Bringing the Internal SCSI drive to the 128k, 512k, and Plus

[retr01]

Overview

The Mac 128k, 512k, and Plus did not have an internal SCSI connector on the mobo. Yet, back in the day, there were solutions. Now, I think there is a great potential to bring that back to use SCSI drives inside those older compact Macs.

This thread will be the discussion and documenting efforts to bring internal SCSI back to the 128k, 512k, and Plus.

Everyone is welcome to help out!

This project will be open source and have a GitHub repo down the road.

Features

• SCSI-1 controller on small PCB that hooks up to the 68000 via killy clip
• Connects to SCSI hard drives and SD drives internally
• About seven times faster than external mass storage hooked up to the floppy port on 128k and 512k
• Power from +5v or +12v (to be determined) rail via pass-through adapter between the analog board and mobo
• 68881 FPU on the controller board

 

[Crutch]

This is very doable on a Plus, here’s a nice solution from cheesestraws but there are many others: https://68kmla.org/bb/index.php?threads/mac-plus-internal-scsi-noninvasive-edition.39231/

I don’t know how you’d do it on a 128k or unEnhanced 512k without a lot more work. The classic solution there involves adding an accelerator!

 

[retr01]

Thanks for sharing the related post from 68kmla, @Crutch. That is helpful to know what others have done. Let me pull some information I have.

 

[retr01]

What was done back in the day for the Hyperdrive internal hard drive in the 512k and Plus by General Computer? Hmmm. I am sure it was some modification somehow to tap the SCSI bus internally. So, I looked at @JDW's video about the internal Hyperdrive hard drive. I realized the connection was piggyback to the pins of the 68000 by the killy clip.

What if a controller was designed to complement any internal SCSI, such as BlueSCSI, MacSD, etc., as an open source GitHub project for the 128k, 512k, and Plus? However, is it possible to build a modern version of the killy clip to make this possible? We may not need another power supply like it was back in the day, as power could be provided via +5v or +12v rail tapped via a pass-through adapter between the analog board and the mobo.

No modifications are needed to the mobo. A new small controller between the modern SD SCSI device and the mobo via the killy clip to the 68000 and tapping power either +5V or +12v rail.

 

[retr01]

@JDW! Do you still have that internal GCC Hyperdrive? Let's check out that controller * as we figure out a new modern small SCSI-1 controller board (smaller than the BlueSCSI or MacSD). Then build a modern killy clip.

BOOM! We got this!

* NOTE: I believe the GCC controller is MFM, not SCSI-1. Yet, by seeing it, we will know what to expect and work on.

 

[retr01]

Here is an example of tapping +12v rail via a 4-pin Molex pass-through. This one is for a 12v fan. So, I believe a pass-through can be constructed with 3D printing and wiring to provide internal power to a modern SD SCSI drive without a USB cable.

 

[retr01]

For reference, this is @JDW's fantastic three part video series about the GCC Technologies hard drives for the older compact Macs back in the day. The internal hard drive is discussed in part 3.

 

[eric]

@BigBadBiologist is working on a similar project

https://twitter.com/i/web/status/1555268689359843329

 

[retr01]

Awesome! Thank you, @eric.

Hello @BigBadBiologist! Would you like to jump here and share your extraordinary progress? So exciting!

 

[Crutch]

Yeah I have a GCC internal HyperDrive also, they are amazing. And there is a ton of internal kit in there. To be clear though those are not actually SCSI drives right?

 

[retr01]

Right, those internal GCC drives use MFM, Modified Frequency Modulation.

We need to figure out to create a controller that is SCSI-1 that we can attach to the 68000 via killy clip. Maybe a small PCB that has a SCSI controller chip and other parts?

 

[retr01]

I came across this post at 68kmla interfacing the SSD for the HyperDrive. Interesting.

SSD for a HyperDrive: A Mini Guide

A while ago I picked up this Macintosh 128K (Original repair thread above), and it turned out to be a HyperDrive 20 equipped system with a 512Ke board. After repairs the board was functional, but mine was missing both the hard drive and the power supply, and trying to find an original compatible...

68kmla.org

 

[retr01]

Interestingly, in the summer of 1986, GCC released HyperDrive 2000 with a 68881 FPU and a faster 16 MHz 68000. I found this advertisement in the August 1986 issue of MacWorld.

 

[JDW]

It seems everyone now understands the HyperDrive I show is not SCSI, I should add that at 7:14 in my GCC HyperDrive 10 video, I show it is an ST-412 interface (instead of SCSI). That interface requires two cables. Also, as I point out in that same video, the HyperDrive was on the market at the same time as Apple's HD20, which was a SERIAL drive that connected to the floppy port. But unlike the Apple HD20, the HyperDrive was unique in that it did not require any floppy to be inserted in order to boot. The HD20 and other drives of the era did require a floppy disk to be inserted so a driver (the HD20 INIT, in the case of the HD20) could be loaded so the drive could boot. GCC built that into their hardware so the HyperDrive user didn't need to worry about floppies. The HyperDrive simply booted up as you would expect any modern drive to do today.

GCC later came out with SCSI versions of their drives, but that happened in a crowded market, and even their accelerator product wasn't enough to keep the drive division of their company solvent. This is why GCC switched to laser printer sales and killed off the drive division. Seems to have been a good choice since GCC as a printer company survived well into the 2000's.

 

[retr01]

Thank you, @JDW.

it is an ST-412 interface (instead of SCSI)

So, it was not an MFM drive?

 

[JDW]

MFM encoding in combination with an ST-412 interface.

Details...

ST-506/ST-412 - Wikipedia

en.wikipedia.org

 

[retr01]

MFM encoding in combination with an ST-412 interface.

Ah! Gotcha. ST-412 was one of Seagate's first hard drives that debuted in 1981. It was normally used in the IBM PC-XT. Yeah, those used the MFM encoding.