MAXG@SUVM.BITNET (Gerry Greenberg) (06/02/89)
A few weeks ago I posted the following question to the net. Over the
next week or so, I received the four responses beneath the question.
Since someone asked me to send them any responses I received (and I was
unable to), I have decided to post them here. As you see, the opinions
of those who responded differ greatly. I will not be going ahead with
such a project, and do not take responsibility for the (in)correctness
of the responses. Thanks very much to those who took the time to
respond---Gerry
QUESTION
>Please don't laugh too hard at this one, I figured I had nothing to lose
>by asking. It seems to me that one of the advantages of having a hard
>drive is that you get to have three drives hooked up to the ST, i.e. 2
>floppies and one hard drive through the dma port. So, knowing
>essentially nothing about the technical end of things, I was just
>wondering if it would be possible to somehow hook up a floppy drive to
>the dma port...??? I guess the idea is that the floppy controller is in
>the ST, whereas the controller for the hard drive is somehow in the hard
>drive set up...BUT, would it be possible to add a floppy controller so
>that you could have 3 floppies, with one through the dma port? Look...I
>told you not to laught too hard, didn't I? It just seemed to me to be
>an interesting possibility. As always, thanks in advance for any
>replies...post to the net, or email directly:
ANSWERS
(1)
Yes, it is a possibility. However, it wouldn't be economical. By the time
you put together the interface to make it run, you would be not far off of
the price for a hard disk. You would need memory and a DMA controller just
between the computer and the floppy. For the price, a hard disk would be
better.
(2)
It's certainly possible. First you get a DMA -> SCSI card (as used in many
hard disk interfaces). Then you plug whatever SCSI device you want into the
SCSI port.
You could plug in floppy drives, optical floppy drives, tapestreamers,
Bernoulli drives, an Apple Mac, whatever. 'Course, for unformatted media
you'll need a suitable formatting utility.
There are companies selling optical drives for the ST...
(3)
My understanding is that controllers like the Adaptec 4000 don't care what
you have hooked up to them, as long the device understands the ST412/506
protocol, which I believe is true for most (all?) floppy drives. I don't
have a floppy piggy-backed on my hard drive, but I don't think I need to
do anything special for that. Ergo: if you want an extra floppy, you can
hook it up to the controller in your hard drive (assuming the controller
*can* be hooked up -- some hard-drives apparently use disks with built-
in SCSI controllers, so there's no way you could connect the hard-drive to
the ST412/506 protocol end). I have a suspicion that you could also open
up your ST and piggy-back the extra floppy on the built-in floppy, but
that's pure speculation.
(4)
I'm afraid thet won't work very well.
The floppy-disk expects to both get/receive the data at EXACTLY
250 000 bits per second. NOw this is not much for the hard-disk port
but it is very much for the ST. The ST would have to handle
ALL the data at EXACTLY (+-1.5%) 250 000 BPS. This in itself is
tough enough, but you'd also have to write a COMPLETE disk-controller
emulator that'd work at that speed (in software). There's no way you
(or anyone else, for that sake) would be able to do that on an 8MHz
machine.
If 3-4 drives are what you want you could go for the discovery-cartridge
from happy-computers, which supports drive C & D. The HAPPY COMPUTER
software does, but I'm not sure TOS does. I'd have to check that.