Review of the 32K CMOS Battery-backed RAM Board.

A beautiful piece of work was the first thought that case to mind after seeing this board for the first time a couple of weeks ago. A battery-backed RAM board was one of those things that I used to dream about months ago when the cost was way out of my range. Now, a fully populated board (32k) is available from Microcode (Control) Ltd. for £185 (+ VAT) and well within the price range of all but the most miserly Nascom and Gemini micro owners.

The board arrived well packaged up in acres of corregated card board. The board that I was provided with to review was the fully populated one but it is possible to buy the board populated to 2k or 16K and then add additional 6116s as required (or can be afforded). The board is also available unpopulated but for the price it is hardly worth the hassle of construction which makes the 2k board a better bet.

I am not sure if everybody gets an appropriate piece of wire with which to make up all the link connections that are necessary to configure the board but I did which saved me the hours it would normally have taken me to hunt through our scrap box to find a suitable replacement. Depending on how nimble one is with ones fingers, a piece of wire between 24 inches and 4 foot would be required to completely configure a fully populated board.

The board itself is double-sided, through hole plated, solder resisted and silk-screen printed. It has nice, easy-to-follow tracks and is nicley laid out. The chip numbering (IC numbering) is of the format that that Nascom constructors have grown to love, totally haphazard. The unusual point about the board is that the components are orientated in the opposite direction to the printing and numbering on the board which could cause some confusion. This was evidently due, so I have been told, to the fact that when the board was originally designed, the machine it was designed for had all its boards in upside down, so, to make fault-finding easier in-situ the board was labelled in such a way that the labelling was the right way up then the board was upside down. A minor point really but sure to confuse some constructors who choose to build up the bare board.

There are 5 different link blocks to wire up which configure the board in one of many ways.

Link Block A (LKSA)     Address boundary option.

This link block is used to select where in the memory map the RAM is to sit. The RAM chips themselves are configured in 4K blocks and each of these blocks can be connected to any of the 16 block decode pins. More than one block of RAM can be connected to the same decode block which then leaves the final decoding tu the Page control links. The decode linking is