][+ ROM Testing [message #383266] |
Sat, 20 April 2019 17:27 |
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Originally posted by: frank_o_rama
Hello All,
I'm attempting to repair a ][" from the monitor.
C050 C053 C054 C057 N 265:FF N 266<265.BFFEM 266<265.BFFEV 265:0 N 266<265.BFFEM 266<265.BFFEV 34:14 (Return)(space before the return)
If I hook up a working drive it will load the first few sectors, then crash to the monitor with a few random characters showing on screen. I'm wondering if there is a way to test the ROM contents from the monitor since I'm unable to boot the ][+ Dealer Diagnostics. The drive and card work on another machine. Thoughts?
f
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Re: ][+ ROM Testing [message #383291 is a reply to message #383266] |
Mon, 22 April 2019 02:14 |
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Originally posted by: groink_hi
I don't think there's any method via just the monitor alone.
The only way I would know how to do this is to pull the ROMs, develop an adapter so that a programmer device would recognize the ROMs as a 2716 EPROM, and then use the programmer to read/save the ROM contents. You could then download good ROMs off the Internet, and then use a DOS command to compare the binaries.
For MS-DOS, you can use the "fc" command like this:
fc GOOD-D0.bin MY-D0.bin
And if your ROM is good, it should show "FC: no differences encountered"
Anything else, your ROM is probably bad.
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Re: ][+ ROM Testing [message #383292 is a reply to message #383266] |
Mon, 22 April 2019 02:52 |
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Originally posted by: James Davis
On Saturday, April 20, 2019 at 2:27:58 PM UTC-7, frank_...@hotmail.com wrote:
> Hello All,
>
> I'm attempting to repair a ][+ which is having problems. I found some bad RAM already and replaced it. It now passes the 48K memory test from "Understanding the Apple ][" from the monitor.
>
> C050 C053 C054 C057 N 265:FF N 266<265.BFFEM 266<265.BFFEV 265:0 N 266<265.BFFEM 266<265.BFFEV 34:14 (Return)(space before the return)
>
>
> If I hook up a working drive it will load the first few sectors, then crash to the monitor with a few random characters showing on screen. I'm wondering if there is a way to test the ROM contents from the monitor since I'm unable to boot the ][+ Dealer Diagnostics. The drive and card work on another machine. Thoughts?
>
> f
If the drive and card still work on the other machine afterward, then the problem is not damaging them. It must be the A2+ that is BAD, for sure.
Have you tried using the "SAMS Apple II Troubleshooting & Repair Guide"?
ftp://public.asimov.net/pub/apple_II/documentation/hardware/ misc/sams/Sams Apple%20II%20Troubleshooting%20&%20Repair%20Guide.pdf
It covers the Apple II Plus and the Apple IIe.
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Re: ][+ ROM Testing [message #383293 is a reply to message #383266] |
Mon, 22 April 2019 02:55 |
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Originally posted by: James Davis
On Saturday, April 20, 2019 at 2:27:58 PM UTC-7, frank_...@hotmail.com wrote:
> Hello All,
>
> I'm attempting to repair a ][+ which is having problems. I found some bad RAM already and replaced it. It now passes the 48K memory test from "Understanding the Apple ][" from the monitor.
>
> C050 C053 C054 C057 N 265:FF N 266<265.BFFEM 266<265.BFFEV 265:0 N 266<265.BFFEM 266<265.BFFEV 34:14 (Return)(space before the return)
>
>
> If I hook up a working drive it will load the first few sectors, then crash to the monitor with a few random characters showing on screen. I'm wondering if there is a way to test the ROM contents from the monitor since I'm unable to boot the ][+ Dealer Diagnostics. The drive and card work on another machine. Thoughts?
>
> f
If the drive and card still work on the other machine afterward, then the problem is not damaging them. It must be the A2+ that is BAD, for sure.
Have you tried using the "SAMS Apple II Troubleshooting & Repair Guide"?
ftp://public.asimov.net/pub/apple_II/documentation/hardware/ misc/sams/Sams%20Apple%20II%20Troubleshooting%20&%20Repa ir%20Guide.pdf
It covers the Apple II Plus and the Apple IIe.
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Re: ][+ ROM Testing [message #383310 is a reply to message #383266] |
Mon, 22 April 2019 17:22 |
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Originally posted by: frank_o_rama
Thanks guys.
I had another idea; a short ML program which does an EOR over the ROM contents and can provide a checksum. Then I can compare against whatever value my emulator comes up with to see if they're equal.
But, this weekend I swapped the ROMs with another known-good machine and the problem is still there. Swapped a ton of chips (RAM refresh, bus driver, ROM select, etc) to no avail. Thought the RAM was good, but maybe something intermittent happening. The disk I'm using to boot (Short Circuit), does a zero-page checksum at the point it's crashing.
f
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Re: ][+ ROM Testing [message #383320 is a reply to message #383266] |
Tue, 23 April 2019 10:18 |
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Originally posted by: frank_o_rama
Well, I came up with a checksum test, but unfortunately there's a collision happening with the ][, for example).
ORG $0300
prbyte EQU $FDDA ;print accumulator as 2 character byte
cout EQU $FDED ;print accumulator as character
start LDY #$00 ;clear index
LDA #$D0 ;start with D0 ROM ($D000-D7FF)
STA $FF
LDA #$00 ;(indexed)
STA $FE
chip LDA $FF
JSR prbyte ;show which chip we're doing
LDA #$AD ;"-"
JSR cout ;add spacer character
LDA #$00 ;zero out checksum for each ROM
LDX #$08 ;do groups of $0800
page EOR ($FE),Y
INY
BNE page
INC $FF
BEQ done ;we've finished $FFFF if this is zero
DEX
BNE page ;fall through to byte if we finished a chip
byte JSR prbyte ;show checksum
LDA #$8D ;carriage return
JSR cout
JMP chip ;do next chip
done JSR prbyte ;show last checksum
RTS
CALL-151
300:A0 00 A9 D0 85 FF A9 00
:85 FE A5 FF 20 DA FD A9
:AD 20 ED FD A9 00 A2 08
:51 FE C8 D0 FB E6 FF F0
:0E CA D0 F4 20 DA FD A9
:8D 20 ED FD 4C 0A 03 20
:DA FD 60
300G
should come up with the following on a ][+:
D0-00 (highly suspicious as 00 could also mean no chip installed)
D8-B7
E0-E4
E8-86
F0-87
F8-96
f
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