Message-ID: <79@tektools.UUCP>
Date: Wed, 2-Jan-85 14:13:15 EST
Article-I.D.: tektools.79
Posted: Wed Jan  2 14:13:15 1985
Date-Received: Sun, 6-Jan-85 00:10:53 EST
Distribution: net
Organization: Tektronix, Beaverton OR
Lines: 134


   The 1541 FLASH! is a combination of hardware and firmware that
improves the speed of the 1541 disk drive. Program LOADS are over 3
times as fast as standard. Other tasks vary as to how much they are
speeded up, depending on how much the serial bus is slowing them down.
BLITZ!, for example is only about 20 to 25 percent faster. Flash speeds
up data transfer, as well as the actual disk operation. NEW now formats
a diskette in 22 seconds! Other operations are speeded to a lesser
degree. Validate and scratch run about 20-25% faster.

   The package consists of:

   New ROM for the 1541
      It is a 2764 EPROM soldered in a small PC board, which has a
      header soldered to it that plugs into the ROM socket in the 1541
   New Kernal ROM for the C-64
      It is a 2764 EPROM soldered in a small PC board, which has a
      header soldered to it that plugs into the Kernal ROM socket in the
      C64. The PC board also has an empty socket that is for the old
      Kernal ROM. Two wires lead from this board to an external switch.
   PC board that plugs into the user port.
      This board has the switch and connectors mounted on it. It passes
      user port signals to a new user port.
   Five wire cable.
      This cable connects via square pin connectors to the user port
      board, and to the 1541 via eyelet and 2 mini-hooks
   Manual
      This contains installation and operating instructions. Pictures
      before and after installation are included with detailed instructions.

FEATURES:

   The second biggest feature of this package, after disk speed, is the
Kernal enhancements. The cassette routines have been eliminated and the
default device has been changed to 8. A DOS wedge is included. It has
all the standard commands as in the Commodore 'wedge' except the
load/run (up arrow), load (slash), and save (back arrow) commands.
These are omitted because the default device is now 8. New screen
editing commands are included: clear current line; clear to end of
screen; escape from quote or insert modes; cursor to bottom of screen;
cursor to column 16; shift key pauses listing.  The wedge is not
enabled at power up and must be started with a SYS. The screen editing
and fast disk routines are enabled.  The Kernal can be toggled between
fast and standard speed with a poke.  Shift-RUN/STOP does a
LOAD":*",8,1.
   The 1541 ROM has also been enhanced with extra commands. One command
is to toggle between fast mode and standard mode in the 1541. There are
replacement commands for the U1 and U2 disk commands. There is a
command that, when used with a machine language subroutine in the C-64
will load data at up to 10 times normal speed.

INSTALLATION:

   Most of the installation of this kit was simple. The only tough part
is installing the mini-hooks in the 1541. To do this requires lifting a
6522 out of its socket, bending up pin 19 and replacing it in its
socket. Then the 2 mini-hooks are attached to pins 18 and 19. The mini-
hooks are very difficult to get placed so that the case will close. I
feel certain they will be susceptible to coming off if the 1541 is
moved much. I chose to cut off the mini-hooks and solder-tack the wires
directly to the pins of the 6522. The 5 wire cable is routed out of the
case through the fuse holder hole. The eyelet, on the three ground
wires, is connected under a bolt that holds down the corner of the 1541
main PC board. Instructions are included for both the Revision A and B
boards.  I installed in a 1540, which has the same board as a rev A
1541.
   I have heard that a small percentage of C-64s have the Kernal ROM
soldered in, rather than in a socket. If this is the case, it will have
to be unsoldered. Skyles will make the installation for a fee.

EVALUATION:

   The PC boards in this kit are very low quality. This probably
doesn't matter for the 2 ROM replacement boards. It does matter on the
user port board, if the user port is used for other things. The new
user port does not have gold fingers, or polarizing slots. Solder
residue was left on the fingers on my board. The connector does not
have polarizing keys. The switch is a very cheap slide switch that is
very difficult to operate.  The board is mounted to the connector such
that the new user port is half a connectors width above the level of
the original. This leaves anything that is connected to the new user
port hanging in mid air.
   The enhanced kernal is very handy. I wish that both new clear
commands operated from the current cursor position instead of the
beginning of the current line. I miss the up-arrow and slash commands.
Flash speeds up everything at least some. Most things are speeded up a
lot. My C64 is much more responsive now. After using fast mode,
standard speed is almost unbearable.

COMPATIBILITY:

    There are several levels of compatibility available. Most programs
are fully compatible. They work at full flash speed. Some in this
category are BLITZ!, VIDTEX, SYSRES, and nearly all BASIC programs. My
PRINT-MASTER cartridge also works fine. It's DOS works at fast speed,
if I do not SYS up the flash wedge. If full compatibility doesn't work,
you can try slow mode by sending a command to the 1541, and then poking
zero page to put the kernal back in slow mode. If this still doesn't
work you can flip the switch on the user port board to go back to the
old kernal ROM. There is no way to go back to the old 1541 ROM, so
there will be a few programs that won't work at all with flash
installed. One thing that causes problems is programs that call 
subroutines in the kernel or 1541 ROM directly. If they call a routine
that has been modified by flash, they won't work. Another thing that
causes problems is copy protection schemes. Programs with fancy schemes 
sometimes conflict with the modified 1541 ROM. Copys made of these 
programs by automatic copy programs will not work either. Broken copies 
of these programs often DO work, because the copy protect code has been 
removed. In general, programs that use the normal error flagging of 
sectors method of copy protection work with flash.
    I run my 1541 on a switch between my C-64 and my VIC and my AIM, so
it is important that I can still talk to the 1541 with my VIC and AIM.
I can do this if I first use the C64 to send a slow command to the
1541, and then switch to the other computer. The 1541 powers up in fast
mode, but it will accept a 'slow' command in slow mode.  So, it can
still work with the VIC even if the modified C64 is not around. By
flipping the switch on the user port board I can use the C64 with an
unmodified 1541.

HOW IT WORKS:

   Flash uses the shift register in the C64's 6526 CIA connected to the
shift register in the 1541's 6522 VIA to transfer data. Pins 6 and 7 of
the user port are connected to pins 18 1nd 19 of the VIA. One wire is
for data and one for timing. This takes advantage of unused circuitry
on both the C64 and the 1541. Why didn't Commodore do it this way in
the first place?

Joel Swank
Software Center Tools Support
50-487
Tektronix
Beaverton OR 97077
(503) 627-4403