Review of the NE898 processor board
by Peter Bell
“Review of the what board?” I hear you ask. A year ago, in Volume 1, Issue 4 of
Scorpio News, you may remember seeing reports of two new 80-BUS processors,
both with Gemini part numbers – the GM880, based on the Hitachi 64180, and the
GM890, using the Zilog Z280. Both of these boards appealed to me since my interest
lies in developing the operating system software – just think what could be done
with the increased memory, DMA and more interrupt facilities.
It didn’t take long to decide that the Z280 based board, although possibly less
‘compatible’, would provide the greater challenge with its dual supervisor/user
modes, separate instruction and data space and exception trapping. I rang Gemini
to enquire about availability. After a pause the receptionist said “There’s no one
here at the moment. Ill get someone to call you back.” My call still hasn’t been
returned, eleven months later! By the next day I decided to phone Newburn, whose
advert in the same magazine offered the GM890 at a special introductory price.
‘Two weeks’ the man said. It seemed that the GM890 development was being carried
out as a joint exercise between Newburn and Gemini, with Newburn primarily
responsible for the hardware.
Being an impetuous person I sent an order with a deposit cheque. Over the weeks
that passed I had several conversations with the people at Newburn. They were
always willing to spend time detailing the various problems they were experiencing
inthe development of the GM890, but delivery was always ‘a few weeks away’.
In June this year I received a letter advising that development of the GM890 had
been discontinued, but that an alternative board , the NE898, was almost ready, with
a price tag of £439, This time they had opted for the 64180. chip, now also supplied
by Zilog as the Z180. Apparently the Z280 is not fully compatible with Z80
peripherals using the mode 2 vectored interrupts, and this is what caused the
development to be abandoned. Disappointed by this news I took a little time to
decide to try the NE898. However, I have now been using this board for just one
week, and am very impressed. Obviously this device is in almost direct competition
with Gemini’s own product. Anyway, let me list some of the features and facilities
that the NE898 offers:–