High
Speed Cassette Loader
For
1010, 410, XC11 or Phonemark cassette
Rambit is the Rambo of the cassette based system.
Strong words perhaps, but more than borne out when put to the test.
Just to whet your appetite, I converted two games to the Rambit
format, and booted them. After a very short normal speed boot with
the familiar loading sound, the screen turned black, and a 'loading'
message appeared which was accompanied by rapidly changing
characters along with what I can only describe as the sound of
rushing water. This was the game being loaded into memory. Just 53
seconds later the first game was running. Compare this with the
original, which took 3 minutes 45 seconds! The second game, which
before conversion took 5 minutes 05 seconds to load, was running
just 1 minute after conversion. This game, though, had to be changed
to single load before it could be converted to the Rambit format.
More on this later.
WHAT IS RAMBIT?
What do you get for your £18? The Rambit system
consists of a small circuit board containing an IC and a small
handful of components, and a tape containing the conversion utility
program which is designed to be used either on its own or with an
Assembler/Editor cartridge. You will need this cartridge to assist
in altering multi-stage load tapes to single stage before converting
them to the Rambit format.
The circuit board is easily fitted inside your
cassette unit. There are 5 leads to be soldered to the printed
circuitry, and my 1010 required that a track be cut and a wire link
and capacitor be installed. The instructions give a step-by-step
guide, and a diagram of the tracks is supplied to assist in the
connection of the leads from the interface board. One black mark,
there was no mention of which way round the capacitor should go, but
in fact this does not matter. If you prefer, you can have Rambit
install this board for you. Without this interface converted
programs will not load, and at the moment Rambit will not convert
BASIC programs however the interface in no way interferes with
normal usage of the cassette unit.
So what is the Rambit format? You probably already
know that the normal baud rate for loading Atari tapes is a mere 600
baud whereas most modern machines use 1200 or 2400 baud rates. Tapes
converted to Rambit format all have a short normal speed boot
section at the front of the tape which then controls the loading of
the program itself loading it at the incredible speed of 3300-3600
baud. Rambit's loader program loads into Page 0 and the lower half
of the stack on Page 1 so that most of the computer's memory can be
loaded without fear of overwriting the loader program.
When used in conjunction with an Assembler/Editor
cartridge, Rambit will also save assembled machine code in the
high-speed format. The resulting tape can be booted in just the same
manner as a game, and it will automatically run if you have loaded
RUNAD in your code. You are required to include the binary file
identification bytes, normally automatically included with your
assembled program when saved to tape, so you may prefer to save your
code from the Assembler/Editor directly to tape in the normal
fashion, and then load it back with Rambit for conversion. The
loader program for these binary files loads Page 7 and the lower
half of Page 8, and the appropriate loader is automatically added by
Rambit.
Rambit's function, then, is to save consecutive
areas of memory or single or compound files produced by the
Assembler/Editor cartridge at the 3300-3600 baud rate mentioned.
Single stage load tapes follow Rambit's conventions already, so
converting these is a matter of using the utility's 'L' command to
load the original, and the 'S' command to save the converted program
to a blank tape. A verification facility allows the checking of the
new tape's loading ability. A variety of other commands, many of
which bear a close similarity to those in the Assembler/Editor
cartridge allow one to display and alter memory.
MULTI-STAGE CASSETTES
Multi-stage programs require to be changed to
single stage first. The instructions give a guide as to how to do
this, but basically you have to use the Assembler/Editor cartridge
with the utility to load the first stage in order to locate where
the main section is to be loaded and from where it should be done.
Once this has been accomplished, the main section is loaded with the
'L' command and then you have to add the boot address information to
the start of the program in memory. A study of the instructions
together with a good memory map, such as Compute's 'Mapping the
Atari', and preferably the Atari Technical Notes will be of
assistance here. The standard boot format will allow only 256 blocks
or 32K to be loaded, but Rambit uses the otherwise unused first byte
to allow blocks of over 256 to be loaded, one of the reasons that
multi-stage programs are often used. This block count will be found
in locations $98 and $99 according to length of the program loaded.
Free transfer between the utility and the Assembler cartridge is
possible without problem.
CONCLUSION
Make no mistake, Rambit is a very powerful system
but it requires at least a nodding acquaintance with machine code
and one or other of the two books mentioned to get the best from it.
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