80-Bus News

Introduction

A number of storage systems have appeared recently based around the Philips Mini Digital Cassette Recorder (DCR). Priced at less than half the cost of a floppy disk system, they are intended as a cheap(er) alternative to floppies if you want high-speed mass storage.

At the time of writing, there are three such systems available for the Nascom: the ‘Hobbit’ system at £99+VAT, the Grange Electronics ‘CFS’ at £170+, and the MicroSpares ‘HS1N’ system, at £199+ for a single drive system, and £279+ for a double drive system. This is a review of the HS1N double-drive system.

What You Get

I ordered this system last summer (1981) after reading an article on it by the designers in PCW (it was also advertised in PCW), and I sat back and waited for it to come. I waited, and waited, and waited… finally, FOUR MONTHS later, it arrived (now where have I heard that before??) courtesy of the GPO. When I unpacked it, this is what I found:

– Two mini DCR’s
– One ‘NASBUS Compatible’ controller card
– Two leads to connect the drives to the controller card
– Firmware in two 2708’s
– Two 4118’s for workspace
– One mini-cassette
– One manual

One of the connecting leads was twice the length of the other, and was wired up wrong! Luckily no damage resulted from this. The lack of a 77 way edge connector is to be deplored, as some would consider this essential to connecting the controller card to the bus. Rather than wait weeks for them to send me one (or for them to tell me where to go) I got one from my local Nascom dealer.

Hard­ware

The controller card is an 8″x8″ double-sided through-plated fibreglass board, which is just roller-tinned. It would have made a more professional finish if it had been solder masked and silk-screened as well. The board is supposedly ‘NASBUS Compatible’ and seems to conform to the spec. in all but one aspect: the DMA daisy-chain link had been omitted. At first I thought that this was a design/​assembly oversight, but I have since realised that this is to enable entrepid users to fit the DMA chip on the prototyping area of the board, enabling files to be loaded under DMA control… with suitable software, of course. This, of course, wasn’t mentioned in the manual (more of which later). The lack of a link won’t worry those 99.9% of users who’ll never use DMA, and anyway it is the simplest of tasks to add a link should you need it.

All chips on the board are socketed, but none (yes, NONE!!!) are marked on the board. This must give headaches to the poor guy who has to assemble the thing, not to mention anyone who encounters problems, as the circuit diagram supplied is appalling! The controller circuitry occupies about two-thirds of the board, the rest being a prototyping area.

The board I received was very much an ‘Issue 1’ board, with quite a few wire links and broken tracks on it. Some of these links had fallen off when I unpacked the board (due, no doubt, to the solder joints being cut too close to the board) and a bit of detective work was needed to put things right. Just to