164485913@excalibur.UUCP (02/05/87)
Greetings Netlandians,
I have a small problem/question about the Leading Edge model D (PC clone).
This computer comes with 512K of RAM and 9 sockets for 256K-bit RAM chips
to increase the memory to 640K of RAM.
According to various sources (my calculator included) 512K + 256K is not
640K, but 768K.
What I would like to know is:
Where did the other 128K of RAM go?
Can this RAM be used as a RAM-disk, and how?
(I doubt that MS-DOS can use it since it's above 640K.)
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=======================================================================andy@thelink.UUCP (02/06/87)
Re: Memory in Leading Edge D's.
About 4 months ago, Leading Edge changed their board design to use
all 41256 RAMs. Previously it came with two rows of 4164's, with
two empty rows that you could stuff. Now it comes with two rows
of 41256's with room for another row. Yes, this is 768K. Can you
access it? Yes and no. The next 64K above 640K is unused, unless
you have EGA. There was a small assembly language program published
in the Byte IBM PC issue November 1986 that would tell the BIOS you
had 704K of RAM, initialize the extra RAM, and reboot. I have not
actually tried this program, but it's something to try. The other
64K of RAM is most likely mapped out, since this is where CGA and
MGA RAM start.
Andy Dustman ({ihnp!alpha,iuvax!ndmath}!ack!andy)
Computer Specialistsberger@clio.UUCP (02/07/87)
Typically (and I'm not familiar with your machine, so it may not apply) the address decoding expects two banks of 256K ram and one bank of 64K ram for a total of 640K. In some machines, you can actually install 768K, but that will usually conflict with devices that may be memory mapped above 640K, like the standard IBM type display controllers.