Benoit, 25-10-94
From: IN%"msx@stack.urc.TUE.NL" 25-OCT-1994 09:13:53.62
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Subj: RE: Turbo R RAM up grade
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Date: Tue, 25 Oct 1994 08:51:31 +0100
From: benoi1@world-net.sct.fr (BENOIT)
Subject: RE: Turbo R RAM up grade
To: msx@stack.urc.TUE.NL (MSX mailinglist)
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>I read your message about Turbo R info in the MSX mailinglist. (It was
>forwarded by Wiebe Weikamp.)
>The function of port E9 is in the textfile below. About the ports EC, EE and
>EF, (among others) I don't know what they do exactly but I've seen they were
>used in the ASM-listing of a MIDI-player.
Thanks for this textfile! now I understand what is the use of E9, EC, EE, EF :-)
>What you said about ports E4/E5 I didn't understand. I made up from it, that
>you think the MSX Turbo R has 1 MB DRAM internally? I doubt this VERY much.
>But I guess I misunderstood what you wrote.
Well, sorry if my English is not as good as I would like it to be, but
translating technical French (I mean electronic words etc..) is not very
easy for me ;-) anyway I did not say that Turbo R GT have 1Mb internaly, I
only said that it can have it with out to much hardware modification, I get
this information from Japanese textfile (so writen in KANJI :-( , here is
some info I did understood because they were writen in (ROMANJI = ROMAN
charset and also because I have the schematic diagram of the Turbo R GT )
Between the S1990 and R800 there are three signals: A15, A14, A12. Those
signal are tied (connected) to a "diode" (<- French word;-) named D301 via
resistors (R352 (A15), R353 not connect (A14), R354 (A12)). Here is the
meanning
of those bits:
S1990 A15 A14 A12
L L L 64Kbyte
L L H 128Kbyte
L H H 256Kbyte(ST)
L H L 512Kbyte(GT)
H L - 1Mbyte ( see note 1)
R800 A15 A14
L L 64Kb * 4 (bits)
L H 256K * 4bits (ST/GT)
H L 1M * 4bits ( see note 1)
H H 4M * 4 bits
NOTE 1: there was KANJI in this place and do not understand them :-( since
that was the same KANJI, I think that it was to say that they will use this
configuration for the RAM upgrade ?
For the memory upgrade on the Turbo R GT, you "only" have to move R352 to
the R353 place to make A15 become H and A14 becom L (H is High and L is Low
in logical electronic ;-) see table above for more information, those
resistor are under the S1990 (solder side). Fill the J302 near the R800
(coponents side) this jumpper is the MA19 address bit normaly it is not
connect between S1990 and R800. Replace the 4 DRAM chips 44256 by new one:
514400 (90ns maximim) if you can find one ;-) because even in Japan there no
more of them :-( I know it because a friend of mine study Japanes in Japan!
But you can use aSIMM bar of 1Mbyte for PC or ATARI & MAC (apple ;-) but you
will have to make a PCB (Printed Circuit Board;-) if you want I have draw
one using EAGLE layout editor I can send you the file if you want?
Well, now you can close you MSX Tr GT and switch it on to see: MAIN RAM
1024Kb!. But those 1024Kb only seem to work under DOS 2! under Basic or if a
program use Memman, it dos not work! I have use an utility mapper tester
from Digital KC (I get it when I bought my external 2Mb mapper), so when I
run this utility it says (in Dutch! :-( I do not understant it!!!!!!!!) (I
think it say that ;-) that I found 6 bits for the mapper (00PPPPPP where P
is the page number on 6 bits! so 64 pages ;-) but only 5 of them are
available! so only 512Kb can be use and not 1024Kb! and when I use ALLOCATE
USER SEGMENT fonction of the DOS2, it seem to work!
That's all, I hope you will understand, if your are interesting in, I can
send you all the files I have about it? using normal mail, here is my
"normal mail" address:
BENOIT Martial
36, av Maurice Gallais
93150 Blanc Mesnil
FRANCE
Greets from FRANCE
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