Re: Apple //c smartport compact flash adapter

[mdj <mdj.mdj@gmail.com>]

On Feb 5, 5:03 pm, Robert Justice <rjust...@internode.on.net> wrote:
> I ran some tests to see how the speed compared to all of this theory.
> I created a basic program with 10 bload test,A$4000,L$4000, so 10 x
> 16K of data. This took  10.6 - 10.9 seconds. so my calculations make
> this about 15KBytes/s. Not that fast, but its a start. This time was
> from hitting the enter on the run, until the prompt came back.  It
> took 28.3s for writing, so this was considerably slower. I'll have to
> have a look why this is so much slower. The internal floppy took 29.5
> for reading, and 148 for writing.

That's about 75% of what you could reasonably expect for read speed,
so depending on buffering/handshaking between your smartport code and
the IDE bit banging to run the CF card you might be able to get a bit
more, or perhaps not. Do you have enough RAM on the uC to do a couple
of blocks of read-ahead? That might be a speed win. The write speed is
so much slower that it almost has to be somewhere in the IDE code ...

> Its interesting that smartport devices where only ever connected to
> cards with the IWM on them. Looking at the original disk ii interface,
> I don't see why this would not have supported smartport devices, as
> they only use the normal timing as per a disk II drive. I suppose they
> just used the iwm with the liron, as it needed to be a new card
> because of the firmware rom to run the smartport,

I've wondered that myself. A firmware card seems all that is required,
but perhaps there's fanout issues with the original Disk ][ controller
circuitry and they were worried about signal drive strength with
duodisks hanging off a chain of two unidisk 3.5's.

Then again, the Liron cards would have cost nothing to make in
quantity, and probably made it easier to justify the high price they
had at the time.

> Also, i wonder why they have not used the 2x mode available on the
> iwm? Although, looking at the code in the iic, it does a good job of
> decoding the packet as it comes in. If it where to run the interface
> at double speed, then it would probably have to concentrate on reading
> the data, and then decode it later. ( if it can read it fast enough)

2x mode is used for 3.5" drives, and if the Apple II was fast enough
to do it, you wouldn't need SmartPort at all :-) Of course the IIgs
does this, as does the IIc plus, which incidentally has a 2k RAM
buffer added for precisely this reason - it simply can't decode the
data on the fly at 1Mhz.

Apple made a hard drive for the Mac back in the day (HD20) that
probably used that mode, but that idea was discarded in favour of SCSI
across both Apple II and Mac lines. The data payloads of GUI
environments really did dictate faster IO solutions.

Matt