Hi Artie,
       Your doing it again !

Jan issue of CN you made at least three *unnecesary* references to
computers other than the C64/128.

If I wish to read about these machines I'll buy/subscribe to the
relevent mags.

Also  (not a criticism, but simply to enlighten you)
The Swiftlink cartridge is NOT "the best of the RS232 interfaces",
although it is probably the most well known of the UART cartridges.

The differences between an RS232 cartridge and the UART cartridges are
several (as are the prices).

Firstly, an RS232 cartridge is designed to take the C64/128's RS232
signals and convert the 0 - 5v signal levels to the "true" RS232
standard of +-12 volts. This is *all* it does, and for speeds of 2400bps
or less this is all that is required (9600 for the C128).

To purchase a UART cartridge if you are running these speeds is
literally throwing money away.

The Swiftlink is a different kettle of fish altogether.. this is a true
UART (Universal Asynchronous Reciever Transmitter). It uses a 6551 ACIA
(Asynchronous Communication Interface Adapter), and has its own crystal
oscillator. Rather than being an "interface" to convert voltage
levels it is a "stand alone" type device in its own right.
To use this device on the C64/128 requires the use of specially written
software.  (for this reason alone they are *not* the best choice for
CBM users, which is what you stated in CN)

Of the dozens of comms programs available for the C64/128 only 3 or 4
of them support the swiftlink device.

*All* of the comms programs will work with an RS232 interface though.

The confusion arises because the Swiftlink is often advertised as "an
RS232 INTERFACE" where in reality it is an RS232 DEVICE DRIVER that
happens to plug into the C64.

I dunno if I've made myself perfectly clear, so lets try to explain it
another way.

What is a modem ?  Most people consider this as a DEVICE in its own
right. (which it is).  However it can also be considered as an
INTERFACE between a computer and the phone lines (which is also true).

So what we have is:

  ----------- raw    -------------  RS232   ---------- modultd---------
 | computer |----->-|  RS232      | ----->--| modem  |----->--| phone |
 |(not C64) | data  |  driver card|  Data   |        |  data  |       |
  -----------        -------------          ----------        ---------
   Device.            (internal             interface/         device.
                       add on)              device


The computer *addresses* the driver card, which in turn sends RS232
signals to the MODEM, which converts the RS232 DATA to a modulated
signal for phone transmition.


Then we come to the C64/128  using a "normal" interface


 -----------          ------------- amplified--------- modltd ---------
| computer |------>--|  Voltage   | ------>-| modem  |------>-| phone |
|  C64     |  rs232  |  converter | rs232   |        | data   |       |
 -----------  data    -------------   data  ----------        ---------
  Device.              Interface            interface/         device.
                                             device


Please note the ABSENCE of the RS232 driver card - The C64 doesn't
*need* this. It generates its OWN RS232 signals that simply need a
*voltage* conversion to drive the modem.


And now with a Swiftlink cartridge:

-----------         ---------------  RS232   ---------- modltd ---------
| computer |---->--|  RS232 device | --------| modem  |--------| phone |
|  C64     | raw   |  driver       |  data   |        |  data  |       |
-----------  data   ---------------          ----------        ---------
 Device.            Interface/              interface/         device.
                      device.                 device


Which looks remarkebly like the non CBMers set up :-)

The main thing to note is the DATA being sent from the computer..
On non CBM platforms this is always raw data that needs to be converted
to RS232 format.

The C64 will Generate RS232 data with no additional help (only the
voltage levels being "low").

When a Swiftlink is used then the internal RS232 routines are NOT used
at all. Raw data is sent to a DEVICE driver - the same as non CBM
machines. This is why special software must be used.

Simple really isn't it ?

So why to C64ers "panic" when it is mentioned that they need an
"interface" to drive a modem ?  I dunno because the reality is they
don't even need one.
In fact (although not recommended) MOST modems will work quite well on
the C64 without any form of "interface" at all - these modems are quite
happy with the C64's  0-5v signal levels.
(If you don't believe me, try it)

I never see Beemers screaming "all to hard" because they NEED a driver
card to use a modem (or joystick for that matter), and so am at a real
loss when C64ers find it such a dilemma.
(Possibly because most Beemers are computer illiterate and they buy the
RS232 card already installed "as standard", so they are unaware of this
fact).

Maybe the C64 designers should've made it hard for us by NOT including
RS232 capability as part of our operating system.
This way we wouldn't have to "panic" when we find that their forethought
would cause such mass confusion over such a minor thing as non-standard
voltage levels.

Anyway, back to the point - An RS232 voltage converter (commonly called
an RS232 interface) is NOT the same as an RS232 Device driver (also
called an RS232 interface on CBM systems, but called an RS232 driver
card on other platforms).
The Swiftlink is a device driver.

Well, I dunno if I've made that any clearer or not (no matter how I try
to explain it there is still someone scratching thier heads).

The bottom line is that UNLESS a C64er wishes to go faster than 2400
(9600 for C128) then buying the Swiftlink device driver is NOT the way
to go because it doesn't give any benefits whatsoever, and worse still
it does need special software 'cos it does not (cannot) use the
internal RS232 routines that we have been blessed with for all these
years.

Our only shortcoming is that the internal RS232 of the C64 cannot
handle the high speed modems. (but 10 years ago when the C64 was made
these modems were as rare and expensive as the proverbial rocking horse
sh*t and hens teeth). We are still one up on other computer users
though where add-ons are *required* for *any* speed modem.

As many have said.. the C64 may be getting long in the tooth, but it
was years ahead of its time.

Cheers
Rod
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