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BlueSCSI OS 8 guide - So long Sh***Shaver!


Active member
Nearly every (if not every) guide that I see pertaining to BlueSCSI advised that I use a Classic Mac emulator to set up the device. As I intend to share the BlueSCSI as a gift to somebody that isn't as computer savvy as to know how to use Cmd+I to hide or unhide extensions, navigate a file path on a text-level, or configure an emulator and set up a shared directory I was determined to circumvent this supposed requirement.

Secondly, SheepShaver has degenerated into a steaming pile. I do seem to recall a time when emulating was easy and reliable but it is now so painful that I am over-joyed to delete my SheepShaver folder now. On my G4 running Leopard, the App simply would NOT allow me to set preferences without locking up my system so it wouldn't have a directory to boot at all. On my M1, quitting or crashing the app will 4/5 of the time completely lock up my system. Telling it to quit was often followed by my screen going absolutely black while the system was actually still running. I could adjust brightness, sound, even trigger my system warning sound but in the end the only thing I could do was hold the power button until it shut off and restart. Restart I did and no fewer than 30 or so times in the process. Hard to imagine there's something I can run on my M1 in the year 2022 that is such an abhorrent failure. You won't be missed.

I now have a succinct workflow for getting data onto my BlueSCSI to share with my 68k Mac using OS 8! It is as easy as plugging the SD into a modern Mac, mounting the disk image, editing the data on the volume with Finder, ejecting the image and putting the SD back into the BlueSCSI device. This process requires only the built-in software on your modern Mac!

I'm far from an expert at computers and actually pretty new to configuring classics but here are the facts that will help explain why I use my process and how it differs depending on which systems you have available and which you are using your BlueSCSI with. This is going to be a lot of "duh" information to some but please keep in mind that there are many who are beginners in this hobby.

SCSI devices must be attached and removed to the SCSI host machine while the host machine is powered OFF.
SCSI devices must have an ID to avoid conflicts with the controller.
SCSI ID's may be anything from 0-7, however 0, 3, and 7 are reserved for the Internal HD, Internal CD-ROM, and SCSI Controller respectively and should generally not be chosen to ID any other device to make everything easier.
Vintage SCSI device ID's can be selected using ID jumpers, mechanical ID selectors (dials), the cable itself (cable select) and in the case of the BlueSCSI the ID is selected via the naming scheme of the image files.
Your classic Macintosh will boot to the first SCSI ID which has a bootable System folder. Since an internal HD is ID 0, for instance, your Macintosh will default to the HD if it is installed and bootable.
SCSI interface allows daisy-chaining however the LAST device on a daisy-chain must be TERMINATED (using resistors either in a SCSI device or in a stand-alone plug known as a Terminator). The BlueSCSI includes the necessary resistors and so must itself be the last device on the chain.
Read the BlueSCSI manual to understand the general operation of the device. Generally, disk images (virtual disks) are added to an SD card. The name of the image determines several things about how the vintage host machine will see the images and how it will assign their SCSI ID.

Files Formats:
The SD card you intend to use with your BlueSCSI must be formatted in either FAT or exFAT and use the MBR (master boot record) partition scheme. This is supported in Disk Utility, however exFAT support officially begins with OS X 10.6 Snow Leopard. In my experience, FAT is so slow that it's excruciating as a boot device and I highly recommend against it. exFAT is slower than my internal spinning drive on my Quadra 610 but marginally so.

Macs boot from the following file formats and partition schemes:
HFS (Mac OS Standard) Apple Partition Map at least OS 3.0-9.2.2
HFS+ ( Mac OS Extended) Apple Partition Map (PowerPC Only) OS 8.1-9.2.2
APFS (Apple File System) OS 10.13-

Read AND Write support:
HFS (Mac OS Standard) OS 2.1-10.5
HFS+ (Mac OS Extended) OS 8.1-
APFS (Apple File System) OS 10.13-

As you can see, since I'm using MacOS 8 and a modern Mac, if I use HFS+ then I can edit the volume on both systems. It's not recommended to boot OS 8 on an HFS+ volume so I will create two different drives which was a common solution when HFS+ was introduced.

The only missing piece is that you will need a pre-made OS 8 boot volume which I'm happy to share if somebody can suggest a good reliable file host. The zipped file is only about 75MB. I will add a post whenever the file is uploaded.

Here is the step-by-step process for setting up BlueSCSI for an OS 8 system.

Mount an SD card to your Modern Mac.
With Disk Utility, format the SD card as exFAT on the MBR partition scheme. I named my partition "SCSI".
Download the OS 8 image zip. Unzip the file "HD10_512 OS 8.hda" (this is an .img file but leave it as .hda to avoid accidentally attempting to mount it)
Copy "HD10_512 OS 8.hda" to "SCSI".
Read the remaining space on your SD card. We will create one more disk image to take up the empty space.
Use this command in terminal.app:

dd if=/dev/zero of=~/Desktop/Shared.img bs=1032192 count=5500

The "5500" represents the desired size of the image in MB and should be slightly less than the empty space on your SD card. This command results in a 5.68GB disk image named "Shared.img" on the Desktop of your current user.

Do not attempt to mount the resulting image "Shared.img".
Copy "Shared.img" to "SCSI".
You must change the name of "Shared.img" to assign a SCSI ID to the image. Remember to avoid ID 0, 3, and 7. I will name mine "HD40_512 Shared.img". The third character in the name assigns this image with ID 4.

Unmount the SD card and place it into your BlueSCSI. Attach the BlueSCSI to your classic Mac. Power the Macintosh on and immediately hold this command:


# represents the SCSI ID you wish to boot to. In this case, hold 1 so it will boot to "HD10_512 OS 8.hda"
Once booted, Navigate to Macintosh HD/Utilities and open Drive Setup.
You will see your SCSI devices listed. In this case, you should see SCSI device 4 listed as "not initialized". Select it and click "Initialize". Choose Custom Setup and under Partition Scheme, select 1 Partition and make certain it is formatted to Mac OS Extended. Dismiss the warning about only being able to boot with a PowerPC Mac.
The device will now mount to your OS 8 Desktop. Click it to rename it. In my case, I will name it "Shared".

You're all set! Now your OS 8 Macintosh and your Modern Mac can use the same disk. No emulator or bridge machine required.

Hope this helps somebody. Let me know how this works for you as well as where I can share my pre-set image.


Well-known member
I'm hoping someone can make a Mac OS 8 (or 8.1) image for the SCSI2SD. I already made one for some 030 macs, with a guide existing for others, but someone should make this


Well-known member
I'm hoping someone can make a Mac OS 8 (or 8.1) image for the SCSI2SD. I already made one for some 030 macs, with a guide existing for others, but someone should make this
There's no such thing as a BlueSCSI specific image, or a SCSI2SD-specific image. This is an extremely common misconception. So-called "HDA" files are just raw byte-for-byte dumps of an Apple Partition Map-formatted disk image, containing one or more HFS/HFS+ volumes, _exactly_ like you'd get if you dumped the contents off of a rotational hard drive.

You can take an .hda file, write it directly (raw, using dd or whatever else) to an SD card, and boot that in a SCSI2SD, presuming your SCSI2SD is configured correctly, and with same size as (or larger) the source hda file.

You can also do the same thing in reverse, you just have to know what you're doing.


Active member
In fact, if you change the name of the file you create in my step-by-step (the blank image) from "HD40_512 Shared.img" to "HD40_512 Share.hda" the BlueSCSI and OS 8 don't know the difference. The only reason for naming it .img is easy compatibility with a modern Mac's first-party software.

The only reason for leaving my OS 8 image as a .hda is so you don't accidentally mount and format it in modern MacOS.


Well-known member
I didn’t think modern Mac OS could write to HFS+ volumes? They are usually read only. How do you write to the mounted image on the modern Mac?


Active member
HFS (Mac OS Standard) was supported with read/write until some version of Snow Leopard. HFS+ (Mac OS Extended) appears to still be supported by MacOS as of now.

I can mount and edit the HFS+ image completely normally and with only first-party software and I'm using Monterey.

It's possible that many of the read-only images you're mounting are HFS+ but rips of CD-ROM's etc which were made read-only. If you have trouble writing to such an image, just copy and convert it to read/write.