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Apple Hard Disk 20SC Restoration / Update


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I love anything with the old Apple logo on it, so when I found a cheap dead Apple HD 20SC on eBay, I had to have it.  And I'd been looking for something to put my MacSD in, thinking that this would be better as an external device so I could use it with both vintage Macs and Apple IIgs.

 

I had never retro-brighted anything before, but I found this premixed Retro-Brite gel which just applies with a paintbrush.  I kept it outside all day in the autumn MN sun, applying new coats every couple of hours, and after only one day it looked great!  Here's the before and after.

 

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After removing the giant 5.25" dead HD, the MacSD screwed right in with the included 3D printed bracket.  I hooked up a 20mA ultra bright green LED to the corresponding pins of the Expansion Port with some jumper wires for the drive activity light.  An SD extension cable runs out of the bottom of the case since you need access to the SD card in order to add CDROM images etc.  And because the MacSD needs no external power, the power supply is really just there for weight and if you get nostalgic to hear the fan running.

 

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Everything works well with my vintage Macs, and I've been able to get it to mount some 32MB ProDOS HD images on my IIgs, but I haven't been able to get a CDROM image working with the IIgs yet.  The IIgs recognizes that a CDROM is connected, but it can't read the CD.  However, I've only been able to test the Deluxe Ware CDROM image from Brutal Deluxe since I can't find any other IIgs CD images...

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GS/OS can read ISO9660 discs provided the HS.FST is installed. If using Apple's SCSI cards, you need to install the SCSICD.Driver in addition to SCSI.Manager and SCSIHD.Manager. RamFAST cards just need the RamFAST SCSI card driver (found onboard the card's ROM drive) as that handles both hard drives and CD-ROM drives in one driver.

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20 hours ago, NJRoadfan said:

GS/OS can read ISO9660 discs provided the HS.FST is installed. If using Apple's SCSI cards, you need to install the SCSICD.Driver in addition to SCSI.Manager and SCSIHD.Manager.

I'm using a GGLabs A2SCSI which is an Apple SCSI rev. C card clone, and I've got all three of those drivers installed.   HS.FST and HFS.FST are installed too.  The Deluxe Ware CD .iso image works fine on my Mac LC III but not on the IIgs for some reason.  I can read the Deluxe Ware .dmg image as an HD on my IIgs however.  It would be nice to have some other IIgs CD images to test out, but I haven't been able to find them...

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  • 2 weeks later...
On 10/6/2020 at 1:57 PM, Byte Knight said:

I can read the Deluxe Ware .dmg image as an HD on my IIgs however.  It would be nice to have some other IIgs CD images to test out, but I haven't been able to find them...

I found a few more IIgs CD images and have the same issue.  The images won't mount as CD images but work fine if you mount them as HD images.  So I guess that's one workaround...

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Because they are essentially HD images. There was no official specification for ProDOS partitions on a CD-ROM, so its really just a raw dump onto the disc. There are Macintosh HFS CD-ROMs like this too (no ISO-9660 file system present on the disc). Apple later created the ISO-9660/HFS hybrid format to allow cross platform readable discs.

 

https://en.wikipedia.org/wiki/Hybrid_disc

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On 10/15/2020 at 3:31 AM, NJRoadfan said:

Because they are essentially HD images. There was no official specification for ProDOS partitions on a CD-ROM, so its really just a raw dump onto the disc. There are Macintosh HFS CD-ROMs like this too (no ISO-9660 file system present on the disc). Apple later created the ISO-9660/HFS hybrid format to allow cross platform readable discs.

 

https://en.wikipedia.org/wiki/Hybrid_disc

Thanks for the explanation - makes sense now.

 

If anyone else wants the IIgs CD "images", they'll be up on my server soon.

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