Re: Some upgrading questions...

[dempson@atlantis.actrix.gen.nz (David Empson)]

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.

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?

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.

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.)

> The only time I would recommend someone use scsi is if they require a hd 
> bigger than 540mb, since the drives which work with ide >540mb are er, 
> rather tricky to configure at the best of times.

This is mainly a limitation of the AT BIOS (and most subsequent
BIOSes, which are based on it).  The AT BIOS is limted to a drive with
1024 cylinders, 16 heads and 64 sectors per track, which works out to
512 MB.

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).

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

> But, especially for beginners, ide is certainly easier, since it's 
> plug-in-and-go as compared to the almighty amount of stuffing around 
> which seems to go on with apple scsi drives.

Eh?  I have had three SCSI drives (an old Rodime, a SyQuest and a
Quantum).  I have had _NO_ problems with them (other than one drive
going faulty after several years).  In all cases, I plugged them in and
they worked.

There are often problems with termination and supply of termination
power.  The RAMFast rarely suffers from this problem.  If you get a
drive which supplies terminator power (like my Quantum LPS240), you
are unlikely to have problems with an Apple SCSI card either.

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?

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)?

> With ide you don't need to worry about terminators, or thirty-seven-thousand
> different submodels of the same card.

Just a little exaggeration, there?  :-)

There are two versions of the Apple SCSI card.  The original one has
three ROM releases, of which only the latest (revision C) should be
used.  The High-Speed SCSI card was modified to add termination power,
but has never had (or needed) a ROM upgrade.

The RAMFast has two versions (Revision C, which works in a IIe or IIgs
and has 256k of cache RAM, and Revision D, which only works in a IIgs
and has 256k to 1MB of cache RAM).  The RAMFast certainly went through
countless ROM revisions, but has settled down now.


-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand