Re: Some upgrading questions...

[fsdlb1@aurora.alaska.edu]

In article <D432z9.98L@actrix.gen.nz>, dempson@atlantis.actrix.gen.nz (David Empson) writes:
> In article <D41GFE.55@sunrise.apana.org.au>,
> Aaron Howell <aaron@sunrise.apana.org.au> wrote:
>>
>> Hmmm, I have been out of the apple world for too long. I didn't even know 
>> there was an ide card for the apple.
>> I think, however, that you are confusing ide with mfm/rll.
> 
> Not really.  IDE is limited to two drives (on PCs, at least).  I'm not
> sure if there is a physical limit of two drives (e.g. only two select
> lines) or whether there is a physical limit of four drives but
> software limits it to two.

The IDE controller is really just an interface between the drive and the 
PC bus.  All of the features of either an XT (for 8bit) or an AT controller
(16bit) are contained in the drive's controller card.  This allows for a 
couple of things including the ability of the drive to 'pretend' that it
has a certain # of heads/cylinders when it really does not.  This is why
you only have to pick a BIOS setting that has the same number of logical
blocks.  The drive itself does the translation.  This is also why it is 
VERY important to NEVER low-level format an IDE drive.  
As far as I know, the old IDE standard does have a physical limit of two
drives per card.  The master/slave stuff are the only disk select lines.

> 
> I think the MFM/RLL interface can support up to four drives (using
> separate drive select lines).  I don't recall ever seeing a machine
> with two or more MFM/RLL drives.  Maybe the controllers were usually
> limited to a single drive?
> 
The older MFM/RLL drive controllers could support two drives.  The cable
had a twist in it and the second drive had to go at the connector with
the twist.  I've seen lots of two drive systems and the twist/notwist 
silliness coused many headaches :-/

> I have certainly never seen any IDE interface or drive that mentions
> supporting more than two drives.  Using multiple IDE drives is fraught
> with difficulty and fiddling with jumpers to set up the proper
> master/slave modes.  Some drives are incompatible with others in
> certain combinations, due to differences in opinion about the IDE
> implementation of master/slave.
> 
The new IDE standard can support, I believe, up to 7 IDE devices.  

> SCSI, on the other hand, is limited to seven devices (eight with a
> RAMFast), and not just hard drives.  (Yes, I know you can get some
> other IDE devices for the PC, but I doubt they would be supported by
> Apple II IDE cards.)
> 
 [ SCSI stuf chomped *burp*]
 
> Many new BIOSes have some of these limits increased, allowing larger IDE
> drives to be used.
> 
> I doubt the Apple II IDE cards have this artificial limit (they might
> have a lower limit, though).
> 
The limitations of the IDE drives was mostly due to the IDE standard itself.
The MB limit has been raised on the newer IDE controllers.  The BIOS only 
has a limited role in the IDE transfers.  

> SCSI is the de-facto standard for the Apple II.  SCSI cards are vastly
> more common than IDE cards.

SCSI was designed to be a multi-platform standard.  The only reason IDE
was developed was because IBM drives were so darn common that it was 
cheaper to integrate the controller functions onto the drive itself.  Thus,
IDE is purely a PC standard.  It was never designed to work with anything
other than PCs.   
 
> One problem you might run into with IDE is mounting the drive.  The
> Vulcan Gold got around this by replacing the power supply with a
> combined power supply/drive enclosure.  Can you get cases for external
> IDE drives?

Cableing seems to be the biggest problem for using an external IDE drive.
You can use a SCSI external drive case, but you'd have to hack together 
a cable since IDE uses a 40pin cable and SCSI has a 50pin cable.  Also,
the reccomended maximum cable length for IDE drives is 18".
> 
> A question someone else may be able to answer: how do you partition an
> IDE drive?  I assume software comes with the cards.  Is this
> partitioning scheme compatible with anything else (e.g. the PC)?
> 
Since not all DOS partitions are compatible with each other (you can't read
a DOS 5 or higher partition with DOS 4.x or lower), then I doubt that 
Apple //partitions would be compatiblke either.  

>> With ide you don't need to worry about terminators, or thirty-seven-thousand
>> different submodels of the same card.
> 
Hehehehehe... Obviously this person has never spent several hours on the 
phone with a drive maker who 'forgot' to put in the documentation that 
TWO jumpers have to be set to put Samsung drives into slave mode :)
Also, just wait 'til the newer IDE cards/drives come out in large numbers
we'll have _big_ fun then...

> Just a little exaggeration, there?  :-)
> 
 [ yet more good SCSI information zzzzapped] 
> 
Basically, the IDE standard was designed for PC compatibles and since there
are so many of them around the IDE drives have become dirt cheap.  However,
SCSI prices have come down _lots_ lately also...
I'd reccomend sticking with SCSI drives for the Apple //.  Don't forget that
with a ramFAST you can also use tape drives, CD roms, etc.  Even though 
there are IDE CD players out there, I seriously doubt that you could get 
drivers for them.
> -- 
> David Empson
> dempson@actrix.gen.nz
> Snail mail: P.O. Box 27-103, Wellington, New Zealand
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