[Coladam] ROM question for ADAM
oltmansg at bellsouth.net
Tue Aug 26 07:24:31 CEST 2008
I'll take a stab at this, but anyone else feel free to jump in...
I believe that U20 is the first that is accessed. According to the
schematic, U8, U20-22 are all 2764s. On just about every system I've
ever seen U8 is not populated, however I have one right now that has
all four loaded with EPROMS instead of the normal mask programmed
ones. On the EPROM board, U22 is a 27128 (16k), and the rest are 2764s
(8k). The EEPROMs at U8 and U20 are labeled ALF2 and ALF1 respectively
(anyone know what ALF stands for?), U21 and U22 are labeled EOS. U8
and U20 have enough addressing lines hooked up for 16k.
According to the ADAM Technical Manual, the MIOC selects the
SmartWriter ROM first and runs the EOS_BOOT routine in that code
first, attempts to find an Expansion ROM (this goes in the middle
slot). If it can't find expansion ROM, then it will try the drives and
attempt to find a boot sector. If it does, it will copy that to C800
and run that code, else it will start the SmartWriter up.
Based on this info and the schematic (and the fact that the Z80
processor starts executing at address 0), I believe that U20 is the
first one to run.
It looks to me that U21 and U22 can accommodate up to 27256s (15
address lines are hooked up). I think this depends on how the board is
configured though, as there are notes on the schematic where the
address decoding circuitry can be removed and a couple jumpers added.
On a related note, can someone explain what the gadget does that sits
underneath the a couple of the ROMs?
On Aug 25, 2008, at 2:58 PM, Joe Blenkle wrote:
> I got a question via my web page and can't answer it...can anyone
> give me the answer to this:
> Do you know which size (16K,8K) ROMs are at U20,21,22? Which one is
> EOS, and which is the first accessed?
> Joe Blenkle
> Coladam mailing list
> Coladam at adamcon.org
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