Setting up your vintage (classic) 68k Macintosh – Using a SCSI2SD adapter

SCSI2SD adapter card
SCSI2SD adapter card

I recently purchased a SCSI2SD V.5 adaptor (3.5″ and 2.5″) to replace a failing 1980s SCSI HD, and realized once I had it set up I could “image” the Micro-SD card to make boot-able images anyone could use.

So, similar to my entry on setting up using a floppy disk, and setting up using an Iomega Zip Drive, I created boot images for System 6.0.8 and System 7.5.5 for setting up an SD card for use with SCSI2SD.


  1. Your classic 68k Macintosh turns on, and is prompting you to insert a disk.  If your 68k Macintosh does not turn on, or does not show the insert disk icon, you may need to do some repair work before you proceed.
  2. Your classic 68k Macintosh supports an internal SCSI hard drive, and/or an external SCSI hard drive, although you will need to have an enclosure or an external adapter for your SCSI2SD adaptor so to use it externally.  Note, for Powerbook systems that only support 2.5″ SCSI drives, a Powerbook Edition of the SD2SCSI adaptor can be used to replace the internal drive.
  3. You have a SCSI2SD adaptor, you MAY be able to use these images with a Compact Flash card of the correct size and a CF2SCSI adapter, if you can, let me know.
  4. You have a 4GB, 8GB, 16GB or 32GB SD or MicroSD card you plan to use with your SCSI2SD adaptor.

1. Determine if you can use this method

This method will work for the majority of 68k Macintosh computers except: The 128K, 512K, 512Ke.  These three 68k systems do not support internal or external SCSI.  You will need to use one of the other setup methods I’ve previously identified, with the best option being buying and using Floppy-Emu to boot from 400KB SS SD floppy disk images.

For setting up your SD2SCSI card, I suggest either:

  1. using one of the images I’ve provided as long as it’s size is equal to or less than the capacity of your card (see note for size in bytes under the table below).
  2. using one of the smaller images I’ve provided as your SCSI 0 drive, and leaving the rest of your card for use as your secondary + drives (see section 3.2 below).  For example if you have a 2GB card, you might want to use my 1GB image, and setup the rest of your card as a secondary drive (SCSI 1 etc),
  3. creating your own image file and initializing it using SoftMac, or
  4. use some other method of setting up your SD card, e.g. boot from a floppy, CD, etc.

2. Selecting your bootable drive image

I’ve created images containing the minimum versions* of System 6.0.8 and System 7.5.5, and several utilities and drivers (see my entry on creating a bootable disk starting with a disk image).   I haven’t created any image files larger than 2GB, I’m assuming if you have a card larger than 2GB you plan to setup your SD card as multiple virtual drives (see Section 3.2 below).

* you will need to copy the full version of System 6.0.8 or System 7.5.5 on to the images yourself, I can’t due to copywrite.

System 6.0.8System 7.5.5Apple IIe1size in bytes2Sector count3Block Count4
  1. The Apple IIe images have been pre-configured to support the Apple IIe Card.   They have System 7.5.5 as the “blessed” System, and they have been partitioned to include two 32MB ProDOS partitions with the remaining space containing an HFS formatted partition.   See my entry on using an Apple IIe Card for more information (coming soon)
  2. Because manufacturing issues, the number of GB your SD card says it can handle might not be the actual amount.   It could be a bit more, or a bit less.  I have two 4GB cards, one that has a capacity of 4,024,434,688 bytes, and another that has a capacity of 3,965,186,048 bytes. These images were purposely created to be smaller than the maximum stated capacity of the SD card to compensate for bad sectors and variations in storage capacity.
  3. Used in section 3 when configuring the size of your SCSI drive(s).  The default sector size in SCSI SD is 512 bytes, the sector count is the size of the image file in bytes divided by the sector size.   If the sector size is NOT 512 bytes you’ll need to calculate this value for yourself.
  4. Used with DD: bs=1M count=## for extracting the first portion of your SD card to an image file to edit/update.

3. Configuring your SCSI2SD adaptor

You will need to configure your SCSI2SD adaptor based on the size of SD or microSD card you plan to use.  Since I do NOT have a SCSI2CF adapter I can’t provide any guidance for you, or know if you even have to do anything.

**** Remember to write the configuration information down. It is NOT stored to your SD CARD, it is stored on the SCSI2SD adapter. If you switch between cards with different configurations you will need to enter the proper drive sizes for the card before using it, or the “drives” will not be recognized, or worse get corrupted ****

  1. Format the SD card you plan to use, if you are using windows I suggest doing a full format vs. a quick format to make sure the card is wiped clean and has no errors.
  2. Download the correct setup software from CodeSRC, make sure you get the correct software based on your version of the adapter v3/v4/v5 vs. v6.   The software is available for Windows 32, Windows 64, Linux and Macintosh OS X.
  3. Run the setup software
  4. Insert the SD or microSD card in to your SCSI2SD adaptor
  5. Connect the USB cable from your computer to your SCSI2SD adaptor

3.1. If you want to setup your SD card as a single drive

Not recommended, but it’s up to you.  Setting up your SD card as multiple hard drives will make your life simpler.  Under the Mac OS, there are several limitations for what you can do to the drive the System files are installed on.   By having at least 2 virtual drives you can save your self a lot of grief.
Double check that the byte size of your SD card is equal to or greater than than the byte size of the image file you plan to use.

  1. Select device 1
  2. Set the sector size to 512
  3. Set the sector count size based on the size of the image file, e.g. my 2GB image file is 1,971,322,880, so the sector count is 1,971,322,880 / 512 = 3850240
  4. The device size should auto adjust, e.g. for the 2GB image file the size is 1.84 actual GB (a MB, GB etc. should be a multiple of 1024, but for marketing reasons storage uses a multiple of 1000)
  5. You should be able to leave the rest of the settings as the default unless you have a reason to change the values (see Figure 1)
  6. Select save to device
    • If you get the message “Save Failed” you’ve set the total sector size of your Device to be larger than what your card can hold.
  7. Once saving is complete disconnect the USB cable from the SCSI2SD adapter
  8. Eject the SD card from the SCSI2SD adapter go to section 4.
Figure 1: Device 1 configuration

3.2. If you want to setup your SD card as multiple drives:

Double check that the byte size of your SD card is greater than than the byte size of the image file you plan to use.

For this example I’m going to use a 16GB SD card (15,794,700,288 bytes) (see Figure 2), and my 2GB image file (1,971,322,880 bytes) for my SCSI device 0.

  1. Follow the steps from section 3.1 above to setup device 1 based on the size of the image file you selected as your SCSI device 0.
  2. Select Device 2 (Figure 3)
  3. Select Enable SCSI Target
  4. For SD card start sector, select Auto
  5. For this example, because I used 1,971,322,880 bytes for device 1, I now have 13,823,377,408 bytes left to work with, which is equal 26,998,784 sectors.
  6. Putting 26998784 sectors in to the sector count give me a Device 2 with a size of 12.874 GB (Figure 3).
  7. If I wanted Device 2 to be smaller I’d reduce the sector size, and use the remaining sectors in Device 3 (and optionally 4)
  8. I suggest that you leave about 50 to 100MB empty (100,000 to 200,000 sectors) un-allocated at the end of your SD card to prevent future issues if you want to backup and restore the contents of your SD card to a different SD card.  As I mentioned earlier the available space on these cards isn’t standard, and can vary by 50 to 100MB.
  9. Once you’ve finished setting up the Device tabs, press the Save to device button.
    • If you get the message “Save Failed” you’ve set the total sector size of your Device(s) to be larger than what your card can hold.
  10. Once saving is complete disconnect the USB cable from the SCSI2SD adapter
  11. Eject the SD card from the SCSI2SD adapter go to section 4.
Figure 2: Capacity of 16GB card
Figure 3: Device 2 configuration

4. Copying the image file to your SD, microSD or CF Card

I’ve moved this section to a separate blog entry for how I write the images I create to the SD and CF Cards and how to create your own images if you don’t want to use one of mine.

Once your done, re-insert the SD card in to your SCSI2SD adaptor, connect the adapter to your classic Mac’s SCSI bus, and you’re ready to go.

If you used option 3.2 above and created more than one “drive” on your SD card, you’ll need to initialize and partition the additional drive(s).

If you plan to use any System older than System 7.5.2 do not create partitions larger than 2GB, there also seems to be a limit to the number of partitions you can have, I was only able to make 12, this isn’t a limit per drive, this is the total limit across all drives.

5. Extra Steps for the Macintosh Plus

The Macintosh Plus doesn’t fully implement the SCSI standard, to get your SCSI2SD adaptor to work you may need to provide extra power to the adapter through it’s USB port.

Also under the SCSI2SD card’s general settings:

  • Enable Unit Attention = OFF
  • SCSI Selection Delay = 0
  • Respond to short SCSI selection pulses = ON

Thanks to Huxley Dunsany for pointing out the settings, and James Thomson for confirming they worked on a 2nd system.

6. Another Option for setting up your SCSI2SD

Remember you could always start with one of my images set as SCSI 0, but once you have your SCSI 1 drive setup how you want, go back in to the SCSI2SD config software, and switch the SCSI IDs, so that my image becomes SCSI 1 (or later) and your newly created, partitioned drive becomes SCSI 0 (your boot drive).   This will let you create a SCSI 0 boot drive partitioned exactly how you want.

27 thoughts on “Setting up your vintage (classic) 68k Macintosh – Using a SCSI2SD adapter

  1. Thank you very much! I can confirm that the instructions worked on macOS High Sierra and I was able to boot my Macintosh SE without a floppy. I should mention that dd took quite a while for me, around 3 hours.

  2. I’m getting an error from Chrome when I attempt to download these images: is dangerous, so Chrome has blocked it.

  3. Hi. This looks great, and I’m really looking forward to trying it out. Just our if curiosity, once this is set up, is there a way to write additional software to the SD card? There is lots of software one can download, but I’ve no way to write it to a floppy, so I’d love to be able to just write it directly to the SD card. Thanks!

  4. I have the 5.1 board, and am running into issues getting the Mac (SE HDFD) to recognize the SCSI device. Is there any tips/tricks needed to get this going beyond setting the size & ID for the devices? Which firmware version(s) have you been successful with?

  5. Another thing to do with the card: update the vendor/product/revision info so it masquerades as an Apple-original device (eg, the SEAGATE ST225N rev 1.0). The fields are case-and-position sensitive, so you can’t just drop in the names any old way (below, replace asterisk with a space):
    vendor: *SEAGATE
    product ID: **********ST225N
    revision: 1.0*

    With this config, the native Apple SC HD application will recognize the drives; you don’t have to use patched versions, etc., on those old machines that would otherwise ignore them.

    • Thanks for point this out, I’ve used the patched version of Apple SC HD for so long I didn’t even bother trying to spoof a compliant drive.
      Did you get this working with your Mac SE HDFD?

  6. Hi Steve – would this work with a color classic with an LC575 board? Would I be able to do an external install or would I be better off with an internal install for this configuration?


    • Hi CT, not sure, have you modded you CC to 640×480? If so it should see your CC as an LC575 and work. For internal vs. external that’s up to you, when I had it installed in my un-modded CC I was using it internally.

  7. Hey! Thanks for these guides, it was a great and complete set.
    I like your 2GB image and would like to use it as a ‘starting point’. It seems quite complete. Two questions:

    1) Is the RAM affected by the networking stuff on it or can that be further slimmed down?
    2) Assuming I want to have several drives, the first one being your image and the others being simply empty 2GB drives for storage. I have SCSI2SD v6 and a Mac Classic II. How can I achieve this?

    Thanks for your efforts!

    • Hi Daniel,
      1. the networking stuff isn’t enabled by default so there shouldn’t be an impact on your RAM. It’s on the image but would need to be installed.
      2. You can write one of my images to the first part of your SD card, then set up the remaining parts of the card as additional drives following the instructions in section 3.2 of this post.

  8. I wanted to start by first saying THANK YOU for these amazing guides and downloadable disk images – you’ve made it possible for me to get my Mac Plus running nicely with my new SCSI2SD, and I’m really grateful!

    I did want to suggest a small addition to your guide – there are some details specific to the Mac Plus which caused me *days* of headaches, thinking I was missing something or doing something wrong. According to Codesrc (in a page which weirdly never came up for me in Google searches on this topic): “The Mac Plus is troublesome as it’s bootrom code doesn’t follow the SCSI standards. The SCSI standards recommend a SCSI selection abort timeout of 250ms, but the Mac Plus bootroms quit before even 1ms has expired.”

    Make sure “Enable Unit Attention” is OFF
    Change SCSI Selection Delay to 0
    Enable “Respond to short SCSI selection pulses”

    Until a kind person on the 68kMLA forum pointed that out to me, I was going in circles to the point of almost giving up – the Mac Plus would “see” the SCSI2SD, but only when I would boot from a floppy, and even then it was unstable and any software I tried to run from the SD card would lock up almost immediately. Making the changes noted above resolved everything instantly.

    Anyway, thank you again, and I hope the info I’m sharing here helps someone else!

    • Hi Huxley,

      Could you go into more detail about how your SCSI2SD for the Macintosh Plus ?
      Which disk image did you use ? I have copied the 2 go system 6.08 image but the Mac Plus is not seeing the SCSI2SD at all. There is no orange led showing up on boot so the Mac Plus isn’t seeing it.
      Please tell me exactly what options you have checked and unchecked in the SCSI2SD setup utility. Thanks. James

  9. Hi,
    answering to Jim:
    “I have the 5.1 board, and am running into issues getting the Mac (SE HDFD) to recognize the SCSI device.”

    I was planning to buy one, and I’ve seen the Mac SE is supported only by the v.6 board.


    • Wait….what?? V5.1 doesn’t support the Mac SE? Is that why I’ve spent days trying to get this thing to work…and failing?

      • I read that the 5.1’s termination is now software-controlled (using scsi2sd-util), I’m assuming you enabled it? The only other thing I’d suggest (if you haven’t tried already) is treating your SE as a Mac Plus and try providing usb power to your SCSI2SD adapter. See step 5. Extra Steps for the Macintosh Plus.

      • Going through the same thing right now (trying to get a v5.5 external enclosure working on a Mac SE). Did you ever find a way to make this work?

  10. Hi Steve,

    Thank you for your reply. I have now managed to get the SCSI2SD card to work with my Macintosh Plus.
    I have a version 5 card which is smaller in physical size than the version 5.1 or version 6 cards. I have it plugged directly onto the DB-25 SCSI port on the rear of the Mac Plus using the internal IDC 50 pin to external DB-25 adapter designed by Michael McAllister. You also need to use a 25 pin male to male gender changer though so that you can plug it in directly into the rear of the Macintosh Plus. The problem I was having was that the SCSI2 SD card was not receiving any terminator power over the external SCSI bus so was not powering up at all. I then plugged it in via USB to power it up. I restarted the Macintosh Plus and it booted straight away ! Something to bear in mind is that the Macintosh Plus boots from ID 6 first so for the fastest boot time I would set the boot drive to ID6.
    Apparently there is a simple diode and resistor mod which can be done to the Mac Plus which will enable it to provide SCSI terminator power as standard. I have been trying to find out more details about this mod but am having trouble finding anything. If anyone is aware of or has the technical details to perform this mod please do share it with this thread. Thank you once again for providing the bootable disk images.

    • Turns out that the Mac Plus, Mac Portable, 100-series PowerBooks, 500-series PowerBooks, and the PowerBook 1400 don’t supply SCSI termination power. So I’m assuming if you are using a SCSI2SD adapter with any of these you’ll need to provide power through USB.

      For the mod I found:
      Simple 4.7ohm resistor, and a regular 4001 diode from the 5V rail to the termination pin of the DB25 connector.

  11. Hi Steve, followed your tutorial for creating disks for using with SCSI2SD. I have a 16GB card and since we were supposed to limit to 2GB I wondered how I could use the remaining 8GB, since the tool only let you setup 4.

    Then I realized we’re actually creating virtual disks, right? Meaning while it would be good for the first to be 2GB to match your image, the rest don’t necessarily have to and I could partition them later into 2GB partitions?

    I first tried to do the install myself from “floppies” (I have a Floppy Emu) but I was not successful, at some point it asks me for disk 1 again and just cancels the installation saying an error happened and my disk was left untouched… Maybe my install floppy images are bad at some point??

    I just tried your 2GB image, writing it to the card under Windows with the recommended tool (why is it still seen as 16GB though? Is it because the “virtual disk” information only exists on the SCSI2SD device and it just reads and writes to/from the appropriate places? Anyway, writing the 2GB image file, and my LC III booted up 7.5.5 just fine!

    Anything you could recommend to learn about the OS? I have never installed one of these in my life (or really used old macs in the past either).

    One thing I need to figure out which I don’t find on your image is the memory control panel to enable 32-bit addressing and that the OS stops using all my mem (I expanded the LCIII with 32MB for a total of 36MB)


    • Hi Walter, from your message it looks like you got to the point where you were able to boot. Congratulations.
      For your question about the memory control panel. I was only able to include a minimal version of 7.5.5 on my image (copywrite). But I do have another page on my site that explains how to update my images with the full version. See
      I updated this post to more clearly explain that the images can/should be updated before they are copied over.
      Yes, you are right about the virtual disks. Each of my images acts as a physical “disk” and using SCSI2SD each disk gets it’s own SCSI ID. You can set up the remaining space on your SD card using the SCSI2SD control panel however you wish up to a max of 3 other “drives”, each of those “drives” can be larger than 2GB. E.g. a 8GB drive that you partition in to 4 2GB partitions.
      For learning about the OS, I’m not sure, I first learned about using these back in the 90s, so I’ve never really looked for how to guides, I’ve been more focused on keeping a couple alive 🙂

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