How to write 400k disks on 90's 68k?

[phreakindee]

Newly acquired Mac 128k sitting beside me, no way to get software to it. Now, here's my dilemma.

The next oldest Mac I have is an LC575. It runs system 7.6.1 currently, which does not write 400k disks properly from what I've read. Even using DiskCopy 4.2 it does not seem to do so.

I have 800k DS-DD disks, which you're supposed to be able to write as 400k SS disks. In order to do that, it sounds like I need to run System 6.x.x. Trying to install 6.0.8 ends in an error on my LC575, saying it won't work on that new of a computer.

Is there some way to be able to write disks on my LC575 that my 128k can use? It writes them, but they are not bootable, making them useless to the 128.

 

[porter]

It writes them, but they are not bootable, making them useless to the 128.

How do you mean "it writes them but they are not bootable", do you mean

you can write and read them on the 575

the disks are actually 400K disks as seen in "Get info"

and they have a blessed system folder containing a System 1 or whatever system file and finder

Are they unreadable on the 128k or are they readable but it can't find an appropriate system to run?

 

[phreakindee]

It writes them, but they are not bootable, making them useless to the 128.

How do you mean "it writes them but they are not bootable", do you mean

you can write and read them on the 575

the disks are actually 400K disks as seen in "Get info"

and they have a blessed system folder containing a System 1 or whatever system file and finder

Are they unreadable on the 128k or are they readable but it can't find an appropriate system to run?

No idea about being blessed or not, although I would assume so. The image I wrote from was here, the system 2.0 for 128k

It shows up as 400k total on the 575, but the read 128k reads it and then spits it back out, displaying the '?' disk again

 

[phreakindee]

Well, I am not exactly sure what I just did but, I got it work. Downloaded another image file (which was in .dsk format) and then converted it over to DiskCopy 4.2 .img format, then wrote it, it booted up perfectly. How very odd. Now if I can duplicate this with other programs, I'll be set.

 

[Mars478]

I'll need this too for my 512k.

I downloaded System 4.1,

I have a IIci, where do I go from here.

I only have HD floppies though

 

[phreakindee]

I'll need this too for my 512k.I downloaded System 4.1,

I have a IIci, where do I go from here.

I only have HD floppies though

I used the instructions here more or less. DiskCopy 4.2 did the trick for me, though with DD disks. Sounds like you may be able to format HD as DD if they have not formatted at all yet.

 

[tomlee59]

Although you can often format HD floppies as DD, it's preferable to find some 720K disks from the PC world and use those instead. These disks are the same, media-wise, as 800K Mac floppies. Just format them as Mac disks, and you're good to go.

Office supply stores no longer seem to stock 720K media (at least, not around here), but I see that many online sources continue to sell them (at widely varying prices; shop around).

 

[porter]

Sounds like you may be able to format HD as DD if they have not formatted at all yet.

Even if they are formatted, tape over the hole without the sliding bit of plastic and repeatedly reinitialize until golden brown.

HD disks are made the same as DD, they just pass a higher quality standard.

 

[Mac128]

Well, I am not exactly sure what I just did but, I got it work. Downloaded another image file (which was in .dsk format) and then converted it over to DiskCopy 4.2 .img format, then wrote it, it booted up perfectly. How very odd.

Always use Disk Copy 4.2 to handle the disk images in System 7.0 and up. But this is the key – never mount the newly created 400K disk under the Mac's Finder. Only insert the disk when Disk Copy asks for it, make sure verify and mount is not selected, so you insert the disk when prompted and the disk is spit out when copied. What happens is the 7.6+ Finder updates the database on the 400K desktop which can render it unbootable by an MFS system. You may want to look into directly transferring files out of your OS X Mac and vice-versa.

 

[Mac128]

HD disks are made the same as DD, they just pass a higher quality standard.

What exactly is your source for that? The coatings on an 800K disk are thicker and less coercive. Meaning, the DD disks are have more particles but less magnetism. This is used with a stronger write signal, but fewer bits encoded. In HD media, there are fewer particles, but more magnetized to accommodate the weaker write heads and more more bits encoded. The purpose of this is to cut down on track interference. Therefore, in putting an HD disk in a DD drive, you are combining greater magnetism with a stronger magnet writing the information and resulting in a greater risk of oversaturation and track bleed, despite writing a lower density of information. Likewise on the DD disks, you are using weaker media with a weaker HD drive magnet resulting in poor recording of much more information and increasing the likelyhood of bleed and readability.

Just DON'T DO IT, except for experimentation. Also, the likelihood of buying an unformatted HD disk seems almost improbable to me today. You cannot overwrite a pre-formatted HD disk and expect it to ever function in any way reliably. DD disks are still widely available and inexpensive. Check eBay, lots go up for sale there all the time.

 

[tomlee59]

Mac128 is correct. Although HD and DD media have similar characteristics, they are not "the same media" that have simply been put through more stringent quality checks. There is indeed a difference in coercivity. The difference is not large, but it is not zero.

 

[Mars478]

tape over the hole without the sliding bit of plastic and repeatedly reinitialize until golden brown.

Ehh Really in terms of color?! or is this just a metaphor?

 

[porter]

tape over the hole without the sliding bit of plastic and repeatedly reinitialize until golden brown.

Ehh Really in terms of color?! or is this just a metaphor?

Until you realize it either isn't going to work (bad), or the number of bad sectors doesn't decrease (good).

 

[H3NRY]

A 128 can read & write to an 800K external drive. A 1.4 drive won't work. When I got my Mac in 1984, one of the first upgrades I made was to stick an 800K mechanism from an Apple][ into it. Worked like a champ. The 800K Apple][ drives were readily available, but 400K external Mac drives were scarce as hen's teeth.

You can sometimes get a HD disk to work in a 400K or 800K drive, but the disk will not hold its data for long. The lower density drives don't use enough write current to fully erase or magnetize the HD media.

 

[Mac128]

A 128 can read & write to an 800K external drive. A 1.4 drive won't work. When I got my Mac in 1984, one of the first upgrades I made was to stick an 800K mechanism from an Apple][ into it. Worked like a champ. The 800K Apple][ drives were readily available, but 400K external Mac drives were scarce as hen's teeth.

There's a lot in this that confuses me. First, a 128K cannot format an 800K DS disk (it can format a 400K SS disk in an 800K drive), so I'm curious what method you used (this is mine).

Also, the Apple II UniDisk drive did not come out until September 1985. I'm assuming you got your 128K in '85, not '84. The 400K External drives did not actually hit the streets until May 1984 and of course everyone NEEDED one, desperately. SO I am not surprised they were rare. But by late '85, I can only imagine they were rare because Apple was trying to phase them out with the 800K drives coming. BUT, an interesting bit of trivia here though ... Sony had an entire factory built around the 400K drives. When Apple switched to the 800K drive, they cancelled their outstanding order for the 400K drive, especially considering the Mac XL which also used them was cancelled. However, Sony forced them to take delivery of the full order to avoid laying off employees. This is one reason I suspect the 512Ke did not come out until 4 months after the Plus, when the 512K/800 evidently appeared simultaneously with the Plus in Europe and elsewhere – Apple was trying to unload the drives. So it would seem in late '85 Apple would have had more 400K drives than it knew what to do with.

Finally, the 1.4MB Suprdrive works fine in a 128K with the correct cable, and behaves just like the 800K drive.

 

[H3NRY]

It's been a while so my memory may be fuzzy, but I got my first Mac at work in Nov '83, and bought my own Mac in May '84. A bit later Apple came out with the first 3.5" Apple][ drive which is 800K with a built-in 6502 of its own. Removing the Apple][ controller card left a drive which could be plugged into a Mac, and which the Mac (64K ROM) recognized as a double-sided disk and formatted MFS 800K. There really wasn't anything more to it than that.

Later 1.4 MB and possibly other model 800K drives needed the 128K Mac Plus ROMs to work properly. My old 128 has Mac Plus ROMs in it now, so I can't easily go back to verify the gory details. That poor Mac was the guinea pig for a Dr. Dobbs style 512K upgrade, development of the Beck-Tech 1MB RAM upgrade, the SCSI interface and chassis design of the Micah internal hard drive, and many other hacks. It still runs, by the way. A tribute to Burrell Smith's solid engineering.

 

[Mac128]

It's been a while so my memory may be fuzzy, but I got my first Mac at work in Nov '83, and bought my own Mac in May '84. A bit later Apple came out with the first 3.5" Apple][ drive which is 800K with a built-in 6502 of its own. Removing the Apple][ controller card left a drive which could be plugged into a Mac, and which the Mac (64K ROM) recognized as a double-sided disk and formatted MFS 800K. There really wasn't anything more to it than that.

Well I appreciate that, but your memory is extremely fuzzy. ;-) If you got a 128K Mac in Nov. '83, that was 3 months before anybody else in the world got one (unless you worked for the Apple Macintosh division). The first Mac commercial wasn't even run until Jan. 20, 1984. So you must mean Nov. 84 and then got your Mac in '85. The 800K Apple II drive was released in September '85 in the form of the UniDisk "smartdisk" drive. I have personally obtained one of these drives and attempted to use it with the Mac 128K (bypassing the drive's circuit board). The 128K will NOT format an 800K MFS disk, because the 64K ROM does not have the drivers for a double sided disk and has no idea how to format it. Once formatted, the 128K can read and write and even erase it again. But never originally format it. You must have obtained 800K MFS disks formatted on a 512K which could use the HD20 INIT that told the 64K ROM how to write such a disk. Otherwise, the reason I am asking is that I would love to know if there was a method to get the 128K to format 800K MFS disks on the little sucker, since lost to us (perhaps a third party disk formatting utility?).

Later 1.4 MB and possibly other model 800K drives needed the 128K Mac Plus ROMs to work properly.

Again, I have taken a later 1.44MB Superdrive and attached it to the stock 128K. It functions identically as the compatible 800K drives. Since there is nothing in the 128K ROM that was even aware of SuperDrive SWIM technology two years in the future, I would be surprised if there were any differences which would affect the way a 1.44MB drive works as compared to the 800K which otherwise works perfectly.

 

[H3NRY]

I guess I'll have to dig the old Mac out of the closet and put the 64K ROMs back in it. I was under the impression that the 1.4 drives only worked with the SWIM chips, and didn't respond to the PWM line on the disk interface. I don't think I ever actually tried a "superdrive" on a 128K, so maybe they do work. As for dates, Apple sent us a prototype a few months before release. There were other developers who were seeded with prototypes much earlier.

As for formatting 800K disks with the early ROM and system, I don't remember anything special about it. I was pleasantly surprised to see that double sided disks were recognized and worked as expected. I expect Larry Pina did likewise. I'll check out how my Mac and my 800K drive interact and post part numbers, etc. as I have time. It'll probably be next weekend before I have a chance to tear the old girl down. Hopefully, we'll find a way for you to get disks formatted on your system, though it seems you've found work-arounds already.

As for formatting 400K disks on a late model 68K, wasn't there a utility which formatted disks and gave you the choice of 400K, 800K, and 800K HFS? Wonder if I have copy around here someplace?

 

[Mars478]

As for dates, Apple sent us a prototype a few months before release. There were other developers who were seeded with prototypes much earlier.

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