On 10/03/2011 23:24, Lee Privett wrote:
Of the three large chips, one is an EPROM 2764(middle), the one below
is an 8059 or WD1770
That'll be the disk controler, WD1770, I suspect the 8059 is a date
code. Odd that it's only got a 2764 (8K) eprom, most of the QL
innterfaces had either a 27128 (16K) or 27256 (32K).
and the largest chip is marked as a 4500A. The
Numm not heard of that one does it have any other markings ?
memory chips are M5K4164 and I suppose that filling the other 8 empty
How many memory chips are fitted currently ? 4164s are 64K x 1bit, so a
group of 8 gives you 64Kbytes of ram. If there are only 16 RAM sockets
and you filled them with 2764s that would give an extra 128K total.
It may be of course that you can populate them with 41256 which are
pinout compatible (apart from having an additional address line on pin
1), to give two banks of 256K for a total of 512k expansion, but that
would depend on the other logic on the board.
Cheers,
Phill.
--
Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !
"You can twist perceptions, but reality won't budge" -- Rush.
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