80-Bus News

speed character update to the screen display is required. Something like Naspen (or Diskpen) could not be made to work as it updates the whole screen content every time a key press is made (in the Insert mode). Without a radical redesign, ‘Pen’ would refresh the whole screen far too slowly to be practical. Maybe this is an argument for redesigning ‘PEN’, but that’s a different story.

The other penalty is the RAM overhead used by the character generation software. It uses 1K of bit patterns for the characters and another 1K of user definable bit patterns for the user defined character set. That’s 2K for starters. Another 2.5K is used for the ‘getting and putting’ of the character bit patterns and to make the AVC behave sensibly as a display device. In fact it’s configured to look a bit like a Lear-Siegler ADM-3A terminal, a definite plus point. It’s all quite clever, and they’ve crammed quite a lot into the 2.5K of control software. However, it’s 4.5K of RAM space and the Nascom with its 48K RAM card (unless you have two RAM boards, or Gemini’s 64K job) is not over generous when it comes to running CP/M type disk systems. Perhaps Nascom could supply the software package in EPROM to reside above the top of user RAM, the CP/M BIOS ‘hooking’ into the EPROM package. This would not increase the BIOS size (in fact it could make the BIOS smaller), but then if it’s in EPROM, where’s the RAM for the user defined character set. No doubt Mike Hessey and his lads have worked their way round that one.

To prove the point that the card could be made to perform adequately in a business type environment that old faithful Wordstar was demonstrated, and it worked well. Noticeably slower on scrolling and repositioning text than the Gemini IVC (but then the Gemini IVC works differently and doesn’t have colour), but anyone used to seeing Wordstar on a terminal being driven by something like a DEC-10 would be immediately convinced of the speed at which the AVC could be made to perform. Sadly it left me cold. Nothing to do with the AVC, it’s simply that I consider Wordstar as being one of the most unnecessarily complex and frustrating lumps of software around (wait for the defensive letters to come pouring in after that comment).

As mentioned earlier, there are options that can be supplied for the AVC. As standard the PAL encoder is not fitted, although that should not be expensive, a tenner or so I would think. Enough software is supplied to make it work in either colour graphic or alphanumeric mode, but an enhanced software package will be available to enable things like the rotation of solid objects and some sort of picture ‘zooming’. The standard software seems to link into Nas-sys with minimal difficulty, probably by using the ‘U’ command functions.

So to sum up on first impressions. It’s good, and at about £155.00, not too expensive for the sort of market where most Nascom’s are used. It’s speed is not overly impressive so don’t think you can do high speed animation with it. (For those who saw the Horizon programme on computer graphics, don’t forget that ‘Carla’s Island” used the whole resources of the Cray One computer, and could still only run at one frame in eight seconds; and that “Teapot” required several million pounds worth of DECs working in parallel and many tens of man-years of software development.) Within it’s limitations (which aren’t many from the point of view of the potential users) it performs well and achieves its original aims entirely. (By the way, the rumours were true … the AVC is 10″ x 8″.)

To change the subject, we owe our apologies to Nascom. In the last two issues we could have created the impression that the Nascom FDC card was simply the pre-receivership Nascom FDC card put into production. Nascom tell us that this is not the case, and that the card is a redesign and several significant design changes have been made. Also, arising from the last issue, Nascom would like to point out that the Nascom disk system is now available with the TEAC FD-50F drives giving some 700K of formatted space per drive, and that judging from advertised prices, the price advantage still lies with Nascom rather than Cumana as was implied. Lastly, our overview of disks systems should have drawn a distinction between DCS-DOS, DCS-DOS2 and NAS-DOS. NAS-DOS and DCS-DOS2 are related and both contain enhancements over the original DCS-DOS. Our apologies to Nascom and Dove Computing Services for these inaccuracies.