Re: Apple //c smartport compact flash adapter

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

Toinet <antoine.vignau@laposte.net> wrote:

> Hi Robert,
> I own a IIc that I was about to sell and I have to admit that your
> message makes me wonder whether it would be the good thing to do.
> Nevertheless, thank you for that and keep up the good work.

A Smartport CF/SD adapter will certainly make a //c more useful by
giving it access to greater storage space (without having to resort to
rare SmartPort/SCSI adapters), but it won't be a speed demon.

I'd expect this adapter to be somewhat faster than a 5.25" drive or
UniDisk 3.5, due to elimination of rotational and seek latency,
buffering and IWM switching delays in the UniDisk 3.5, and 7-and-1
instead of 6-and-2 encoding in comparison to a 5.25" drive.

The raw data transfer rate of SmartPort is the same as the UniDisk 3.5:
theoretical limit is 7 bits every 32 microseconds, thus 27 kilobytes per
second, but there will be delays due to SmartPort protocol overhead,
which reduces the limit further (perhaps 25 KB/s is achievable).

A card in a slotted 1 MHz Apple II using a software loop can go somewhat
faster than that, an accelerated 8-bit Apple II (or any IIgs) could be
somewhat faster again (with the right drivers), and DMA-based cards can
go a lot faster.

The 3.5" drive in an Apple //c+, or an Apple 3.5 Drive on a //c+, IIgs,
or IIe with a SuperDrive card is about twice as fast as SmartPort (but
with seek and rotational latency), and a SuperDrive on a SuperDrive card
can be up to four times faster than SmartPort for reading.

Still, higher capacity than a floppy is a big plus.

-- 
David Empson
dempson@actrix.gen.nz