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 Post subject: ISA based dev system?
PostPosted: Wed Jan 25, 2006 12:09 pm 
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Sorry, I"m still a newb, so these posts are going to continue for a bit. At the very least, I'm familiarizing myself with Cadaver's and SnoBro's code examples and learning more about the NES all the time.

Anyway, I stumbled across this article linked over at hackaday.com:

http://www.mycgiserver.com/~thelinuxmaniac/isa/

The example shown has 32-bit in and 32-bit out capability on an home-built ISA card. The circuitry is farily straightforward, with a few address decoders and latches to get the job done.

I figure one could run a few fat ribbons from such a custom PC card, straight to a modified cart or even down to the guts of the console itself (or copynes for that matter). The extra I/O lines could be used to emulate controllers, and possibly even the power and reset buttons.

The result would be a completely closed-loop development station w/o need of an emulator. The PC effectively *becomes* the game cartridge, leaving the good 'ol NES hardware to do the dirty work.

I guess the PC software side might be somewhat problematic. While operating out of sync with the NES' internal clock, I guess you'd have to rely on an IRQ or just poll those ports really damn fast. Also, you'd have to implement mapper emulation, but I suppose that can be harvested from most any emulator project (not to mention .nes file loading).

Any thoughts out there on this? Is this just pure fantasy, or could this actually be done?


Last edited by pragma on Wed Jan 25, 2006 12:47 pm, edited 1 time in total.

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PostPosted: Wed Jan 25, 2006 12:34 pm 
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Should be, I know there is a multi cart reader for the isa slot called the io-56.
http://www.reinerziegler.de/io56.htm


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 Post subject:
PostPosted: Wed Jan 25, 2006 12:47 pm 
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gannon wrote:
Should be, I know there is a multi cart reader for the isa slot called the io-56.
http://www.reinerziegler.de/io56.htm


Interesting. At a minimum the parts list might come in handy. :)


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 Post subject:
PostPosted: Wed Jan 25, 2006 12:48 pm 
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I like the idea but ISA slots are obsolete technology with two major upgrades since then. (PCI, PCI-E) Perhaps a PCI Card would be a better starting point.

Edit: Spelling correction.


Last edited by danimal on Wed Jan 25, 2006 1:58 pm, edited 1 time in total.

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 Post subject:
PostPosted: Wed Jan 25, 2006 1:03 pm 
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danimal wrote:
I like the idea but ISA slots are obsolete technology with two major upgrades since them. (PCI, PCI-E) Perhaps a PCI Card would be a better starting point.


Agreed. However, PCI development is a completely different ball game mostly due to the pin density at the card's edge, and its various modes of operation (see below). If anything a custom PCI card is intimidating, but not impossible:

http://elm-chan.org/works/pci/report_e.html

AFAIK, the PCI spec is also closed (as if that ever stopped anyone around here):

http://www.hackaday.com/entry/1234000473062256/#c504995
http://www.pcisig.com/membership/join_pci_sig/

For those reasons, I figured that ISA would be an easier starting point (but who wouldn't want a PCI card instead, right?). Plus anyone taking this on wouldn't have to worry as much about trashing an older system. ;)


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 Post subject:
PostPosted: Wed Jan 25, 2006 1:59 pm 
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pragma wrote:
For those reasons, I figured that ISA would be an easier starting point (but who wouldn't want a PCI card instead, right?). Plus anyone taking this on wouldn't have to worry as much about trashing an older system. ;)


Yes that is very true but I don't have ISA slots in my computer any more. I doubt most of us still do.


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 Post subject:
PostPosted: Wed Jan 25, 2006 2:39 pm 
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well, my fastest computer is still 450mhz (I really need an upgrade). I make up for that though by having 7 computers at the desk I'm sitting at and a kvm. Might not be able to multi-task on a single machine, but when one gets bogged down I can just switch.


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 Post subject:
PostPosted: Thu Jan 26, 2006 10:15 pm 
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Location: NE Indiana, USA (NTSC)
It'd probably best to run the carts in a typical "ROM emulator" setup (no connection to programs such as FCEU and Nintendulator which are more often called "simulators" in the embedded world).


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PostPosted: Fri Jan 27, 2006 7:49 am 
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tepples wrote:
It'd probably best to run the carts in a typical "ROM emulator" setup (no connection to programs such as FCEU and Nintendulator which are more often called "simulators" in the embedded world).


Gotcha. I'm no EE wizard by any stretch (I'm a software guy really), so I was unaware that there was a proper name for such a thing. Thanks!

This also gets part of the way toward a concern I had which was the switching latency involved with emulating a mapper in software. Again, my lack of education here leaves me stabbing in the dark at this one.

I guess the problem I'm looking to solve is how to decrease the development iteration time for making a good mapper for use in a custom cart. I know that the "FunkyFlashCart" and "Squeedo" are around the corner, but who knows when? In the meantime, I'd like to have something real to develop against but w/o the added turnaound time of reprogramming a fpga *and* roms.


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 Post subject: SNSRAM
PostPosted: Fri Jan 27, 2006 7:11 pm 
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pragma wrote:
In the meantime, I'd like to have something real to develop against but w/o the added turnaound time of reprogramming a fpga *and* roms.

Get yourself an SNROM board (common as dirt: Metroid, Zelda, etc), rewire it for whatever ROMs you prefer, and modify it to read a PRG and CHR segment of up to 8 KB each from the controller port. Then run a cable to your PC's parallel port and send the program that way.


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