DRAGON will offer 64K upgrade for the Dragon at the same time as the disc drives are launched in late May.
The upgrade will cost in the region of £70 and will take the form of a board-swap of the main printed-circuit board. This will be undertaken either by Dragon themselves or by a number of selected Dragon service agents.
The reason for the upgrade is that when discs are added to the Dragon 32, followed by loading in the 0S9 operating system and perhaps another language from disc, there is little user Ram left in which to write programs.
The 64K version has the disadvantage that, because of the chip combination used in the Dragon 32, the 16K Microsoft Basic in Rom overwrites 16K of Ram. The way the Dragon’s memory map is arranged means that the 16K overwritten is the third quarter of the 64K Ram. What this means is that there is still only 32K of Ram addressable from the Basic — the remaining 16K above the Basic can be used to store machine-code.
“The 64K board really comes into its own when used in conjunction with the 0S9 operating system and discs,” explained Dragon’s marketing manager, Richard Wadman. “The 64K can then be used in several ways. You can use the 0S9 operating system to switch out the Microsoft Basic in Rom giving you a clear 64K soft machine. Then you can load into the 64K from disc any operating system you like — Pascal, Lisp, C and so on.
“Alternatively, because of the way the 6809 and SAM chips in the Dragon are configured, you can copy the 16K Microsoft Basic into a sensible position in the Ram giving you an uninterrupted 48K of user Ram addressable in Basic.
“Obviously the 64K board-swap is of less use if you don’t have discs, but you can store machine-code subroutines in the top 16K and then call them for use in a 32K Basic program.
“Also, when you buy the 64K upgrade it will be supplied together with a cassette which will contain the software necessary to switch out the Basic Rom, giving you a 64K of machine and also to move the Microsoft out of Rom and into Ram, giving you 48K addressable by the Basic.”