JDB8042@VENUS.TAMU.EDU (John D. Baker) (12/02/90)
I am in serious need of replacing my 5.25" disk drives, but am a little
confused over the various kinds of drives offered for replacement.
My current 5.25" drives are a pair of 1978-vintage Apple Disk ][s.
What I would like to do is change my controller to the new style Apple
5.25" controller (DB-19 connector) when I get new drives so that I
won't have hard cables hanging out of the back of my //e.
My problem stems from all the different types of Apple-compatible 5.25"
drives I see available (especially mail-order houses).
Would someone please clarify the following desciptions of various 5.25"
disk drives that I see in ads and comment on the assumptions I have
made about them?
From a Programs Plus advertisement:
AMR: A.5 Half-Height (][+ & //e) ;I assume 20-pin header conn.
A.5C 1/2-Height (//c) ;Sounds like DB-19, but can it
;have a 2nd drive attached?
A5 D 1/2-Height (][gs daisychain) ; I have no idea what
; this means
Apple: Apple 5.25 Drive (//e, gs, C+) ;I presume that it uses the
;DB-19. As it is the only
;one listed, it seems that
;one drive fits all.
Also, the LASER drives:
5.25 LASER/Apple //c ;DB-19, I presume? Support 2nd drive?
5.25 LASER/Apple //e ;20-pin header?
5.25 LASER Daisy chain ;Please explain
I assume that all non-Apple drives (except AE) support 40 tracks.
Basically, it comes down to:
"Which of these drives types would I be able to use on a //e with the
DB-19-style 5.25" disk controller?"
Please do not make recommendations based on the _brand_ but only on
the desciptions given with the drive.
Thanks for the help.
John D. Baker ->An Apple 8" ZCPR3 nut //
PS I know what 'daisychain' means, but how does that relate to differences
in 5.25" drives for Apple //e vs ][gs?alfter@uns-helios.nevada.edu (SCOTT ALFTER) (12/02/90)
In article <901201122247.204030b1@VENUS.TAMU.EDU> JDB8042@VENUS.TAMU.EDU (John D. Baker) writes: >My current 5.25" drives are a pair of 1978-vintage Apple Disk ][s. >What I would like to do is change my controller to the new style Apple >5.25" controller (DB-19 connector) when I get new drives so that I >won't have hard cables hanging out of the back of my //e. You shouldn't need to change the controller as the Disk II controller and the UniDisk/DuoDisk controller are identical, except for the connectors. You could easily make an adapter for your existing card with a DB-19 connector, two 20-pin connectors, and a short length of ribbon cable. If you're interested, I'll send instructions, or there's an article in _Open-Apple_ (I forgot which issue) that gives pinouts for all the different drives. >Would someone please clarify the following desciptions of various 5.25" >disk drives that I see in ads and comment on the assumptions I have >made about them? >[...] >AMR: A.5 Half-Height (][+ & //e) ;I assume 20-pin header conn. Probably. > A.5C 1/2-Height (//c) ;Sounds like DB-19, but can it > ;have a 2nd drive attached? The IIc only accepts one external drive, so it probably doesn't have a daisy-chain connector. > A5 D 1/2-Height (][gs daisychain) ; I have no idea what > ; this means Probably the same as the above, only they give you a daisy-chain connector. ----------------------------------------------------------------------------- Scott Alfter _/_ / v \ Apple II: Internet: alfter@uns-helios.nevada.edu ( ( the power to be your best! GEnie: S.ALFTER \_^_/
reeder@reed.bitnet (Doug Reeder,,,2343817) (12/09/90)
In article <901201122247.204030b1@VENUS.TAMU.EDU> JDB8042@VENUS.TAMU.EDU (John D. Baker) writes:
_My current 5.25" drives are a pair of 1978-vintage Apple Disk ][s.
_What I would like to do is change my controller to the new style Apple
_5.25" controller (DB-19 connector) when I get new drives so that I
_won't have hard cables hanging out of the back of my //e.
Your present card will work fine with adapter cables (20 pin to DB-19)
available from Aplied Engineering, among others. They might dangle a
little, but you could detach your drives without opening your machine. One
advantage to this is that you need not daisy chain.
_AMR: A.5C 1/2-Height (//c) ;Sounds like DB-19, but can it
_ ;have a 2nd drive attached?
Almost certainly DB-19 and could be second, but not first, drive in daisy
chain.
_
_ A5 D 1/2-Height (][gs daisychain) ; I have no idea what
_ ; this means
DB-19 and can be either first or second in daisychain.
_
_Apple: Apple 5.25 Drive (//e, gs, C+) ;I presume that it uses the
_ ;DB-19. As it is the only
_ ;one listed, it seems that
_ ;one drive fits all.
DB-19 and can be either first or second in daisychain.
_
_Also, the LASER drives:
_ 5.25 LASER/Apple //c ;DB-19, I presume? Support 2nd drive?
DB-19 and could be second, but not first, drive in daisy chain.
_
_ 5.25 LASER Daisy chain ;Please explain
DB-19 and can be either first or second in daisychain.
_
Note that "IIc" style drives can be second in a daisy chain or be in a
"daisy-chain of one" by themselves. "IIgs" style drives can be first or
second in a daisy chain. (On the GS, the 5.25 drives go further out on the
daisy chain than any 3.5 drives.)
I reccomend you get two IIc style drives and use them with your existing
card with adapter cables.
A question: can you hook two external 5.25 drives to a IIc+ ?ifar355@ccwf.cc.utexas.edu (David H. Huang) (12/12/90)
In article <15766@reed.UUCP> reeder@reed.bitnet (Doug Reeder) writes: >Your present card will work fine with adapter cables (20 pin to DB-19) >available from Aplied Engineering, among others. They might dangle a >little, but you could detach your drives without opening your machine. One >advantage to this is that you need not daisy chain. I have an old half-height Disk II type drive. Currently, it's hooked up to a Disk II controller card. If I get an adapter cable and hook it up to my Apple 3.5, can I set my GS to scan the slots (will the computer be able to tell if I have a disk in there or not)? Also, will it get rid of that annoying "Slot 6, Drive 2" that shows up in most device selection boxes such as the ones in ShrinkIt and Copy II+? -- David Huang | Internet: ifar355@ccwf.cc.utexas.edu | "My ganglion is stuck in UUCP: ...!ut-emx!ccwf.cc.utexas.edu!ifar355 | a piece of chewing gum!" America Online: DrWho29 |
Kapffer@UAIMZA.MATHEMATIK.UNI-MAINZ.DE (12/14/90)
>I have an old half-height Disk II type drive. Currently, it's hooked up to >a Disk II controller card. If I get an adapter cable and hook it up to my >Apple 3.5, can I set my GS to scan the slots (will the computer be able to >tell if I have a disk in there or not)? Also, will it get rid of that >annoying "Slot 6, Drive 2" that shows up in most device selection boxes >such as the ones in ShrinkIt and Copy II+? > Booting with "scan slots" will be able to detect the absence of a disk in the 5.25" drive and pass on to slot 5 (and a "PR#6" or similar reboot won't try booting forever like the Disk ][ controller). Slot 6, Drive 2 will still show up since there is no reliable way to test for the existance of that drive (although the GS/OS 5.25" driver does something in that direction). Under ProDOS 8 packages like Davex or ProSel offer utils to remove unused drives until the next reboot (or return to GS/OS). It should be mentioned that the ROM boot code for the internal 5.25" controller has a slight problem with disks using the multiple sector read feature timing out to early. This is only a concern with a few disks which have their own bootstrap loader. I have once thrown together a short pre-boot program based on the contents of the ROM on the Disk ][ controller; most disks in question can be booted that way. (An alternative is to reformat track 0 from the usual 2:1 descending to an ascending interleave.) ____________________________________________________________________________ __ M a t t h i a s K a p f f e r email: Kapffer@uaimza.Mathematik.Uni-Mainz.DE
Kapffer@UAIMZA.MATHEMATIK.UNI-MAINZ.DE (01/15/91)
Sorry for the late reply - I didn't see your inquiry before the Christmas break. >When you say timing out too early, could it be possible that the disk >drive motor is turning off for a moment, allowing the diskette to >drop below normal rotation speed, and thus causing read errors? DOS >normally checks to make sure that the disk drive is up to speed >before each sector is read, while the boot code is simplified to skip >this step. No. The original Disk ][ ROM tried forever to read the sector in question (track 0 / sector 0 on a normal boot), hanging the system when there was no disk in the drive. Beginning with the //c, the boot code limited the number of failed tries so the boot process could be stopped or the next drive be checked (this is what I called "timing out"). >Is this "multiple sector read feature" referring to the count byte in >sector 0 of track 0 which instructs the boot code to keep loading a >sequence of sectors before jumping to $801 ? Yes. Now the problem with reading multiple sectors is that a normal 5.25" disk is formatted with a descending 2:1 interleave (intended for reading a track in 15 to 0 sector order), but the boot ROM reads a track in ascending order (requiring an ascending 2:1 interleave). Therefore, a full rotation is required and the boot code will count at least 15 misses for every sector (readable sector headers with the wrong sector number count as a miss). Since this count (kept in zero page location 3 on the GS - don't know for the //c) is NOT reset after successfully reading a sector, it accumulates enough before the whole track is read to make the boot code abort the process. > >You mentioned reformatting with an ascending interleave, did you mean >to keep the original 2:1 interleave? Yes. Reformatting the track means that the boot code can read it in 2 rotations, avoiding (nearly) all of the misses and not hitting the no-disk-in-drive-limit - besides being MUCH faster. (FYI: All sector numbers mentioned are LOCIGAL (DOS) numbers - looking at PHYSICAL numbers it's a change from 1:1 ascending to 1:1 descending.) >I wonder why Apple (the Woz) didn't just use an increasing interleave >when designing DOS and then allocate files starting with sector 0 of >each new track. As it is, the interleave is descending and the first >sector to be allocated on new tracks is sector $F (this is somewhat >annoying). I suppose it's because counting down to 0 is somewhat easier in assembly (and it woudn't be a problem if the boot code and DOS were consistent). >BTW, what algorithm does your pre-boot program use to overcome the >problem? There are several fixes: 1) Use the contents of the Disk ][ controllers ROM (it will run from any page boundary if the lower nibble of the page number is the slot number of the controller card - for example, $4600 will work) - that's what I did (besides adding some A/S lines to give it a user interface ;-) 2) Reformat the track causing the trouble (usually track 0) into the ascending scheme - Bag of Tricks INIT will happily do that 3) If a bootstrap loader uses the controller ROM to pull in more sectors (maybe on another track than 0) and trick 2 won't fix it, it may be possible to insert a STZ 3 somewhere before the ROM code is called again. >Brian Willoughby >UUCP: ...!{tikal, sun, uunet, elwood}!microsoft!brianw >InterNet: microsoft!brianw@uunet.UU.NET > or: microsoft!brianw@Sun.COM >Bitnet brianw@microsoft.UUCP - Matthias Kapffer