Crutch

This is correct.

You’ll want these drivers most likely. I know they work because I uploaded them. I think your Radius SE will run fine without the drivers, but you may not get the performance boost. https://macintoshgarden.org/apps/radiusware-1990-displays-41-accelerator-29-radiusmath-15

His updated mount is here. It includes an optional “periscope” for mounting an LED where it can be seen thru the little original LED crystal. Indispensable in my view I have one and it works great!

Cdev’s definitely became available before System 6. They existed in System 5 and maybe (??) 4.1. They’re documented in Inside Macintosh: Volume V, so were around by 1987 latest.

Thanks to a link posted in BMOW’s blog years ago, I found the schematics for the “Little Board” which I guess is actually called the Daisy Chain board because it allows one (I believe only if using the 3.5 Drive with an Apple IIgs?) to connect a second drive in series. http://bitsavers.trailing-edge.com/pdf/apple/disk/sony/Apple_3.5_Drive_Schematic.pdf Maybe something is shorted out that damaged the electronics in the floppy mechanisms. I will try to find out.

Thanks for asking. The common factors are the cable (Mac externally floppy port-to-Apple 3.5 Drive) and 3.5 Drive main board. Specifically, inside the 3.5 drive is a “Little Board” that connects to the external cable and has an internal floppy ribbon connector on it. When I received the 3.5 Drive it wouldn’t spin, so I opened it up and connected a known-good 800k drive mechanism to the internal floppy ribbon connector inside the 3.5 Drive (meaning, still using the same external cable and Little Board). Doing so seems to have ruined the previously known-good 800k drive mechanism, since it now acts the same as the one that came with the drive (not spinning), even when removed from the drive and put back inside a known-good Mac Plus. It would be helpful to have a schematic for the Little Board, I suppose. But this all seems very strange to me.

Anyone know where to get a Killy clip (or have a spare)? I have one that’s about to give out from too many mating cycles - pins bending etc. I know I could solder a pin header onto my 68000 but much prefer reversibility for my 128k motherboard.

Bumpity bump. Anyone have any ideas how to fix TWO 800k drive mechanisms that won’t spin? They aren’t “stuck” ... meaning I can freely rotate the rotor thing with my finger. They detect a disk, refuse to spin, then identify the disk as unreadable (and so eject it if during boot ... or ask to initialize it if the Mac is already running ... eject works perfectly well by the way, the issue really seems isolated to refusing to spin). To reiterate: a drive mechanism that came inside an external Apple 3.5 drive was doing this, so I swapped out the drive mechanism with a known good drive, and now they BOTH are doing it. So strange. Both motor circuits fried somehow by an Apple 3.5 drive controller board issue? Anyone have a schematic for these 800k drive mechanisms?

Aaaand it sold.

I think you’ll find it much slower. I run 7.1 on my Plus and 7.5.5 on my 50MHz SE/30. I’m not sure I would love 7.5.5 even on that accelerated Plus ... but I could be wrong! Would be interested to hear if it works.

That’s interesting and a bit surprising, I am running a SCSI2SD 5.1 externally on mine right now just using SCSI bus power. Have you checked the voltages on the accelerator PSU? (I also had to still run the special Plus SCSI settings.) I recall based on something (maybe the GemStart Readme?) that GemStart 3.0 doesn’t like System version above 7.1 but that might be wrong.

@Charadis that’s a nice looking 550c. Swapping in the 3400c keys was clever. I’ve been wanting English keys on my 550c and have a spare 540c keyboard but it’s the wrong color of course. Umm ... anyone have a spare bad 3400c they want to give me?

The floppy interface just doesn’t allow for very fast transfer speeds vs. SCSI, so FloppyEmu is inherently limited. It’s why the original HD20 - which connected to the external floppy port - was so much slower than the 20SC back in the day. You’ll enjoy the much faster speeds with any SCSI device ... especially a SCSI2SD! Glad you got it working!

Wow that’s some good stuff. Thanks for sharing all this material. Sorry if I gave the wrong impression, the SCSI ribbon doesn’t connect to the row of pins in the back but rather to P1 here. It’s definitely not a standard internal SCSI ribbon. My SCSI chip is NOT socketed which makes the GemKit sound kind of weird since one gets the SCSI chip without it. The key to “best SCSI performance” is ... a PSU and a fan? Yes, mine came with a 120v AC powered fan which I replaced with a much quieter Noctua one I spliced into the PSU. By the way while it does provide term power and may be faster, the Plus’s handshake issues are due to code in the 128k ROM and I can confirm that the Gemini alone definitely does NOT fix them ... I had to get updated Rev C ROMs to do that. (The symptoms as I recall include that the Mac won’t boot if any SCSI device in the chain is off when you switch it on, which usually means I can’t restart my Mac with my SCSI2SD hooked up without switching it off and back on with the switch on the back, or I get stuck at a black screen - some timing issue I’d guess, despite having followed these guidelines below)

Here’s my setup, in pieces right now because some pins on the 68k socket atop the Killy clip broke during routine maintenance and I had to order another socket online. Fortunately someone sells these on eBay! It’s a 128k “enhanced” with a pair of rev C Plus ROMs from an eBay seller (I only had the older Plus ROMs which have annoying SCSI issues). The accelerator wouldn’t run with the 64k ROMs. The original fan wanted 120v and was connected to the A/B with test clips, I replaced it with a modern Noctua fan spliced into the accelerator’s PSU. Unfortunately the PSU bracket won’t fit with any of the 400k floppy drive mounting brackets I’ve found, so I had to swap in an 800k drive to make it work. But I am still calling it a 128k not a Plus because the logic board just says “Macintosh”! Interestingly mine doesn’t have the mounting holes (or whatever they are) on MightyJabba’s PSU bracket. The screws you see there are for the PSU itself of course. The A/B connector is easy to remove, you can pull it right up through the hole there. The accelerator doesn’t get in the way. You obviously need to pry the whole thing out with a screwdriver though, which isn’t too bad after the chassis loosens up after a few tries.