Greetings Jimmy Hoffa,
JH>I have something called a "Ramfile" made by a company named
>"Tecall". It has 16 kb batterybackuped RAM, and my question
>is if its possible to expand ram on it? Its very useful, since
>it allows the usage of files similar to autoexec.bas and so.
>The two memory circuits, are of type 6464.
>"JAPAN 8707 HM6264LP-15 UO522YYO"
>The ROM is of kind "HN27128AG-25".
>Please help me with this. :)
An optimistic answer is "Maybe", depending on the Ramfile
hardware and firmware. The likely realistic answer is "No".
The two 6264s are 8k static RAM (SRAM) chips; the 27128 is
a 16k EPROM chip -- for a total of 8k+8k+16k = 32k memory.
The next larger capacity SRAM is the 32k 62256. The physical
difference between the 6264 & 62256 is pin #1; for the 6264
pin #1 is "no connection"; for the 62256, pin #1 is address
line bit 14.
There are 3 potential obstacles to expanding Ramfile memory...
1) Hardware. If the Ramfile designers left the two SRAM pin-1
unconnected, you can't use a 62256 as is; you'd have to do some
soldering-iron surgery to the circuit board.
2) Firmware. If that 27128 EPROM code doesn't know to use any
more than 16k, then adding more memory hardware won't help.
3) Memory map. The MSX uses a banked memory-mapping scheme to
get around the Z-80's 64k limit. Adding memory must take into
account where the new memory will reside, to avoid conflicts
with other memory banks, and then the hardware decoding and
firmware bank-switching routines created accordingly.
Greg_
http://www.netcom.ca/~telic
98.Sept.13, Toronto, Canada.
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