Re: TI-H: direct bus access
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Re: TI-H: direct bus access
Does anyone know the pin number on the CPU or some other place to get the
I/O enable that you mentioned?
Chris Lambert
clambert@geneva.edu
calan@hotmail.com
URL: www.geocities.com/siliconvalley/peaks/6869
On Wed, 21 Jan 1998, Bryan Christopher Turner wrote:
>
> >
> > No. The 6800 can directly address 16MB. Over that ammount you need memory
> > addressing such as EMS, but not with the 6800. The ROM needs to be edited,
> > or an EMS clone since it only supports 256k. If the ROM were edited, the
> > processor could handle over 256k. If anyone is interested in the rom
> > hacking, I can give you my cracked rom if you don't give it to apple... ;)
> >
>
> Yes, the 68K can access 16MB without paging, however the chip in the TI-92 is
> NOT a normal 68K like the one in the Macs. It only has 20 address lines that
> we know of, the upper four bits create a mask for chip enable lines (one for
> RAM, one for internal ROM, one for external ROM, and one for IO ports). Thus
> you are limited to RAM addresses $00 0000 - $0F FFFF, and either the internal
> or external ROM addresses (whichever one is NOT present), and addresses above
> $60 001F. This still leaves plenty of memory in between, but the TI ROM would
> not be able to play with the non-consecutive stuff since it's memory movement
> algorithms aren't written for broken memory segments.
>
> I'm playing with the idea of a 1 meg expansion. I don't see much need for
> anything more on a TI-92 right now. It's not like you're going to use up 1 meg
> with the stuff out there now anyway. (and loading 1MB from an I/O line running
> at 9600 baud is gonna take awhile)
>
> --Bryan
> bcturner@eos.ncsu.edu
>
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