Date   : Wed, 03 Sep 1986 09:18:37-EDT
From   : prindle@nadc.ARPA
Subject: C128 info

Reply to request from singpang%hlerul5.bitnet:

1. The only widely utilized mailing list for the C64/C128 is the USENET list
   called "net.micro.cbm".  This list is *not* gatewayed into the Arpanet.
   I have no idea if there is a USENET/BITNET gateway that passes this list.
   You can *submit* postings to "net.micro.cbm" by sending mail to
   microcomputer.cbm@rutgers.arpa.  However, you cannot receive the postings
   because of the lack of a bidirectional gateway.  Therefore, if you do
   submit a posting that requires a reply, be sure to ask for a carbon-copy
   to be sent directly to your address.

2. There are many communications programs, including Kermit, for the C128 in
   C64 mode.  There are a few (no Kermit) for the C128 in native mode.  There
   are at least 3 (IMP, MEX, and Kermit) for the C128 in CP/M mode.  In short,
   there is no shortage of comm. programs - it's just a matter of finding
   the one you want.  All 3 CP/M programs are in the SIMTEL20 archives (I know,
   BITNET people can't get those yet, but in time.....).

3/4. C64 and C128 disks are virtually identical (there are two flavors, single
   sided and double sided, but with a 1571 drive, either machine can read or
   write either format).  There are currently bugs in the drive ROM which make
   it semi-pointless to use double sided with C64 or C128 mode.  CP/M disk
   formats are simply random accessed variants of the basic C128 double or
   single sided formats - the three possible MFM formats are documented in 
   the (Commodore) C128 Programmer's Reference Manual, and with this knowledge,
   it is not tough reading or writing CP/M disk formats from non-CP/M modes
   (hint: use the U1 and U2 random access functions of the drive DOS).  On the
   other hand, CP/M cannot log in a non-CP/M formatted diskette, so reading or
   writing such from CP/M might be a hassle, if it is possible at all.

5. With the right communication software, a modem works great with the C128
   in any mode at 300 or 1200 baud.  The 128 has no UART, so there is so-called
   "bit-banging" code in both the ROM Kernal and in the CP/M BIOS to support
   receiving and sending bits at the right rate via internal clock interrupts.
   At 1200 baud, this eats up plenty of CPU time, but for general comm. 
   functions (terminal emulation, uploading, downloading, capture buffer), this
   is no problem as long as the remote system can handle an occasional XON/
   XOFF flow control sequence.  I say "with the right communication software"
   because there are bugs in the Kernel ROM, so you cannot use the RS-232 port
   code by the book.  You have your choice of either a TTL/Commodore
   User Port compatible modem (from several manufacturers including Commodore),
   or an ordinary RS-232 modem.  If you use an RS-232 modem, you need level
   converters between the user port and the modem - Commodore and others sell
   such converters, or you can make your own.  I use an Andersen-Jacobson 1259
   RS-232 modem with homebrew (transistor even!) inverters.  I use IMP, MEX,
   and Kermit in CP/M mode, TERM.PLUS, Kermit, XMOBUF, and Punter programs in
   C64 mode.  The only semi-useful program I've used in 128 mode is called
   MicroVT-128 and it has not matured into a stable product yet.

6. C128 CP/M 3.0 is a very faithful implementation of banked CP/M 3.0 with a
   58K TPA.  You should be using the 6DEC85 or 8DEC85 versions to get the
   full benefit of bug fixes, RS-232 port support, and RAM expansion support.
   The only reason *any* CP/M 3.0 program would not run on the 128 would be
   that is was not configurable for the terminal emulation used by the 128
   BIOS, that is an ADM31 (almost).  Many CP/M 2.2 programs will work without
   any problem at all; in this case, any incompatibility (in addition to
   terminal emulation) would be in the form of 2.2/3.0 differences; fortunately,
   these are minimal since 3.0 was designed to be largely compatible with
   2.2, while adding new features.  One example of incompatibility is that
   some 2.2 "unerase" programs are confused by the volume header and/or time
   stamps of 3.0 and thus will not work.  But the vast majority of CP/M 2.2
   products seem to work just fine (try before you buy!).  The 1571 disk drive
   will sense (and cause the BIOS to adapt to) MFM diskettes formatted for the
   Osborn (SSDD), Kaypro II, Kaypro IV, Epson (something or other...), and
   IBM-PC CP/M-86, and possibly some others; consult the manual for details.

Beware, the 128, even in CP/M mode, is not without it's faults.  The Z-80 is
only running at 2Mhz., so don't expect the performance of a 6Mhz. system.  
Screen updates are moderately slow (but not unusable - equivalent to somewhere
around 300 characters/second).  You should set the
baud rate down to 110 whenever you are not using the RS-232 port to minimize
interrupt processing overhead, and maximize *your* use of the CPU.  Diskette
reads (on a 1571 drive) are pleasingly fast (from MFM formatted diskettes), but
writes are quite a bit slower (there is a utility available which almost
doubles
the write speed - much better).  40 column mode is almost useless (sideways
scrolling) for CP/M, so you better use an RGB or monochrome 80 column monitor.
And finally, ROM bugs in the 1571 drive make it nearly useless to try to use
double sided formatted diskettes in the non-CP/M modes (this has been fixed
by Commodore, but it is still not obvious how to get the new ROMS - new ROMS
are being used in newly manufactured units, but it would be hard to say if a
given drive on a dealer's shelf had the old or the new).

Sincerely,
Frank Prindle
Prindle@NADC.arpa