Rambit

Review by Derryck Croker

 

Issue 24

Nov/Dec 86

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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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