Hi James (and others),
However, this is where I got stuck and it's due to my poor knowledge of how things work at the bit level for 16 Bit machines. I can't figure out how to translate this to exactly which bit this is and also what column? I do know what binary is and how it (and hex) translates to things regarding 8-bit but not really at the chip level . Are you able to elaborate (or point me to a URL) on how this is translated? I assume these words are in hex? I assume so if you can get something like 4000.
Once I know what IC to replace I'll change it and see if the rule of thumb works.
Thanks
Terry
>
> The Lisa's power-on self-test attempts to provide information for
> repairing memory boards.
>
> While writing this, I was able to pinpoint a specific chip and repair a
> bad board, but I could have parts of this wrong. Hopefully others will
> report successes and failures and the technique can be more firmly
> established.
>
> During the self test, the results of the memory test are stored in some
> low memory locations (accessible from service mode).
>
> Beginning at $186, there are 16 words of bit error information; these 16
> correspond to the sixteen 128K blocks in the 2MB RAM address space. The
> Apple 512K memory boards have 4 rows of chips (each row being 128K). This
> means that 4 of the test result words will exactly correspond to the 4
> rows of a memory board.
>
> Each word contains bad bit information... a bad data bit is reported by
> the corresponding bit set to 1 in the word corresponding to the 128K
> memory block where it was found.
>
> It is easy to associate the bad data bits with the coordinates of a column
> of 4 chips on the memory board; from the schematic: bit 0 is column 22,
> bit 7 is column 15, bit 8 is column 1 and bit 15 is column 8.
>
> The rows of 128K are designated B, C, D, and E by the coordinates on the
> board. However there is a complication or two...
>
> The 16 words are according to logical address, not physical address, and
> it is, of course, a physical chip we're looking for. The complication is
> that the physical rows are mapped to logical addresses in a different
> order depending on which slot the board is in.
>
> If you have one memory board, regardless of which slot it is in, it will
> always be associated with the first 4 words... $186 - $18C.
>
> If you have two 512K memory boards, the first 4 words are associated with
> slot MEM 1, and the next 4 words are associated with slot MEM 2.
>
> The four rows of the memory board are always mapped in BCDE or EDCB order
> (depends on the slot), so you can be confident that a single bit error
> maps to one of two rows... if the error is in the first or last of four
> words, then the problem is row B or E. If the error is in the second or
> third word, then the problem is C or D.
>
> To figure out which of the two rows is the problem, you can read-up on the
> physical-logical address mapping scheme in the Lisa Hardware Reference
> Manual, and cross-reference that through the schematic to determine which
> physical row is going to correspond to which logical address block.
>
> Or you can use a rule of thumb determined by observation.
>
> I expect the latter will be more useful.
>
> I have observed that for slot MEM 1, the order is BCDE, and for slot MEM2,
> the order is EDCB.
>
> Examples:
>
> A. 1 RAM board installed, error reported in first 4 words...
> - 0000 4000 0000 0000
> - error in bit 14 which is column 7
> - if the board is in MEM 2, the second word corresponds to Row D
> - if the board is in MEM 1, the second word corresponds to Row C
>
> B. Error in second 4 words...
> - 0000 0000 0000 0000 0020 0000 0000 0000
> - this might happen if you have 1MB of RAM - 2 boards
> - error in bit 5 which is column 17
> - the second 4 words corresponds to MEM 2
> - the first word (of the second 4) corresponds to Row E
>
> Summary of the rows corresponding to the first 8 words starting at $186
>
> 1 board in slot MEM 1
> - B C D E x x x x
>
> 1 board in slot MEM 2
> - E D C B x x x x
>
> 2 boards
> - MEM 1 MEM 2
> - B C D E E D C B
>
>
> Complication #2
>
> You may have noticed something missing... there are 18 columns of chips,
> not 16. The extra 2 are for parity bits, one for each byte.
>
> If there was a parity error, then all the data bits might be clean,
> represented by 0 in all 8 words at $186. In this case, you will get error
> 71 instead of 70 from the memory test.
>
> I have not been able to observe this case, but from the ROM source listing
> it appears that in the case of a parity error:
>
> - long word $270 contains the logical address where the error occurred
> - byte $27C contains a number that corresponds to the row (eg. 2 for row D
> when the problem board is in MEM 1)
> - byte $27D contains $9 or $14, which correspond directly to the board
> coordinate column of the bad parity chip, column 9 or 14.
>
> Miscellaneous
>
> - To enter service mode, type Apple-S after the memory error is reported
>
> - To display the 16 words at $186 type: 1186 20<return>
>
> - If your memory board has a serious problem in Row B or E, then the Lisa
> might not work at all, since it needs some working memory to do the
> self-test. In this case, try moving the board to the other slot, and/or
> add a good board in the other slot. These will change the logical address
> of the bad row and may allow the Lisa to work well enough to perform the
> self-test.
>
> - This information applies to the long test. There is a short test that is
> performed after a warm reset; I believe it consolidates all the bit errors
> into the one word at $186, ie. the row(s) are not decoded. To make sure
> you are getting the long test, first turn off the Lisa, and if you have
> batteries on your I/O board, turn off the switch (and check the FAQ about
> removing the batteries to prevent corrosion damage).
>
> - This information is specific to the 512K Apple memory boards. If you
> have a different memory board you'll still get the error results, but
> mapping them to a physical chip is not addressed here.
>
> Caution!
>
> As some of this was determined by observation, and some by interpretation
> of the ROM listing, it would be good to have some independent confirmation
> before I add this to the LisaFAQ... please report your own experience!
>
>>>Has anyone on the list had experience of the Lisa Test program? I
>>>have a couple of faulty memory cards on my third Lisa and wonder if
>>>this program will let me identify the exact chip(s) that might have
>>>failed?
>
> It would be good to know if Lisa Test makes troubleshooting easier than
> this procedure... comments or experience?
>
> James
>
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-- ----- You received this message because you are a member of the LisaList group. The group FAQ is at http://lowendmac.com/lists/lisa.html To post to this group, send email to lisalist_at_email.domain.hidden To leave this group, send email to lisalist+unsubscribe_at_email.domain.hidden For more options, visit this group at http://groups.google.com/group/lisalistReceived on 2015-07-15 16:53:20
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