Scor­pio News


October–December 1987 – Volume 1. Issue 4.

Page 24 of 55

A Review of the NE889 Battery “M” Drive

by Derek Beaty.

The Newburn NE899 is a 512K, batten-backed static RAM board, a new board from Newburn Electronics. It’s designed to be upwards compatible with the GM833 RAM-disk board. An important difference is that the boards is battery-backed.

All data files are retained when power is removed & returned. So when you switch on your 80-BUS system, all files arc still intact & ready to run. Has anyone else ever switched off their computer before saving the “M” drive, or is it only me that docs that sort of thing?

The board is designed to accept all future memory ICs using both 28 and 32 pin formats. Whenever the 611024-LP devices are priced down, the board will easily upgraded to 2MBytes.

Being battery-backed, the system tracks be put on the board. Why would you wish to do this when you need a floppy disk to put it there in the first place? Well, for one thing, speed. A system will boot from “M” drive just about immediately. Also, once the system track is on the board, you can take the (physical) disk drives away.

The usual SIMON boot EPROM will not enable a cold-boot without a (physical) disk in drive “A”. Instead, Newburn will update your SIMON boot EPROM to enable this. The boot-up operation checks for a valid system track. If found, it boots from it. If not found, it goes on to boot from (physical) disk, as per usual.

My particular application was a small control system, where cost & dust prevented the use of the usual disk drives. The system had to auto-boot on power-on, or reset. The complete system consisted of a GM813 CPU/​RAM, NE899 RAM-disk, GM816 I/O board, and GM817 PSU, in a MultiNet workstation case. Some additional circuitry was included for input and output buffering. A row of Klippons were mounted on the rear of the workstation case.

The software was written in Turbo Pascal, tested on a disk-based system, and loaded into the NE889 board. The system track was “RAMgenned” onto the NE889 board. This is a program supplied with the boot EPROM to copy a CP/M onto the board. The write-Protect switch was set, the board then removed from the development system and inserted into the “target” workstation.

All worked as expected, including some bugs of my own! The system booted from cold and ran immediately. In fact, you could not see the effects of pressing reset on the system, being so fast.

I forgot that one of the files on the disk needed to be changed at frequent intervals. Write-protecting the board did not allow that. Because the write-protect is also on the edge of the board, I was able to wire a keyswitch to it, so the operator could make changes, as required.

A useful thing would be to mix static RAM and EPROM on the same board. The problem is that the disk directory needs to be write-allowed. Newburn say they are working on something. If more than one board is used in a system, this problem does not arise. One board can contain EPROM, the other static memory. The Gemini BIOS only supports one “M” drive. Fortunately, it is possible to obtain a modified CP/M to support 4 “M” drives. The boards have 2 dil switches to select one of 4 drives. In this CP/M, the “M” are A,​B,​C & D. Using EPROM allow large programs to be stored quite cheaply. The NE889 is available from Newburn without any memory ICs. That enables EPROMs up to 1 MByte per socket (they are 32-Pin) giving a possible 16MBytes of EPROM disk.

Using the standard Gemini BIOS, up to 16 NE889 can be fitted in the system as the same drive “M”. 4 Dil-switches on the board provide address selection. [Ed. - actually, the Gemini BIOSs currently only(!) support up to 2MB of RAM-disk.]

On a Network Workstation, the NE889 provides further benefits. Using the modified Boot, the workstation boots up directly to a “Silicon system” giving 512K of battery-backed files. This allows personal files to be kept off the Fileserver. If the Network is down for any reason, maybe a quick game of Colossus Adventure ?.

If the MultiNet Logos program is kept on “M”, the Network can be booted at any time.

In conclusion, I have found the NE889 board very useful, both in a standard Galaxy, and in a control system. I can’t wait until the larger static memory ICs become available.

Page 24 of 55