Robert Davis

Page last modified, 19 November 2000
On this page:

- What the screen colors at boot up mean

- Keep that high density floppy drive clean

- How to skip an IBrowse startup window

- Keep a record of the time you last started the Amiga

- Put your own RAM: icon on the screen

- Upgrade your Amiga 2000 motherboard

- Jumpers on and installing the OS 3.1 ROM IC

- Which pins go where on 50 and 25 pin SCSI connectors

- About the IOmega ZIP drive and the Amiga

- A problem with A3000 fast ram

- Wiring a 9-pin to 15-pin VGA adapter

- Wiring a null modem cable

On other pages:

- To the first hints page

- To the third hints page

- Amiga and modem connections

- Return to my home page

Some important stuff:

All the information in these Hints files involve modifications to software and hardware which I have done myself, and which worked on my Amigas. If you have a problem, you are encouraged to send me e-mail describing the difficulty, but I will not be responsible for any of the changes or modifications you make to your own computer and its software.

There are no complicated graphics on this page. Everything is ASCII, so that even those with just a text based browser will have no difficulty reading this information.

What do those various colors mean as the Amiga boots up?

Next Item: Keep your hd floppy clean.

When the Amiga boots, the screen changes color to indicate the progress of several internal tests. Here is what happens:

The first colors you will see are shades of gray .. dark gray, middle gray, light gray, and then white. The RGB color values are 0x444, 0x888, 0xAAA, and 0xCCC, in that order. Colors shown before the four gray shades are artifacts from the original values in the custom-chip registers and do not indicate a failure.
The failure mode screen colors:
turquoise (0x0CC) (A1000 only) RAM failure in the Kickstart WCS
green (0x0F0) error in the lowest 256 bytes of Chip RAM. Possible causes, defective CIA-A IC or defective Agnus IC.
yellow (0xFE5) an unexpected processor exception before the appropriate system failure message was prepared. This could mean defective hardware or an attempt to access a RAM address where no RAM exists.
red (0xF00) invalid KickStart ROM checksum.
magenta (0xF0F) single-task or cold-start initialization failed.

Here is another interpretation of the Amiga boot colors: Above problems combinedVideo scrambled
REDKickstart ROM errorTwo ICs in A1200, A3000, A4000
BLUECustom chip problemDenise Paula Agnus
LIGHT GREENCIA (U7/U300) problem
BLACKCIA (U7/U300) problemIf not booting
DARK GRAYHardware tested OK
LIGHT GRAYSoftware tested OK
LIGHT GRAYCIA (U8/U301) problemStops at gray, CIA defective
No videoR406 or R215 openR406=1 ohm R215=4.7 ohm
Agnus or Denise defective

If the Amiga caps lock key LED blinks repeatedly at boot up, another series of error messages must be consulted:
one blink . keyboard ROM checksum error
two blinks .. RAM failure
three blinks .. watchdog timer failure
and not part of the official specification, but observed by the keeper of this page:
on the A500, multiple repeated blinks indicate low voltage on the 5-volt line from the Amiga 500 power supply.
Return to top of page.

You must keep your high density floppy drive clean

Next Item: skip one startup window.

Message posters on Usenet often complain that their high density floppy drives are failing. The usual symptoms are not a total cessation of drive operation but errors while reading, writing, or formatting high density disks. These problems are most often due to dust build up in the drive, rather than any actual failure, especially in the Amiga 3000, where the power supply fan sucks air directly through the floppy drives. Operation of the floppy drive with double density disks usually seems not affected.

Of course the problem is the slow speed of disk rotation in the drive when working with high density disks. Such Amiga drives turn at 150 rpm when the drive senses a disk with the extra hole indicating a higher capacity floppy.
When a double density disk is inserted, the drive turns at the normal 300 rpm.
The solution is rather simple. Remove the entire drive from the computer, remove the top metal shield from the drive, and use one of those cans of compressed air to blow all the dust, hair, and collected grunge out of the drive. In the opinion of the AmigaHints author, A3000 owners will have to do this cleaning ritual once a year.
Return to top of page.

How to skip an IBrowse startup window:

Next Item: Remember when you last started the Amiga.

The unregistered IBrowse does allow you to skip one of the startup windows with an easy trick. Create a file named:
It does not matter what is in the file. Then save that file to your envarc: and env: directories. IBrowse will find the file, and skip one of its startup pages, saving you one mouse click.

Return to top of page.

Remember when you last rebooted the Amiga

Next item: Use a custom icon for your RAM: disk
Just a single line in your sys:s/user-startup file and you can keep a record of when you last rebooted your system.
Add date >ram:reboot at the end of user-startup, and then you have the information available, for your use or to use in another program.
Return to top of page.

Put your own RAM: icon on the screen

Next item: Upgrade your A2000 motherboard to version 4.5
First, you need an icon. You can create your own, or use mine, which you may shift-click here to download. Store the file ramdisk.icon somewhere such as on your sys: disk, and add the following line near the top of your s:user-startup file.
copy sys:ramdisk.icon
Then reboot your Amiga. Your new icon will take the place of the dafault floppy disk icon for the RAM: disk.

Oh, one more thing, if you want to permanently change the position of the ram-disk icon on your screen, move the icon to where you want it, then snapshot the icon. After the snapshot, copy the file back into the original file (example: sys:ramdisk.icon). The next time you start the computer, the ram-disk icon will be at your saved position.
Return to top of page.

Upgrading an Amiga 2000 version 4.3 motherboard to version 4.5:

Next Item: Installing the OS 3.1 ROM in an A500 or A2000
From "An Update for the Service Technician"
Issue 25 (Apr/May/Jun '89) by Commodore-Amiga.


The following instructions detail the changes which must be implemented to upgrade a U.S. manufactured A2000 PCB from revision 4.0 (or higher) to revision 4.5. Field upgrades are NOT recommended on rev. 3.X PCBs.

1) The following components will either not be installed, or will be removed if installed.

R901, C917, C902 (should not be installed, located left of CN601,
last expansion connector on Amiga bus, near pin 1.)
C910, C911 (fix for Hytek keyboards, located off keyboard connector, CN300.)
C905, C908 (C908 located above crystal X1, C905 located below Gary pin 20.)
C230, C240 (located above U204, U303, the two ICs between the 34
pin drive connector and the 8520 U301.)

2) 1.2 Kickstart ROM is replaced with 1.3 Kickstart ROM
(1.3 ROM is P/N #315093-02).
**You might put a 3.1 ROM in that socket now.**

3) Install RP904, RP905, RP906 only if U205 and U206 are 74HC244 type ICs
(resistor pack is 4.7K ohm X 5, 6 pin, P/N # 902441-31). Do NOT
install if U205 and U206 are HCT type 244. RP905 is located between
U205 and U206, RP906 is located between Paula and Denise, RP904 is
located to the right of Denise.

4) Add .01 uF capacitor on J300. Add this capacitor on solder side of PCB,
from pin 2 (middle pin on connector) to ground (use either of the
ground pads located, on the solder side, down and to the right, above
Paula between pins 46 and 48).

5) Add 3.3K ohm resistor to U605, from pin 11 to pin 20.

6) Add 470 ohm resistor to D800, cathode side, to the second pad from
the left, under CN605. (D800 is located to the left of the real time clock IC at U801).
NOTE: On rev. 4.3 and above this resistor is on PCB as R1000, located to the left of Q302.

7) If R5719 is not present (located off pin 1 of CN400, power connector),
add a 470 ohm resistor between VCC and CPU side of R106. (Use pad
located to the right of U100, the 68000, between pins 11 and 12, and
the pad on the ground trace which runs under pin 14 of the 68000).

8) Replace Gary IC, the 5719, at U102, with a MOS manufactured type, if
it is a Toshiba manufactured type. Part number for Gary is 318072-01.

Return to top of page.

Jumpers for the OS 3.1 ROM IC

Next Item: SCSI 50-pin and 25-pin assignments
Jumper wires for the Amiga OS 3.1 ROMs, at least the ones I have seen, are different from
the jumpers on the 2.04 ROMs, and not well documented by the ROM suppliers.

Here is another look at OS 3.1 ROM jumper installation, specifically for a version 5 Amiga 500 motherboard.
Solder a thin wire to pin 1 of the ROM IC. Leave the other end of this wire free.
Solder a thin wire from pin 21 of the ROM IC to pin 31 of the ROM IC.
Bend up pin 31 of the ROM IC so that pin will not go into the ROM socket.
Insert the ROM IC into the socket, taking care that pin 31 of the IC touches *no* other pin or wire.
Insert the free end of the wire from pin 1 into the socket at location 31, taking care that
the wire does not touch any pin on the IC or any other possible connection.
Check for bent pins, test the computer before re-assembling.

Return to top of page.

Pin assignments for 50 and 25 pin SCSI connectors

Next Item: Making a ZIP drive work with an Amiga
Fifty pin Centronics-style and fifty pin header connectors are the same.
The twenty-five pin connector on the A3000, on some third party SCSI host
adapters, and on devices to attached to Macintosh computers does not have
an adequate number of ground connections. Live with it.

Fifty pin assignment --- and the twenty five pin assignment
n/c means no connection -- gnd means ground

50-pin connector25-pin connector
I/O .. 50I/O .. 03
REQ .. 48REQ .. 01
C/D .. 46C/D .. 15
SEL .. 44SEL .. 19
MSG .. 42MSG .. 02
RST .. 40RST .. 04
ACK .. 38ACK .. 05
BSY .. 36BSY .. 06
n/c .. 34
ATN .. 32ATN .. 17
n/c .. 30
n/c .. 28
n/c .. 26
n/c .. 24
n/c .. 22
n/c .. 20
DBP .. 18DBP .. 20
DB7 .. 16DB7 .. 13
DB6 .. 14DB6 .. 12
DB5 .. 12DB5 .. 11
DB4 .. 10DB4 .. 23
DB3 .. 08DB3 .. 10
DB2 .. 06DB2 .. 22
DB1 .. 04DB1 .. 21
DB0 .. 02DB0 .. 08
all odd pins except 2507 09 14 16 18 24

To make a 50 to 25 adapter, first connect all the grounds on the 25 pin
connector together. Then, connect the data and control lines from the 50 pin
cable to the matching pins on the 25 pin connector. Then connect all the grounds
from the 50 pin cable to the ground bus connection you previously installed on the
25 pin connector. Some systems may require termination power (+5 volts) on pin 26
of the 50 pin connector, or on pin 25 of the 25 pin connector.

Return to top of page.

Making an IOmega ZIP drive work on an Amiga

Next Item: The 9-pin VGA to 15-pin VGA adapter

Of course, we are talking about a SCSI ZIP drive. The older parallel-port ZIP drive
just will not work on an Amiga, without an adapter such as that shown in Bruce Abbott's
construction article, ppazip.lha which is available on aminet.
See the previous AmigaHints page for an explanation of why you cannot just plug in a parallel port ZIP drive.

Recent information indicates that the newer ZIP Plus drive is less capable than
anyone had expected. IOmege does not recommend use of the ZIP Plus on a SCSI bus with
other devices. Furthermore, the ppazip.lha hack does not seem to work
on the Amiga with the ZIP Plus. We need more information.

Two methods of setting up a ZIP drive on the Amiga exist. That which we shall cover here
involves mountlist entries. But using a mountlist means you cannot boot from the ZIP drive
so you may wish to use the RDB (Rigid Disk Block) formatting routine, which is not covered here.

I have only tested these mountlist entries with two dedicated SCSI ZIP drives. If you have
the ZIP Plus drive, with the cable which autodetects SCSI or parallel connections,
please send me E-Mail about your method of making the drive work with your Amiga.

In April 2000, my three and one half year old SCSI ZIP drive began to suffer the click of death. That is, the drive would retract and reinsert the read/write head into the ZIP disk, but fail to read the disk. I have now purchased a SCSI ZIP 250 megabyte capable drive and to my surprise, the disk which had been in the older failed unit was not damaged by the defective ZIP drive. QuarterBack Tools checked the ZIP disk and found all data intact. I have mounted the disk using the mountlist shown below.
When I complete a proper mountlist for the 250-megabyte ZIP disk, I shall post that mountlist here as well.

Concerning MS-DOS formatted ZIP disks, from the factory. I use a recent version of CrossDOS on both my Amigas. I think that the version of CrossDOS supplied with Amiga OS works only with floppy drives. You should purchase the most recent version of CrossDOS, it works much better than older versions.
Disks for either the Amiga or for MSDOS machines may be created using these mountlist entries.
I have tested the MSDOS (clone) format, and I have exchanged disks with my Amiga and
half a dozen Windows 95 boxes, where all worked well.
You probably won't have difficulties with it. Emphasize probably, and keep my E-Mail address
in mind, should you find incompatibilities. I want to know how this stuff works.

To use these entries, copy them into your sys:devs/mountlist file.
Use the command mount zipc: to mount the MSDOS format disk,
and use the command mount zp0: to mount the Amiga format disk.
CrossDOS requires that the last letter of the drive name be either C or D
so ZIPC: or ZIPD: is OK. Amiga format ZIPs may be
named almost anything. One last note: Do not partition the ZIP drive.
Set it up as one 95 megabyte partition. It saves a small amount of memory to not have the extra partitions
and you must mount all the partitions separately. If you create differently sized partitions
on different disks, you will have to add a mountist entry for each possible partition.

/* below entry mounts a clone format 95-meg ZIP disk */
ZIPC:Device = scsi.device

Unit = 5

Flags = 0

Surfaces = 1

BlocksPerTrack = 60

Reserved = 0

Interleave = 0

LowCyl = 0; HighCyl = 2890

FileSystem = L:CrossDOSFileSystem

Stacksize = 4000

Priority = 4

GlobVec = -1

DosType = 0x4D534800

Mask = 0x7ffffffe

MaxTransfer = 0x100000

Buffers = 5

BufMemType = 1

Mount = 1

/* and now the Amiga ZIP mountlist */
ZP0:Device = scsi.device

Unit = 5

Flags = 0

Surfaces = 1

BlocksPerTrack = 68

Reserved = 0

Interleave = 0

LowCyl = 0; HighCyl = 2890

FileSystem = L:FastFileSystem

Stacksize = 4000

Priority = 4

GlobVec = -1

Mask = 0x7ffffffe

MaxTransfer = 0x100000

DosType = 0x444F5301

Buffers = 5

BufMemType = 1

Mount = 1

If you don't have FastFileSystem in your sys:l directory, you may download the latest
version from the (Amiga International) site.
The new FFS really helps if you are going to use very large hard drives on your Amiga, but it is not absolutely necessary for the ZIP. You could replace the FileSystem line in the mountlist with:
FileSystem = FastFileSystem
to use the ROM-based FFS in your Amiga with OS 2 or newer.

Return to top of page.

A3000 fast ram works loose

The Amiga 3000 is unique in its use of ZIP RAM, those memory chips which mount vertically in their sockets. It appears that heating and cooling of those ICs causes them to gradually work out of their sockets. This is actually a common problem in any electronic equipment using socketed integrated circuits. The symptom I have seen on my various A3000 machines is a total lockup of the computer when ambient room temperature goes up.
The solution is time consuming, but simple. Take the A3000 apart, and firmly push the ZIP chips down into their sockets. I have to do that on my main A3000 about once every two years. One or more of the ZIP ICs is always partially unplugged when the lock up symptom appears, usually in the heat of summer.
Return to top of page.

Wiring a 9-pin VGA to 15-pin VGA adapter

Next item: wiring a null modem cable.

Such an adapter is easy to make, assuming you have the correct gender connectors for your
computer and display unit. Only eight wires connect the two connectors, as the 15-pin
has some signals which just don't fit on the 9-pin end of the cable.
pin 1-to-pin 1Red
pin 2-to-pin 2Green
pin 3-to-pin 3Blue
pin 4-to-pin 13Horizontal Sync
pin 5-to-pin 14Vertical Sync
pin 6-to-pin 6Red Ground
pin 7-to-pin 7Green Ground
pin 8-to-pin 8Blue Ground
pin 9-to--N/C-
Return to top of page.

Wiring a null modem cable

It is certainly easier to buy a null modem cable at a computer retailer. But some of us just like to get our fingers into the solder, as it were. Here is the way to wire an Amiga to something else null modem cable.
For use on an Amiga, it is best to not connect the RI and CD lines in the adapter.
Return to top of page.

Created on Amiga