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HRDMMRY.ARK
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2006-10-19
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HORIZON RAMDISK 256K EXPANSION PROJECT
by EDWARD A. HALLETT
SOUTHWEST NINETY-NINERS
Edited by Kevin Kapus, Front Range
99ers, for use with HORIZON SOURCE CODE
VER_04
The HORIZON RAMDISK is available in 90K
SSSD (360 SECTOR) and 180K DSSD (720
SECTOR) sizes. This project expands
the size to 256K (976 SECTORS) for an
increase in storage capacity of 64K
(256 SECTORS) or 35.5%.
This increase is accomplished by adding
one 74LS154 (4 to 16 DECODER), one
74LS02 (NOR GATE), and eight 8K
6264LP-15 STATIC RAM chips, removing
one 74LS138 (3 to 8 DECODER) chip, and
modifying the DSR CODE to recognize the
existance of the added memory. The
original HORIZON RAMDISK CIRCUIT does
not fully decode one of the five memory
address lines from U9 limiting it to
180 K. By fully decoding this line we
pick up eight more CHIP SELECT SIGNALS
bringing us up to 256K (976 SECTORS).
This utilizes the original design to
its fullest potential with only a few
SIMPLE MODIFICATIONS.
:::::::::::::::::::::::::::::::::::::::
CAUTION: THIS MODIFICATION IS
UNDERTAKEN AT YOUR OWN RISK
AND MAY VOID YOUR HORIZON WARRANTY
:::::::::::::::::::::::::::::::::::::::
CAUTION: REMOVE THE NICAD BATTERIES
FROM THE RAMDISK BEFORE STARTING.
USE CARE WHEN HANDLING THE RAM CHIPS TO
AVOID DAMAGE FROM STATIC.
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
1. Remove U1, the original 3 TO 8
DECODER CHIP, from its socket an
DISCARD.
2. Remove the EIGHT PIGGYBACKED PAIRS
of 8K RAM CHIPS from their sockets
U3-U6 and U12-U16.
3. Remove U2, the original 4 TO 16
DECODER, from its socket.
4. Remove U10, the original NOR GATE,
from its socket.
5. Install a THIRD ADDITIONAL 8K RAM
CHIP PIGGYBACKED on top of the removed
PIGGYBACKED PAIRS of 8K RAM CHIPS
connecting EACH PIN to its
CORRESPONDING PIN below with the
EXCEPTION of PIN 20 (CHIP SELECT).
BEND PIN 20 outward like PIN 20 on the
CHIP below it. Reinstall these EIGHT
PIGGYBACKED TRIOS into their sockets
(U3-U6 and U12-U13) and RECONNECT the
ORIGINAL lines from PIN 20 of the
CENTER CHIPS to their ORIGINAL POINT on
the EXPANSION JACK next to U3.
6. Install the ADDITIONAL 4 TO 16
DECODER CHIP (74LS154) PIGGYBACKED on
top of the ORIGINAL 4 TO 16 DECODER
CHIP, U2. Connect PIN 12 and PINS 20
THRU 24 to their corresponding PINS
below. Bend PINS 1 THRU 11 and PINS 13
THRU 19 OUTWARD. Reinstall the
PIGGYBACK PAIR of 4 TO 16 DECODERS in
its U2 socket. Connect lines from the
UPPER CHIP PINS 1 THRU 8 as follows.
PIN 1 TO U1 SOCKET PIN 15.
PIN 2 TO U1 SOCKET PIN 14.
PIN 3 TO U1 SOCKET PIN 13.
PIN 4 TO U1 SOCKET PIN 12.
PIN 5 TO U1 SOCKET PIN 11.
PIN 6 TO U1 SOCKET PIN 10.
PIN 7 TO U1 SOCKET PIN 9.
PIN 8 TO U1 SOCKET PIN 7.
These provide the CHIP SELECT SIGNALS
to the ORIGINAL (CENTER LAYER) of 8K
RAM CHIPS.
Connect lines from the UPPER CHIP PINS
9 THRU 11 and 13 THRU 17 as follows.
PIN 9 TO PIN 20 U3 TOP 8K CHIP.
PIN 10 TO PIN 20 U4 TOP 8K CHIP.
PIN 11 TO PIN 20 U5 TOP 8K CHIP.
PIN 13 TO PIN 20 U6 TOP 8K CHIP.
PIN 14 TO PIN 20 U12 TOP 8K CHIP.
PIN 15 TO PIN 20 U13 TOP 8K CHIP.
PIN 16 TO PIN 20 U14 TOP 8K CHIP.
PIN 17 TO PIN 20 U15 TOP 8K CHIP.
These provide the CHIP SELECT SIGNALS
to the ADDITIONAL EIGHT 8K RAM CHIPS
(TOP LAYER)
7. Install a new NOR GATE (74LS02)
PIGGYBACKED on top of the ORIGINAL NOR
GATE, U10. Connect PINS 2, 7, and 14
to the CORRESPONDING PINS below. BEND
PINS 1, 3 THRU 6, and 8 THRU 13
outward. Reinstall the PIGGYBACKED
PAIR or NOR GATES in its U10 socket.
Connect LINES from the UPPER CHIP as
follows.
PIN 1 TO PINS 18 AND 19 U2 UPPER CHIP.
PIN 3 TO U1 SOCKET PIN 6.
These provide the CHIP SELECT SIGNAL
for U2 UPPER 4 TO 16 DECODER CHIP thus
fully decoding the available MEMORY
ADDRESS LINES.
PINS 4 THRU 6 and PINS 8 THRU 13 of the
UPPER NOR GATE U10 are not used and are
left NOT connected. They may be used
in future modifications.
This completes the HARDWARE
modifications to the RAMDISK CARD.
Next the DSR SOFTWARE must be modified
so that this ADDITIONAL MEMORY can be
accessed.
Software Modifications updated to
Ver_04 by Kevin Kapus
The original DSR CODE, CALL
SUBPROGRAMS, ETC. are located in RACKS
90-92 at the top of the RAMDISK MEMORY
MAP. The MODIFIED RAMDISK MEMORY MAP
now extends to RACK 124 and the DSR
must be moved to the new top, in RACKS
122-124.
NOTE: IF THE CODE IS NOT MOVED IT WILL
BE ERASED WHEN THE RAMDISK IS
INITIALIZED TO MORE THAN 720 SECTORS.
The changes to the CODE consist of
changing ALL REFERENCES for the three
upper 2K blocks of memory to a NEW
LOCATION, changing the LOADER PROGRAMS
to LOAD the NEW CODE at the NEW
LOCATION, changing the MAX SECTOR CALL,
and MAX SECTOR CALL, and modifying the
FORMAT ROUTINE of the DSR.
Luckily, this is much EASIER than it
might appear since the SOURCE CODE for
the HORIZON RAMDISK was provided with
the KIT and is very well Documented!
The following PROGRAMS will need to be
modified and then REASSEMBLED with the
EDITOR-ASSEMBLER. CALL/S, CREATE/S,
LOADER/S, PARTA, SVXB/S, and XB/S.
1. CALL/S
Change "CI R2,1441" to "CI R2,977"
at LABEL MAX02.
2. LOADER/S
Change "DATA >BB00" to "DATA >FB00"
at LABEL LINK.
Change "BYTE >BB" to "BYTE >FB" at
LABEL MXL1.
Change "BYTE >BD" to "BYTE >FD" at
LABEL MXL2.
Change "BYTE >BF" to "BYTE >FF" at
LABEL MXL3.
3. PARTA
Change "DATA 720" to "DATA 976" at
LABEL MAXSEC.
Change "DATA 720" to "DATA 976" at
LABEL FORSEC.
Change "DATA >BB00" to "DATA FB00"
at LABEL LINK1.
Change "DATA >BD00" to "DATA FD00"
at LABEL LINK2.
Change "DATA >BF00" to "DATA FF00"
at Label LINK3.
Add the LINES "C R8,@MAXSEC" and
"JEQ FFDONE" after the LINE "INC R8"
(fourth LINE after LABEL FMTLP1.)
Add the LINE "FFDONE MOV R8,R3"
after the LINE "JNE FMTLPO" (sixth LINE
after LABEL FMTLP1.)
4. SVXB/S
CHANGE "LI R1,>BF00" TO "LI
R1>FF00" (FOURTH LINE after LABEL
SVXB.)
5. XB/S
CHANGE "CI R2,1441" to "CI R2,977"
at LABEL MAX02.
Reassemble CALL/S, LOADER/S, SVXB/S and
XB/S to create NEW OBJECT FILES.
ASSEMBLE the ORIGINAL FILES "CHAR/S"
and "DOWNLD/S" from the HORIZON SOURCE
DISK.
Type in the following program with the
Editor Assembler.
COPY "DSK1.PARTA"
COPY "DSK1.PARTB"
COPY "DSK1.PARTC"
COPY "DSK1.PARTD"
COPY "DSK1.PARTE"
Assemble this file, use DSR256 as the
object file, with the R option.
Next RUN the "LOADER" program assembled
from "LOADER/S" to LOAD the following:
"DSR256" into BLOCK 1.
"CALL" from the assembled FILE
"CALL/S into BLOCK2.
"CHAR" from the assembled FILE
"CHAR/S" into BLOCK 3.
"DOWNLD" from the assembled FILE
"DOWNLD/S" into BLOCK 3.
Now RUN this BASIC program.
100 CALL INIT
110 CALL LOAD("DSK1.XB")
120 CALL LOAD("DSK1.SVXB")
130 CALL LINK("SVXB")
140 END
NOTE: The RAMDISK MUST be set CRU
1000 for the SVXB program to work as it
does NOT search for the HORIZON CARD
CRU like the other programs do., If you
have another CARD at CRU 1000 (like the
MYARC 128K or 512 K CARD) you can
change the sixth LINE of the "SVXB/S"
FILE from the "LI R12,1000" to "LI
R12,(CRU of your HORIZON CARD)".
The modified DSR CODE, CALL SUBPROGRAMS
ETC. are now LOADED in their NEW
locations in RACKS 122 THRU 124.
This completes the DSR modifications.
All functions of the HORIZON RAMDISK
will function as they did originally
but now being able to UTILIZE 976
SECTORS (256K).
Editors Note: The VER_04 MEMTEST I have
will not work. Use Disk Manger II's
comprehensive test to check your
upgraded ramdisk.
When formatting the 976 SECTOR RAMDISK
will show "974 SECTORS FREE" and "466
SECTORS USED". This is because the
DISKMANAGER is trying to format 1440
SECTORS and reads 466 USED during
SECTOR VERIFICATION. This does not
affect RAMDISK OPERATION in any way,
but it can be corrected to show "974
SECTORS FREE" and "2 SECTORS USED" by
changing BYTES 10 and 11 of SECTOR 0
from >05A0 to >03D0. The following
program is used to correct the SECTORS
FORMATTED number.
DEF START
SECTOR DATA >03D0
START LI R12,>1000 (CRU OF YOUR
CARD)
LI R1,7
SWPB R1
LDCR R1,8
MOV @SECTOR,@>580A
SBZ 0
RT
END START
This completes the HORIZON RAMDISK 256K
EXPANSION PROJECT for VER_04.
If you have questions concerning this
expansion project you can send them to
Kevin Kapus, 1026 Norwood Ave.,
Colorado Springs CO 80906, or phone
(303) 576-3199 or contact Edward
A. Hallett, 5600 S. Countryclub #64,
Tucson AZ 85706. Phone (602) 889-6930.
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