setting up a "combo card" on a 3b1
Karl Swartz
kls at ditka.UUCP
Sat Mar 4 19:24:18 AEST 1989
In article <1740 at umbc3.UMBC.EDU> motteler at umbc3.UMBC.EDU (Howard E. Motteler) writes:
>I just got the "combo card" from DDS (now Discovery Electronics), with
>2 serial ports and 0K of RAM, but it seems to come with zero
>documentation.
I just got one too. Fortunately, I have two UNIX PCs, one of which
already had a Combo Board that came with documentation. (We don't
need no stinkin' documentation! :-) )
To populate the memory array, you'll need your basic 41256-15 chips.
Yep, 150 ns is fine. (I think the expansion memory runs with a wait
state above and beyond motherboard memory.)
If you only want to put 0.5 MB on your Combo Board, put the chips in
rows 5 and 6. For 1.0 MB, populate rows 7 thru 10. Note that if you
upgrade from 0.5 MB to 1.0 MB, you *must* move the chips from rows
5 and 6. For the full 1.5 MB, populate everything in sight.
Now those jumpers you noticed ... they select how much memory is to
be recognized:
-- Jumper --
Memory W1 W2 W3 Rows
------ -- -- -- ----
0.0 MB off off off none
0.5 MB off on on 5 and 6
1.0 MB on off on 7 thru 10
1.5 MB on on off 5 thru 10
==> Make sure you're well grounded while playing with the board!
Static can easily leave you with a board full of monolithic
Rice Krispies. :-(
Now install the board in your machine, insert the Diagnostic Floppy
(first from the Foundation Set) and power up. After the disk boots,
the first screen should show the proper configuration, including the
Combo Board and its memory.
>From the main memu of the diagnostics, order up the subsystem test
menu and select item 5, Memory and Parity tests. Go take a shower,
walk the dog, get some coffee, whatever, while the tests churn thru
your memory.
If you're lucky, the tests won't turn up any errors. (You may want
to run them several times to flush out any weak chips.) If errors
do turn up, the next few dozen lines will help you find the dying
chip ...
A friend at AT&T (who prefers anonymity) sent the following map of
the memory layout on the board:
Even Odd Even Odd Even Odd
byte byte byte byte byte byte
Row 5 6 7 8 9 10
_________________________________________________________
| |-|
Bit-0 | #### #### #### #### #### #### | |
Bit-1 | #### #### #### #### #### #### | |
Bit-2 | #### #### #### 3 #### #### | |
Bit-3 | #### #### #### 1 #### #### |-|
Bit-4 | 2 #### #### #### #### #### |
Bit-5 | #### #### #### #### #### #### |-|
Bit-6 | #### #### #### #### #### #### | |
Bit-7 | #### #### #### #### #### #### | |
Bit-P | #### #### #### #### #### #### | |
|_______________________________________________________|-|
The 0.5 MB bank in rows 5 and 6 maps to addresses 0x300000 thru 0x37FFFF
while the 1.0 MB bank in rows 7 thru 10 map to 0x200000 thru 0x2FFFFF
and is interleaved, i.e. the word at 0x200000 is stored in rows 9 and
10 while the next word, at 0x200002, is in rows 7 and 8.
Note that the diagnostics seem to display addresses relative to the
base of expansion memory, so an error in the 0.5 MB bank will show up
as address 0x1xxxxx instead of 0x3xxxxx. The diagnostics tell you if
they're testing motherboard or expansion memory, so there should be
little room for confusion.
To isolate the proper row given the reported address:
Reported Physical Bad Bit Bad
Address Address In Word Row
-------- -------- ------- ---
0xxxxe 2xxxxe 00xx 9 e = [048C]
0xxxxe 2xxxxe xx00 10 e = [048C]
0xxxxo 2xxxxo 00xx 7 o = [26AE]
0xxxxo 2xxxxo xx00 8 o = [26AE]
1xxxxx 3xxxxx 00xx 5
1xxxxx 3xxxxx xx00 6
Within the row, find the chip based on the bad bit on readback:
Even Odd Bit/Chip
---- --- --------
0001 0100 0
0002 0200 1
0004 0400 2
0008 0800 3
0010 1000 4
0020 2000 5
0040 4000 6
0080 8000 7
For example, I had three bad chips, marked on the diagram above. The
addresses that showed up as bad were as follows:
Chip Wrote Read Reported Address(es)
---- ----- ---- --------------------
1 0001 0801 3D432, 3D436, 3DC32, 3E432, etc.
2 0001 0011 15755C
3 0001 0401 30512, B0512, 305D2, 307D2, etc.
Now that you've got all that taken care of, you're ready to boot up
UNIX. You don't need to do anything special to use the extra memory,
though you'll need to install the EIA/ROM Combo Board Expansion Disk
to make use of the new ports. I got one marked 3.0 with my first
Combo Board (the one that came with docs) and a newer 3.51 version
with the UNIX 3.51 set. Either one is apparently ok with 3.51 (I
ran with the 3.0 version for a while before I realized I had the old
version).
If you don't have either disk, I'd suggest calling the folks who
sold you your Combo Board, since an unpopulated one is pretty much
useless without that disk.
One final note: if you're looking forward to adding lots of memory
by adding several fully populated Combo Boards, you're out of luck.
Only 2 MB may be placed in the expansion memory space, regardless
of how much your motherboard has, and the only board that sticks
memory in the 0x380000 thru 0x3FFFFF range is the 2 MB board. If
you really want the extra memory, you can also do a bit of hardware
hacking on a 0.5 MB board to readdress it; instructions on that bit
of work have been posted on several occasions.
--
Karl Swartz |UUCP {ames!hc!rt1,decuac!netsys}!ditka!kls
1-505/667-7777 (work) |ARPA rt1!ditka!kls at hc.dspo.gov
1-505/672-3113 (home) |BIX kswartz
"I never let my schooling get in the way of my education." (Twain)
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