SCS2SD - Mac Plus bootable solution

[chu-oh]

Here's an update to a previous thread of mine in relation to getting a SCSI2SD booting with the Plus. The Plus is notorious for having a flaky/early version of scsi that doesn't work as expected and as far as I can tell there is no other reports of it working with the SCSI2SD.  

So my previous attempts to make a bootable SCSI2SD drive with codesrc's tutorial (found here) on the Plus resulted in weird behaviour (clicking noises, resets etc). I found out through setting up the SCSI2SD as if it was a HD 20 (see this comment) and using an earlier unmodified version of the HD SC Setup (v7.1) I could install System 6.08/7.0 to the drive and boot from it. However this relies on access to either a way to easily make 800k disks, access to an original floppy with an early version of HD SC Setup or a floppy emu (in which case why would you bother with the SCSI2SD).

So for perpetuity's sake I've copied the driver partition that HD SC Setup created - this can be used in lieu of the ludo.img mentioned in codesrc's tutorial. 

I've tested this with both the revision c rom and a Rominator (which I believe is based on the c revision), it would be great if someone with a Plus running an earlier rom version to give this a shot too. 
 

View attachment Apple_Driver.img

 

[Crutch]

...or a floppy emu (in which case why would you bother with the SCSI2SD).
 

Thanks for this. Regarding this comment, maybe I’m missing something but wouldn’t a SCSI2SD be much faster than a Floppy Emu just by virtue of SCSI vs. floppy port speeds?

 

[chu-oh]

Thanks for this. Regarding this comment, maybe I’m missing something but wouldn’t a SCSI2SD be much faster than a Floppy Emu just by virtue of SCSI vs. floppy port speeds?

Good point, I just found this comparison of the scsi/floppy bus speeds: 

The SCSI bus on the Mac Plus is officially rated at 1.25 MBps/10 Mbps by Apple, although real world testing shows it to be barely over 0.26 MBps/2.1 Mbps – which is still 4x the speed of Apple’s earlier floppy port hard drive.

So I'm guessing the SCSI2SD is 4x the speed of a Floppy Emu. I don't have a Floppy Emu to test with but I'm guessing despite the speed difference the Floppy Emu is preferable on the Plus purely for the out of the box Apple HD 20 SC support and the need to not worrying about partition drivers etc. 

 

[Paralel]

I prefer the Floppy EMU for the fact that its bus powered, so, no external power supplies.

 

[chu-oh]

I prefer the Floppy EMU for the fact that its bus powered, so, no external power supplies.

Anybody know if it's possible to make a cable from one of the serial ports 5v pins to power the scsi2sd? http://www.applerepairmanuals.com/the_manuals_are_in_here/Ports_Pinouts.pdf

 

[ArmorAlley]

According to codesrc.com [1], the V5, V5.1, V5.5 & V6 hardware is powered by 5V via standard Molex 4-pin drive connector, USB, or self-powered using the SCSI host termination power. Can't the Plus supply that?

[1] http://www.codesrc.com/mediawiki/index.php?title=SCSI2SD

 

[chu-oh]

Can't the Plus supply that?

Unfortunately the Plus doesn't provide termination power: https://support.apple.com/kb/TA44647?locale=en_US

 

[ArmorAlley]

Unfortunately the Plus doesn't provide termination power: https://support.apple.com/kb/TA44647?locale=en_US

OK. Would a battery pack do, I wonder? The SCSI2SD requires 2.35W maximum (500mA).

 

[sstaylor]

There is a way of making the Plus provide termination power by installing a diode in the right place; unfortunately my google fu is failing me tonight and I can't find instructions.

I'll keep looking.

 

[Crutch]

I think this is the thread you’re looking for: 







In it techknight says “Simple 4.7ohm resistor, and a regular 4001 diode from the 5V rail to the termination pin of the DB25 connector. presto. Simple mod, and it works”

 

[Dog Cow]

Unfortunately the Plus doesn't provide termination power: https://support.apple.com/kb/TA44647?locale=en_US

This is worth reading too. It was written by an Apple employee. Macintosh SCSI termination rules

 

[chu-oh]

There is a way of making the Plus provide termination power by installing a diode in the right place; unfortunately my google fu is failing me tonight and I can't find instructions.

I'll keep looking.

I've seen a tutorial on how to do this before, but I can't find anything on the Google now either. Did find this from Techknight though:
 



@techknight can you shed some further light on this?

 

[techknight]

youll see a diode foot print behind the SCSI connector, thats where you put the diode. it feeds term power out the db25.