The disc interface was one of the earliest expansions promised by both Newbury and Grundy, since it was the one extension which differentiated the Newbrain from it's closest competitors, e.g the Spectrum. From the beginning the Newbrain was intended to be integrated into a CPM environment. CPM from Digital Research was the main Disc Operating system for 8 bit computers and was seen as an essential component for the commercial success of the Newbrain. It enabled the the creation of a small, integrated and dedicated turn key system for a major chemist/pharmacist firm. The interface was built into a cream box, the same size, shape and colour as the Newbrain it'self, and was designed to fit below the Newbrain as part of a stack, including the Expansion, mainly memory, interface. I have not seen an expansion interface for sale, but recently I managed to purchase on eBay a disc interface, unfortunately out of it's case, see below. Very few of these were produced in the UK, but Tradercom in Holland realised their significance and produced them in quantity. As a result there is a wealth of Disc related software, inc CPM itself, available in the
online archive of the
"De HCC Newbrain gebruikersgroep"
From the markings on the board, this is Grundy part number NB 12145/A/3. It is obvious that this was anything but a completed design, as there are numerous production, but hand done alterations to this board. Extensive areas of thin black wiring, additional resistors and capacitors, all show that a lot of expensive hand alterations had to be made, to make these units work, no wonder that Grundy went bust!! The board is very complex, you have a feeling of
Dejavu, as it looks very like original Newbrain main board. Well it might, as it is in fact a dedicated micro controller, with Z80, ROM and RAM. Looking to the far right of the board, the two identical chips, immediately to the left of the central indent are 2114s which together make up 2k of 8 bit RAM, there follows, the first 64K EPROM with it's white label, then the very black Mostek Z80, followed by the second EPROM and finally the D765 NEC floppy disc controller chip.
The design is intended to fit in at least the base of a standard Newbrain case, with only a new top. The connectors along the back, fit a modified aluminium core sheet from the Newbrain, which again acts as a heat sink to a power transistor for voltage regulation. From left to right they are the standard, locking disc connector, two paired expansion connectors one in an identical position to the Newbrain, the other directly behind it, with a cable fitted in it, and finally two Newbrain style power connectors, OUT and IN. The latter utilises a standard Newbrain power supply.
The controller is flexible and allows single and double sided, normal and high density recording and 40 and 80 tracks. All all of these can be set up, depending upon your configuration in a CPM Config file. That said, the standard Newbrain was not really well equipped for CPM, which demanded a full 64k, rather than the 32k in the normal configuration. This made an expansion unit with at least 64k an essential extra. Very short sighted, as it would have been easy to produced a 64k card to replace the original. As a result there is a lot of software in the Nebrain GG archive which is for a 96k Newbrain, 32 in the machine 64 in the espansion unit. You needed the latter for much commercial software, such as dBase II and Wordstar.
