

            I used 4 machined socket pins cut from a screw machined
            socket. This allows easier removal should need arise.

    Cooling Fan?: A small, 12 volt muffin fan can be mounted on top of
            the CPU heat sink. Obtain one which has dimensions about
            40 mm square for easier mounting.

            Newer Technology's Variable Speed Overdrive includes a
            cooling fan. However, most machines with modified clock
            oscillators have survived without a cooling fan.
            James MacPhail measured a 4 degree increase was noted at
            33.3 MHz. See later in this document for more thermal
            information. Additional cooling may not be absolutely
            necessary, but one Quadra 700 which I upgraded to 33 MHz
            failed at that speed after two hours of operation. Adding
            a cooling fan allowed that machine to operate reliably.
            If your machine crashes or locks up after several hours of
            operation, you may improve reliability by adding a cooling
            fan.
              
            WARNING: Do not let your Quadra 700 run too long with
                     the cover off. It needs the cover on to properly
                     direct air past the CPU heat sink. One Apple
                     source stated that the motherboard is known to
                     die after 20 minutes of open air operation.        

PROCEDURE

1) Insert usual disclaimer and anti static warnings here. I can take take no responsibility for damage you do to your own machine. Undertake this modification only if you are well qualified. PROCEED AT YOUR OWN RISK.

2) Back up your hard drive. If your Mac is incapable of operating at the speed you select, it may trash the data on your drive. See the warning by Rainer Menes at the end of this document.

3) Remove the top lid of the machine. You will see the floppy disk and hard drive mounted in a plastic tower. Follow strict anti-static precautions and make sure the machine is OFF. Unplug ALL cables, wall and monitor power supply cords from the back of the Mac.

4) Remove the power supply by pulling the plastic interlocking tab on the tower forward and simultaneously pulling the power supply straight up. The tab is a piece of plastic from the left posterior aspect of the tower which extends downward to hook on to the power supply. You may also feel a horseshoe shaped piece at the right portion of the power supply. Leave that alone. The plastic tab from the tower is all you need release.

5) Look at the rear of the tower assembly. You will see the flat ribbon SCSI connector to the hard drive, a power cable and a flat ribbon cable leading to the floppy drive. Disconnect all these from the motherboard. The hard drive power cable connector has a tab which must be squeezed to release it.

6) Unplug the drive activity LED from its clear plastic mount

7) Look down the posterior, cylindrical section of the plastic tower. A Phillips head screw is at the base. Remove it, taking care not to drop it into the case. A bit of gummy glue on your screwdriver is helpful here.

8) Remove the tower assembly by pulling medially the plastic tab on the rear right side of the tower. This tab prevents the tower from sliding posteriorly. Slide the entire tower assembly 1 cm posteriorly then lift the tower assembly straight up and out of the case.

9) Remove the interrupt switch assembly. It is a strangely shaped plastic device at the left, front edge of the motherboard. Pull the middle, rear plastic prong up and forward. The entire device will release.

10) Unplug the speaker cable. Squeeze the plastic tab on the speaker to free it. Swing the fan backwards to free it from the case.

11) Remove the motherboard from the case. Lift the front right corner of the motherboard about 1 mm. This allows it to clear the clear plastic light guide. Slide the motherboard forward about 1 cm. Be very gentle You should not require great force. Once slid forward, the motherboard lifts easily out.

12) Locate the 50 MHz clock crystal. It is a small metal box near the CPU chip. Note and remember its orientation. The new clock oscillators must be aligned with pin 1 (the square corner) in the same orientation. Plug an oscillator in backwards and it will be destroyed.

For your information the pin assignments are:

             --------------
            | 14         8 |           1  Ouput Enable
            |              |           7  Gnd/Case Gnd
            |              |           8  Output
            | 1          7 |          14  V dc (+5)
            L--------------

Very carefully desolder and remove the old clock oscillator. Some of the pins may be bent over. Simply desolder then unbend them. Pin 7 is directly attached to the metal can and absorbs a great deal of heat before melting. Be sure your desoldering iron is hot enough before doing pin 7. It is reasonable to desolder the other pins first. NEVER use any force on the motherboard. The oscillator should practically fall out on its own.

Tip: Put a small amount of soldering flux on the joints before desoldering. This can greatly speed the process, especially on pin 7.

13) Install your socket or socket pins where the old oscillator once was. If you are using socket pins, simply put them on an oscillator and use the oscillator to hold them in place while you solder the pins.

WARNING: If you use plain socket pins, leave the leads of your clock oscillators long enough to keep the can from touching the pins and shorting out the circuit board!

14) Put a 50 MHz clock oscillator into the new socket. You could use the old clock but it has solder on its pins. This can come off inside the socket and cause corrosion problems later. I suggest using a new 50 MHz clock. NEVER plug the old clock oscillator into plain socket pins. The leads are too short to keep the can off the pins.

Again, watch the orientation of the oscillator when you plug it in. It goes in the same orientation of the other clock oscillator next to your new socket. Reversal will destroy the clock oscillator.

15) Install your (optional?) cooling fan system to complete the modification. I used two 1 1/4 inch sheet metal screws through the fan's mounting holes and into the gaps between the fingers of the heatsink to hold the fan in place. Power was tapped from the hard drive's 12 volt line on its power cable. This is the yellow or orange wire on the harness. Ground is either of the middle, black wires. If the fan is too noisy, try tapping the +5 supply (red) instead. The fan will run quietly and slowly but will move enough air to cool the CPU. Some of the very low profile fans will not run on +5. I place four 1/4 watt resistors which have been wired in parallel with each other in series with the fan's 12 volt supply for that type of fan.

16) Reinsert the motherboard and slide it into place.

17) Snap in the interrupt switch assembly and speaker to lock the mother board firmly. Plug the speaker wire back into the motherboard.

18) Reinstall the tower assembly by first placing the right wall of the tower against the right wall of the case with the tower assembly about 1 cm posterior of its intended position. Lower the tower assembly into place while maintaining contact with the right wall of the case. Once fully down, slide the tower assembly anteriorly until it clicks into place.

19) Reconnect the motherboard ends of the cables. DON'T FORGET THE FLOPPY DRIVE CABLE.

20) Replace the Phillips head screw

21) Drop the power supply straight down into place until it clicks in.

22) Plug the hard drive activity light back into its clear plastic mount.

23) Reattach your cables and power cords. Cross your fingers and turn on the Mac. It should make the usual power on chord. If it doesn't, immediately turn of the power and recheck your work. If all is not well, you have my sincere condolences. Please report your failures to the network. The information may help someone else.

Hopefully, all will work normally. Turn the machine back off and replace the 50 MHz clock oscillator with a faster one. Reboot and be astounded.

You must run the machine for many hours before deciding a particular speed is truly usable. With my VSO, a machine lock-up could take 8 hours of operation to occur. In the brief time since modifying my clock oscillator (one week) I have not had a single problem.

Thanks to Rainer Menes, whose comp.sys.mac.hardware article prompted me to try this modification. Thanks also to the following for submitting reports allowing me to summarize the success rate of this procedure:

• Guido Paccagnella
• James MacPhail
• Charles Grosjean
• "Stuart R. Harper"
• Rainer Menes
• "Eric D. Kemp '94"
• Dan Winkler
• Rick Botman
• Mark Newman
• Doug_Steinfeld
• Dustin Boyette
• "Marc A. Tamsky"
• Yushi Kaneda

Good Luck to all who attempt this modification. There is a small but real risk, but you will likely reach Quadra 950 speeds or higher with less than $50 in parts. My personal Q700 at 33.3 MHz with an external memory cache benchmarks faster than a 950. I pass this information along as a very pleased techie.

Guy Kuo

BTW: This same type of mod works for the IIsi, IIfx, Q900, Q950, Centris 610 and Centris 650.

---

And now an important caveat from Rainer Menes

Subject: WARNING: Q700 clock upgrade to 33MHz

Keywords: test your machine very carefull!!!!

Date: 10 May 93 08:43:41 GMT

Hi all,

Yesterday I have encountered on the Q700 of a friend of mine some very strange problems. It looks as if the RAM on the motherboard (80ns DRAM) isn't able to do 33.33 MHz) Sometimes it fails and may damage your hard disk or what ever. This problem varies from board to board. Mine works perfectly under any tested condition with 33.33 MHz.

So here my warning:

TEST your upgraded Quadra 700 very carefully. Run it under full load a mini mum of 24 hours with, for example, a POVRay picture, which uses most of the components in your Quadra 700 (CPU, FPU, SCSI, DRAM, VRAM ...). After that run a memory test for another 12-24 hour. If your Quadra doesn't show any problems you can be 99% sure that it runs at 33MHz. 1% is left over sorry, but no risk no fun.

To be 100% on the safe side make your room a little hotter than normal when you run the tests. This gives you more security and the 1% probability of problems is now smaller than < 1%.

Another tip, if you have not done a backup of your harddisk do it now before you upgrade. This will give you a better sleep with out nightmares.

Good luck for all how have or think about upgrading to 33MHz,

Rainer

---

I include an informative temperature & performance report from James MacPhail

Date: Thu, 22 Apr 93 21:53:49 -0700

Subject: Quadra 700 osc upgrade temp results

I have done some Q700 CPU temperature measurements using an HP 34401A DMM with a Fluke 80TK temperature adapter. I placed the temperature probe on the case of the CPU where it is exposed beside the heat sink, as this is certainly not the place to measure the temperature most accurately, the actual conditions are probably a bit hotter than indicated.

Synopsis: The Q700 has a large design margin for CPU heat dissipation. Increasing the clock speed by 33% increases the CPU case temp about 4 degrees, indicating an increase in power dissipation of 25%.

Machine configuration: Base machine + four 1M SIMM=D5s, Quantum LP52 drive. (no additional cards or VRAM).

With the box closed in the upright orientation, the equilibrium CPU temperature was 37 degrees C at 25 MHz, and 41 degrees C at 33.3 MHz.

The temperature rose rapidly when the cover was removed: it was up 8 degrees in 5 minutes (and still rising). Room temp was 21 C (69 F).

The 68040 designer's handbook predicts Theta(JC) as 2.7 degrees C/Watt. Their calculations use figures of 3 and 5 watts dissipated (typ). Using 5 watts gives a junction temperature of 55 degrees C, so we have oodles of margin (max rating is 110 degrees C).

For those of you who also asked about performance numbers, I did more accurate comparison runs with Speedometer 3.1:

Synopsis: Except for SCSI I/O (the Disk test), 33.3 MHz machine is 33% faster than 25 MHz as expected (including on-board video). faster than 25 MHz as expected (including on-board video).

Extensions off, 24 bit mode, 1 bit two page display, AppleTalk off, System 7.1, Quantum LP52, after quitting Finder (no other applications running):

                KWhet   Dhry    Towers  QSort   Bubble  Queens  Puzz.
Q700 @ 33.3     205.479 27.247  24.960  22.391  23.823  24.105  28.804
Q700 @ 25       155.078 20.390  18.909  17.166  18.000  18.320  21.721
                                                                 
                Perm.   FFT     FPMM    MM      Sieve   BMAve   PRGraf
Q700 @ 33.3     27.170  172.661 154.452 30.250  25.602  63.912  28.347
Q700 @ 25       19.892  127.619 115.839 22.891  19.071  47.908  21.489
                                                                     
                PRDisk  PRMath  PRCPU   PRAve   FPUMM   FPKWhet FPUFFT
Q700 @ 33.3     1.897   136.210 21.898  31.264  13.416  14.827  7.636
Q700 @ 25       1.807   101.943 16.320  23.530  10.733  10.750  5.600

                FPUAve  Mono    2Bit    4bit    8bit    ColorAve        
Q700 @ 33.3     11.960  6.134   6.527   6.785   0.000   6.482           
Q700 @ 25       9.027   4.615   4.878   5.036   0.000   4.843           

32 bit mode (with 8 Mb) tests about 5% faster for video           
MacsBug, AppleTalk, and a bunch of inits hits video about 20% 

Diagrams/Schematics

Gallery

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Documentation

• Macintosh IIcx/IIci/Quadra 700 Service Source
• Macintosh Quadra 700 Developer Note

See Also

• Apple Computer

External Resources

• https://cdn.preterhuman.net/texts/computing/Apple_Service_PDF/68k_Macintosh/quadra_700.mac_iicx.iici.pdf - Apple Service PDF

The Macintosh Quadra Series from Apple Computer

Macintosh Quadra 605 -- Macintosh Quadra 610 -- Macintosh Quadra 630 -- Macintosh Quadra 650 -- Macintosh Quadra 660av -- Macintosh Quadra 700 -- Macintosh Quadra 800 -- Macintosh Quadra 840av -- Macintosh Quadra 900 -- Macintosh Quadra 950

Phase Alternation Line

Small Computer System Interface