ATKINSON@RUBY.VCU.EDU (Stage Struck) (12/01/89)
Query: Has the following ever been discussed? I like 3.5 diskettes, but even with 3rd party, its awlfully expensive to start up. My idea was for a controller to read/write the DDDS 5.25 360/720k diskettes. I tend to like a disk per subject, and the 720k is about the length of my subjects ( and attention span). Is such a beast available? If not, why? And if this discussion has already happened, what dates so I can try to get them out of the archives? Luther Atkinson@vcuvax for bitnet Atkinson@ruby.vcu.edu for internet.
saa33413@uxa.cso.uiuc.edu (12/02/89)
/* Written 1:31 pm Nov 30, 1989 by ATKINSON@RUBY.VCU.EDU in uxa.cso.uiuc.edu:comp.sys.apple */ /* ---------- "5.25 floppy disk formats" ---------- */ Query: Has the following ever been discussed? I like 3.5 diskettes, but even with 3rd party, its awlfully expensive to start up. My idea was for a controller to read/write the DDDS 5.25 360/720k diskettes. I tend to like a disk per subject, and the 720k is about the length of my subjects ( and attention span). Is such a beast available? If not, why? And if this discussion has already happened, what dates so I can try to get them out of the archives? Luther Atkinson@vcuvax for bitnet Atkinson@ruby.vcu.edu for internet. /* End of text from uxa.cso.uiuc.edu:comp.sys.apple */ A while back (early 1986 or so), there was a product called EquiDisk Plus. It was made by a company called (I think) HM Enterpises. I'll check my back issues of Nibble and get back with you ASAP on that. Anyway, the EquiDisk Plus was a dual-5.25" drive unit. I imagine it used DSDD drives with a special controller to deliver 737K on an ordinary 5.25" disk. Chances are the 3.5" drives put out by Apple (and, later, by other companies) drove the EquiDisk off the market. I don't have one, but they had an excellent idea. The cheapest I've seen 3.5" disks is $0.99 each. I can get 5.25" disks for $.21 each. 5.25" is much more economical. Now that the EquiDisk is no longer with us, what you're talking about is probably an even better idea. Existing Apple drives (Disk 5.25, DuoDisk, maybe even the venerable Disk II) probably could handle double density, at least. You could only go up to 560K this way (280K per side), but anything's an improvement, right? Of course, this controller would also have to be compatible with the existing 5.25" 140K format. ------------------------------------------------------------------------------ ! Scott Alfter ! Keep the Chief--Dump Simon ! ! !--------------------------------------! ! Thisnet: saa33413@uxa.cso.uiuc.edu ! Note that my Bitnet address will ! ! Thatnet: free0066@uiucvme.bitnet ! change, effective 20 Dec 89. If you ! ! (until 20 Dec 89; after ! want to be sure to avoid trouble, ! ! 20 Dec, send mail to ! use my Internet address: ! ! free0066@uiucvmd.bitnet) ! saa33413@uxa.cso.uiuc.edu ! ------------------------------------------------------------------------------
lhaider@pro-sol.cts.com (Lawrence Haider) (12/03/89)
In-Reply-To: message from saa33413@uxa.cso.uiuc.edu >...had an excellent idea. The cheapest I've seen 3.5" disks is $0.99 each. >I can get 5.25" disks for $.21 each. 5.25" is much more economical. I can get them for you at a local dealer (I forget the name right now) for about $.69 each in lots of 50. If you're interested in getting some, set me E-mail and I can try to get some to you, if you're willing to pay the mailing costs. Laer lhaider@pro-sol.cts.com I don't work for this company. I hope I'm not violating any rules of the net by this post. If so, please tell me.
krb20699@uxa.cso.uiuc.edu (12/03/89)
The best I've seen is $0.49 for 3.5"s and $0.19 for 5.25"s. This is
in bulk, of course.
I don't see how paying 2.5 times more for over 5 times more storage
isn't economical. 3.5"s are also a heck of a lot faster. This is in Apple
storage terms. As far as MSDOS types go, you need high density disks (high)
for 1.2 meg 5.25"s. They tend towards the expensive. To get 1.44 meg on
a 3.5", you only need to buy the normal $0.49 3.5" and punch a whole in
a certain spot. Double density, through all my uses, have given identical
"track records" to expensive HD 3.5"s on MSDOS machines.
Of course, 3.5" drives are a bit more expensive, but...
Ken.
ken-b@uiuc.eduUD182050@VM1.NODAK.EDU (Mike Aos) (12/06/89)
Sorry, I didn't wanna include the whole message. They were debating yet another disk format. Hi-density 5.25's....YUCK! Anyway, someone mentioned the cheapest price for 3.5" disks they saw was $.99. Our Users Group sells them for $.69, and I assume they purchase them for less.... Mike BTW-I heard third-party 3.5" drives were selling for $169. I paid $299 for my Apple 5.25". Go with the 3.5"!
ericmcg@pro-generic.cts.com (Eric Mcgillicuddy) (12/06/89)
In-Reply-To: message from saa33413@uxa.cso.uiuc.edu I can't see the disk II working at double density, the heads are too big. you can write to track $23 so use that for extra storage. Hey, one track is better than none!!! BTW the $.21 disks are not rated for 720K, they are only guaranteed up 360k. They can be formatted to 720 or even 1.44M, but I wouldn't put anything you'd want to keep on them. ^^^^^ sorry 1.2M Go for the 3.5", physically stronger higher density and supported by Apple.
sb@pro-generic.cts.com (Stephen Brown) (12/18/89)
In-Reply-To: message from ericmcg@pro-generic.cts.com I think the problem with getting a 5.25 running double density would be more than just the heads being too big. You'd have to double the clock rate, and then the bit cells would be too small (especially at the outer edge of the disk where the rotational velocity is the greatest). Of course, it might be an interesting hardware experiment with a IBM drive and a modified Disk II controller to see if you could get it working on high density disks. UUCP: crash!pro-generic!sb ARPA: crash!pro-generic!sb@nosc.mil INET: sb@pro-generic.cts.com
brianw@microsoft.UUCP (Brian WILLOUGHBY) (12/22/89)
sb@pro-generic.cts.com (Stephen Brown) writes: >In-Reply-To: message from ericmcg@pro-generic.cts.com > >I think the problem with getting a 5.25 running double density would be more >than just the heads being too big. To clarify, its not the size of the heads that is too big - it is the width of the magnetic pattern written by a signle density head that is the problem. Does anyone know if you could simply replace the head (saving the money needed to purchase a complete DD drive) to get double density capabilities? Modifying the Disk ][ card would also be a big headache. The clock rate would probably need to be doubled (this is what they do in the IWM for 3.5" drives). Or perhaps you could just build your own Disk ][ controller with a surplus IWM chip from Sun Remarketing, and use its proven design. The easiest solution (except price) is to buy a SCSI floppy which can handle both IBM and Apple formats and hook this pricey baby up to an Apple ][ SCSI Card. Brian Willoughby UUCP: ...!{tikal, sun, uunet, elwood}!microsoft!brianw InterNet: microsoft!brianw@uunet.UU.NET or: microsoft!brianw@Sun.COM Bitnet brianw@microsoft.UUCP
paul@athertn.Atherton.COM (Paul Sander) (12/23/89)
In article <8520.infoapple.net@pro-generic>, sb@pro-generic.cts.com (Stephen Brown) writes: > In-Reply-To: message from ericmcg@pro-generic.cts.com > > I think the problem with getting a 5.25 running double density would be more > than just the heads being too big. You'd have to double the clock rate, and then the > bit cells would be too small (especially at the outer edge of the disk where > the rotational velocity is the greatest). As it turns out, the bit cell sizes on single-density and double-density diskettes are the same! They use different encoding methods to store the bits, however. Single-density diskettes use an encoding method called FM (Frequency Modulation) that stores a clock bit and a data bit. The clock bit it always present when data are stored (but not always in headers) and the presence or absence of the data bit signifies a 1 or 0. Double-density drives typically store their data in a format called MFM (Modified FM) and stores clock bits only in the absence of data bits, relying on the phase of the bits to distinguish them. There is a second double-density format called MMFM (Modified MFM) that appears to have some advantages over MFM as far as simplifying timing requirements, but I have yet to see any drive controllers that advertise this feature. I know that it is not a standard format. Apple's Disk ][ controller, as I understand it, encodes bits in neither FM nor MFM formats. Further, the encoding algorithm is burned into a PROM on the controller, and is not easily changed. Here are some references for further information: Worth and Lechner Beneath Apple DOS 1981, Quality Software Worth and Lechner Beneath Apple ProDOS 1984, Quality Software SA800/801 Diskette Storage Drive Theory of Operations 1977, Shugart Associates -- Paul Sander (408) 734-9822 | If you must describe both quantity and paul@Atherton.COM | quality of someone else's code, try {decwrl,pyramid,sun}!athertn!paul | "awful lot."
rlw@ttardis.UUCP (Ron Wilson) (01/01/90)
In article <8520.infoapple.net@pro-generic>, sb@pro-generic.cts.com (Stephen Brown) writes: >In-Reply-To: message from ericmcg@pro-generic.cts.com > >I think the problem with getting a 5.25 running double density would be more >than just the heads being too big. You'd have to double the clock rate, and then the >bit cells would be too small (especially at the outer edge of the disk where >the rotational velocity is the greatest). Of course, it might be an >interesting hardware experiment with a IBM drive and a modified Disk II >controller to see if you could get it working on high density disks. The Apple Disk ][ is a "standard" mechanism with a "proprietary" circuit board. In theory, a Disk ][ circuit board could be connected to a high density mechanism, provided the new mechanism's head and stepper connections are compatable.
greyelf@wpi.wpi.edu (Michael J Pender) (01/09/90)
In article <15682@athertn.Atherton.COM> paul@athertn.Atherton.COM (Paul Sander) writes: >Here are some references for further information: > >SA800/801 Diskette Storage Drive Theory of Operations >1977, Shugart Associates > >-- >Paul Sander (408) 734-9822 | If you must describe both quantity and >paul@Atherton.COM | quality of someone else's code, try >{decwrl,pyramid,sun}!athertn!paul | "awful lot." Shugart is my least favorite company in all of creation. Someone gave me a 5 meg hard drive fore free, and I was wondering how to connect it to my Apple if I chose to. I called the company and asked. The technical service person was the RUDEST I've ever dealt with in my life. They didn't have the manual for the drive I had, and the man continually got RUDER and RUDER!! The best he could do was offer to SELL me the manual for an 8 inch floppy drive that supposedly had similar power connections, he wanted $50 for it! I took the 5 meg drive, talked to a friend of mine, and gave it to him. Sometime this summer when he's teaching computer science to the 8 year olds in his class he's going to bring it in and let the class disassemble it. --- Michael J Pender Jr Box 1942 c/o W.P.I. ... (Mankind) has already greyelf@wpi.bitnet 100 Institute Rd. used its last chance. greyelf@wpi.wpi.edu Worcester, Ma 01609 - Gen. MacArthur
sb@pro-generic.cts.com (Stephen Brown) (01/10/90)
In-Reply-To: message from paul@athertn.Atherton.COM [lots of stuff on FM and MFM disk data encoding methods deleted] Whatever you say about Apple's proprietary encoding technique, you have got to admit it's pretty good. Consider that you get 140K per side, or 280K per double-sided disk in single density. That's not too bad in comparison to IBM's 360K /disk double-density. sb@pro-generic UUCP: crash!pro-generic!sb ARPA: crash!pro-generic!sb@nosc.mil INET: sb@pro-generic.cts.com
rlw@ttardis.UUCP (Ron Wilson) (01/11/90)
In article <9060.infoapple.net@pro-generic>, sb@pro-generic.cts.com (Stephen Brown) writes: >In-Reply-To: message from paul@athertn.Atherton.COM > >[lots of stuff on FM and MFM disk data encoding methods deleted] >Whatever you say about Apple's proprietary encoding technique, you have got to >admit it's pretty good. Consider that you get 140K per side, or 280K per >double-sided disk in single density. That's not too bad in comparison to IBM's >360K /disk double-density. > >sb@pro-generic Apple did not use a proprietary format per se. The data encoding technique Steve Wozniak used was around long before he designed and built the Disk ][ prototype (I don't remember where it was originally developped). As it happens, the Commadore 1541 disk drive (and some of the other Commadore disk drives) also use the same encoding technique (I know this because I once analysed a 1541 formatted disk on my Apple //e with a Disk ][ - actually, I could only read the inner most tracks of the diskette: the 1541 rotates the diskette at a constant LINEAR velocity; where as the Disk ][ spins the disk at a constant angular velicity - this allows the 1541 to store even more data than the Disk ][ because it can put 22 sectors per track on the outermost tracks)
sb@pro-generic.cts.com (Stephen Brown) (01/15/90)
In-Reply-To: message from rlw@ttardis.UUCP Ron Wilson points out that Commodore used a similar storage format to Apple's, but by using a different number of sectors on each track, managed to get more data onto a disk. My point which prompted this was a bit blurred. I claimed that 140K per side, or 280K per double-sided single-density disk was pretty good in comparison to IBM's 360K DS DD disks. Perhaps, I should have qualified this a bit further: Apple's storage capacity is darn good, considering the simplicity of the circuitry and the high data transfer rate.. something that the Commodore 1541 fails miserably on both accounts. UUCP: crash!pro-generic!sb ARPA: crash!pro-generic!sb@nosc.mil INET: sb@pro-generic.cts.com
mitch@rbdc.UUCP (Mitch Berry) (01/16/90)
Speaking of Disk drives...i was curious to a couple of things about apples 3.5" disk drives..... 1- why does the regular Mac 800k 3.5 has Two write protect switches, which the HDFD (high desity floppy drive) has a second for detecting a HD disk. 2- what IS the differnce between a 800k 3.5 and a HD 3.5 drive byt apple , just roms? drive head or a lot of the above?? Thrashing Rage (mitch@RBDC) "...its the end of the world...and my Universal Disk controller is fried..."
dseah@wpi.wpi.edu (David I Seah) (01/17/90)
In article <973@rbdc.UUCP> mitch@rbdc.UUCP (Mitch Berry) writes: >Speaking of Disk drives...i was curious to a couple of things about apples >3.5" disk drives..... > >1- why does the regular Mac 800k 3.5 has Two write protect switches, which > the HDFD (high desity floppy drive) has a second for detecting a HD disk. High Density (HD) disks have just one write protect tab, which is in the same place as it is on a regular 800K floppy. The "extra" hole on a high density 3.5" floppy is detected by high density drives. Without the hole, the HDFD will just assume that the disk is a normal double density floppy. Apparently, in many brands of 3.5" disk there is little or no difference in the actual magnetic media used in double and high density disks. There are tools that allow you to punch in the hole without getting destructive plastic shrapnel inside the disk. More daring types can melt a hole into the disk with a soldering iron. Boom! Instant high density disk! You should run some tests on the born-again disk to make sure it can handle life in the fast lane. >2- what IS the differnce between a 800k 3.5 and a HD 3.5 drive byt apple , > just roms? drive head or a lot of the above?? I'm not too sure of the hardware particulars, but it involves different drive electronics and finer heads to handle the increased data density. The stepper motor might be of a finer resolution, so the heads can step to tracks that are much closer together. I have a sneaking suspicion that most 3.5" drive mechanisms today can read/write high density, if the control hardware was designed for it. These are guesses! Guesses! Guesses! -- Dave Seah | O M N I D Y N E S Y S T E M S - M | Internet: dseah@wpi.wpi.edu | User Friendly Killing Machines | America Online: AFC DaveS