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Osborne 1 - Lifeless Character Patterns

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Re: Osborne 1 - Lifeless Character Patterns

by BitFracture » Mon Jun 15, 2015 7:16 am

I've found some time to put into the Osborne again!

I've been trying to identify which chips are used by the Osborne on start-up. That way I can just target those chips and not worry about the others until later on if the need arises. The technical manual does a terrible job of explaining any sort of allocation and much less which chips that would translate to. Can anyone explain how the Osborne selects which chip to access? These chips don't have any kind of chip-select pin, and I'm not sure how they distinguish their addresses without one.
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Re: Osborne 1 - Lifeless Character Patterns

by BitFracture » Tue Jun 30, 2015 5:24 pm

Question for you all:
I have been dumping ROMs with my Arduino from many systems, but when I try to dump the Osborne ROM I get nothing, all null. The AM2732 series has a very standard pin layout, I can't imagine I've got it wrong. The exact chip is AM2732-1DC, and I am using the diagram that many new datasheets for 2732 show. None are unique. I was able to successfully dump the character ROM, MM2716Q-1 (although there were several points of corruption, compared to the ROM here http://www.retroarchive.org/maslin/roms/)

Do you think a failed ROM could result in the problems I've been seeing in my initial post?

Thanks
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Re: Osborne 1 - Lifeless Character Patterns

by Audronic » Wed Jul 01, 2015 11:29 am

@ BitFracture

I also had a problem trying to read a 2716 (very old char Gen) i tried 3 Eprom Programmers , got variable results.
Andrew Quinn suggested that i put it in a Spare ROM slot in a System 80 and then do a dump of the memory area.
This worked and i was able to confirm it by burning a replacement (Which was readable by the Eprom Programmer) ??

So if you are stuck ! maybe find some one with a System-80 over there.

Good luck

Ray ( DownUnder )
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Re: Osborne 1 - Lifeless Character Patterns

by BitFracture » Wed Jul 01, 2015 12:07 pm

That's good to know, and at least would explain why the 2716 had some small read errors. However I really need to know if anyone has had trouble with the 2732, as that is the main ROM and the one that appears blank when I try to read it.
Note that I am not using an EPROM programmer, but instead an arduino and some 74HC595N shift registers for the parallel address bits (which I've done successfully many times now).

Thanks
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Re: Osborne 1 - Lifeless Character Patterns

by tezza » Wed Jul 01, 2015 12:23 pm

BitFracture wrote:
Do you think a failed ROM could result in the problems I've been seeing in my initial post?


Without knowing the specifics of the Osborne ROM, a failed ROM in 8 bit machines generally can often lead to screen garbage and a failed boot.
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