Common Questions

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                                CIA Questions

  Question: Which CIA is associated with the parallel port?
    Answer: U350 is the parallel port CIA; the other CIA is U300.


  Question: Can the surface-mount CIAs used in the A4000 (and A1200) be
            removed and replaced with sockets for easier replacement in the
            future?
    Answer: [Courtesy of Dale Currie of AmiTrix]
            "These sockets are sometimes called Ultra Low Profile SMT sockets
            for PLCC Packages. The ones we get are AUGAT PCS-SMU Series. I
            believe ASSMANN also make them now, called SMT-PLCC-sockets.
            There are probably others.

            They are only about half the height of a normal PLCC socket, and
            have flat pins turned underneath with slots in the bottom of the
            socket all around the inside edge, such that the pins sit on the
            SMT pads and you can solder them through the slots in the bottom
            of the socket. Needless to say, it's a very delicate operation,
            requiring a good iron with a very fine tip, a steady hand, and
            quite often the assistance of a magnifying glass/lamp.

            Getting the CIAs off intact in the first place is another story.
            That requires some rather expensive gear (we use a PACE station,
            $1500-2000 CAN with all the atachments), but does a nice job. The
            only other way destroys the existing chips by cutting their pins
            and removing them one by one after the chip body has been freed.
            I wouldn't recommend it, unless you're very experienced, it's
            quite easy to destroy a pad/trace by overheating."

            Mr. Currie may be contacted at

              AmiTrix Development
              5312 - 47 Street
              Beaumont, Alberta, T4X 1H9
              Canada
              Phone or Fax: 1+ 403-929-8459
              Email: sales@amitrix.com or support@amitrix.com
              http://www.networkx.com/amitrix/index.html

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                              Memory Questions

  Question: What type of memory does the A4000 use?
    Answer: The A4000 comes with 2M of Chip RAM, either in a single SIMM or 
            surface-mounted on the Motherboard. There are four SIMM sockets
            for expansion memory (Fast RAM). These sockets hold 72-pin SIMMs,
            either 1M or 4M in capacity, 80 ns or faster. It is not possible
            to mix 1M and 4M sizes, although it has been reported that 8M
            SIMMs can be used in place of two or four 4M SIMMs. To fit
            properly, these SIMMs must be single-sided modules. The total
            motherboard Fast RAM limit is 16M, regardless of SIMM 
            combinations. (These specifications describe the motherboard
            memory; expansion boards may use other types of memory.)


  Question: Can the A4000 use 36-bit SIMMs, instead of 32-bit?
    Answer: Yes. The extra parity bits are ignored.

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                           Floppy Drive Questions

  Question: Why does the floppy light flash every so often, even with no disk
            in the drive?
    Answer: This is a result of the system polling the drive to see if a
            floppy has been loaded.


  Question: Why doesn't my second floppy drive work in high-density mode?
    Answer: Check for the proper setting of jumper J351 (see Internals/
            Motherboard Jumpers). See also Floppy Drive Cable Problems.


  Question: Will normal PC-type *double-density* (720K) 3.5-inch floppies
            work in the A4000?
    Answer: Yes, but you may encounter a couple of problems. First, many
            PC-type floppies are not jumpered to support a diskchange signal.
            Enabling this may be as easy as moving a jumper, or it may
            require unsoldering, moving, and resoldering a surface-mount
            part. Secondly, many of the PC-type floppy drives connect the
            diskchange signal to pin 34 of the connector; however, the Amiga
            expects this signal on pin 2. A re-routing of the conductors in
            the cable can solve this, or you can use the DiskChange command
            to manually notify the system of disk changes.


  Question: Will normal PC-type *high-density* 3.5-inch floppies work in the
            A4000?
    Answer: No. [The following text courtesy of Gene Heskett]
            A commodity PC drive runs at normal spindle speed for the drive,
            or 300 rpm. To move data in and out of it in high-density mode
            requires a 500 kilobaud data pump in the floppy path. The Amiga
            chips are only able to handle around 400 kilobauds. The Amiga
            actually runs its floppy data rate at the older double density
            standard of 250 kilobauds.

            To do high density on the older drives, special drives were
            ordered by Commodore that could run a fairly stable spindle speed
            of 150 rpm. If you watch it, you'd swear the drive was going to
            stop, it's that slow. These are the high-density drives for an
            Amiga, and until the chips get a refresh for a higher data rate,
            are the only type of drives that can be used in high density mode
            on an Amiga.

            [Editor's note: some people have managed to modify standard
            drives; however, all reports indicate that these perform
            unreliably at best.]

            I might add that since these custom Amiga drives run at half
            speed, the read signal from the head is only about one-fourth of
            what a standard drive has, and they do require an electrically
            quiet environment for a usable error rate. There are a couple of
            other problems with using the PC drives, too: lack of a ready
            signal for the automatic diskchange detection being one of them,
            and the lack of talkback identify to tell the Amiga what kind of
            a drive it is is another. Even if you could diddle the spindle
            speed down to 150 RPM (as its digital, that's doubtfull) to make
            a high-density drive out of it, you'd still have to have a custom
            driver that puts twice as many sectors on a track. The Amiga
            would otherwise only do the normal double density sectors/track,
            and simply fill the remaining space up with "trailer" bytes till
            the next index pulse came by, thereby wasting half the track. The
            Amiga defaults to double density if the drive doesn't talk back.

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                          IDE Hard Drive Questions

  Question: Can the A4000 support two IDE hard drives?
    Answer: Yes, since IDE supports a master/slave drive setup. Make sure the
            drive jumpers are set properly for two drives. You might have
            problems with two different brands of drives working together;
            this depends on the age and type of the drives.


  Question: Can the A4000 use IDE hard drives larger than 512M?
    Answer: Yes. The supposed "limit" of 512M is a limitation of the BIOS in
            MS-DOS machines, and the A4000 is not subject to this limit. The
            maximum supported partition size is 2G, and the maximum drive
            size is 4G. If you want to fully use larger drives, you'll have
            to look into alternative filesystems like AFS.


  Question: Can "EIDE" or "Fast ATA" hard drives be used in the A4000?
    Answer: Yes. These are just different names for revised versions of IDE,
            and should work fine with the A4000's on-board IDE controller.

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                          SCSI Hard Drive Questions

  Question: Does the A4000 come with a SCSI or SCSI-2 hard drive controller?
    Answer: No. The A4000T (tower) model did (and does) come with a built-in
            SCSI-2 controller, though. The A4091 and FastLane expansion
            boards are common Fast SCSI-2 controllers for the A4000, and the
            A2091 is a fairly common SCSI-1 controller.


  Question: Why doesn't SCSI work on the A4000?
    Answer: It does. But because of a bug in early versions of the Zorro-III
            DMA controller (the "Buster" chip), DMA SCSI controllers didn't
            work properly. This problem can be fixed (by replacing the early
            revision 9 Buster with a revision 11 version) or avoided
            altogether (by using a SCSI controller that doesn't use the
            Zorro-III bus, like the one built into the Warp Engine
            accelerator).


  Question: What are SCSI terminators?
    Answer: Terminators are resistor packs attached at both ends of the SCSI
            chain. The resistance reduces ringing and noise on the bus, and
            is necessary for reliable operation. See SCSI Examples.


  Question: What is the proper setup for SCSI termination?
    Answer: Both ends of the SCSI chain need to have terminators, and there
            should be none in the middle. See SCSI Examples.

            Now, the catch: some SCSI devices are not very compliant with the
            SCSI specification, and require oddball setups. Devices made
            within the last couple of years are usually pretty compliant.


  Question: Can a SCSI-1 drive be used with a Fast SCSI-2 controller?
    Answer: Yes, and the reverse will also work. SCSI-1 and SCSI-2 (and Fast
            SCSI-2) are compatible. Of course, a SCSI-1 drive won't go any
            faster when plugged into a Fast SCSI-2 controller; neither will a
            Fast SCSI-2 drive connected to a SCSI-1 controller go any faster
            than SCSI-1. See SCSI Examples.


  Question: Why does my hard drive "stutter" every fifteen minutes or so,
            without the drive light coming on?
    Answer: The drive is performing thermal recalibrations ("t-cals") to make
            certain that the heads remain centered over the tracks as the
            platters heat up. The so-called "AV" drives spread out t-cals so
            this momentary interruption doesn't occur during "live" video or
            sound recording or playback.


  Question: What is the pin-out for a DB25 SCSI connector? What about the
            standard 50-pin SCSI header?
    Answer: See the Drives/SCSI Pin-Outs section for both.


  Question: Will SCSI hard drives meant for the Mac work on an A4000?
    Answer: Yes. The cable included with most external Mac hard drives is a
            DB25-to-Centronics 50 adapter, and this will work on a SCSI
            controller with DB25 external SCSI port. Software is available
            for accessing an existing Mac filesystem, so file interchange
            with a portable SCSI device is possible.

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                              CD-ROM Questions

  Question: Will an EIDE CD-ROM drive work with the A4000's IDE interface?
    Answer: Yes. See the disk/misc and disk/cdrom sections of Aminet for
            drivers to work with these CD-ROM drives. Beware of pseudo-IDE
            CD-ROM drives, like the older Mitsumi, Panasonic, and Sony
            drives, which will not work unless you have a special interface
            board for them.