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The IC2 format

 
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Mystic_Merlin



Joined: 15 Oct 2007
Posts: 395
Location: Bangkok

PostPosted: Fri Jul 26, 2019 1:08 pm    Post subject: The IC2 format Reply with quote

Referred to as SUD (Supercom UpgraDe?), Procomms2 or SMC_IC2, The IC2 format is one that I've been looking information on since it was succinctly mentioned in some old BBS archives.
If you consider Super Magicom / Supercom being generation 1 for copiers, Pro Fighter being generation 2 for supporting Hirom games natively, then IC2 should be somewhat generation 1.5


Why?
Well, 10 years ago I came across a mod I had never seen on a Supercom to load Hirom games.
Check the whole thread here:
http://www.tototek.com/phpBB2/viewtopic.php?t=2331

I won't go into details into the SNES memory mapping schemes as you can find all this info online but basically the main difference between Lorom and Hirom is the way the 32k/64k banks are organized.

When Aragorn figured that out, he released the Mod mentioned in the above thread to upgrade SMCs. What Nintendo referred to as MODE 20 and MODE 21 in its official doc was named "low-rom"/Lorom and "high-rom"/Hirom by Aragorn.
This Mod consists into a hardware modification combined with a modified SMC bios loader, the Hirom loader.
The loader identifies the type of rom in a Pro Fighter rom header and rearrange the data in the SMC accordingly.

The mod was then simplified in a single PEEL/GAL IC soldered on the SMC bottom adapter.

What triggered my curiosity regarding that Mod and the IC2 format was that some later copiers included the Mod while not supporting the Hirom loader.
https://lh3.googleusercontent.com/OuSJRMPGatU8COLDzJNg6fxkM9d3HpgeS7snN8rpvL-FKDCUeauIulBDGo_fxhUchryIh6M6ZD3ujhVkzMM=w890-h667-rw-no
https://lh3.googleusercontent.com/Z_qV2wvhKWIHJbQwS5DX-SFXUuiG3P1amQlATwOcUDOjFE55LzAlVgh49OKrFu4m7jMn6sBVFnHuwxIQ06c=w1186-h667-rw-no

So I started to wonder: how are you suppose to load Hirom games on these machines?


How I finally figured it out

As I was using an old DOS uCON revision I found an undocumented function to convert FIG into a format called SMC_IC2, I had a look at the file generated and then I got it:
The IC2 format achieves what Aragorn's loader was doing by padding and rearranging the data chunks without the need of a pre loaded software.
Some kind of reverse logic if that makes any sense.

It's a bit of a bastard format when you look at it, I'm not surprised it was dropped quite quickly, yet it seems it has been used in quite a few copiers.
Indeed it uses quite a lot of space, the small 4MB Super Bomberman Hirom is patched to almost 10MB. The format is limited to 16M.


How come we've never heard of that format before?

Well, it was a short live format, I would think 6 month to a year, as the Pro Fighter was released pretty soon after the first Hirom games were available: Ranma 1/2 Part2, Psycho Dream, F1 Grand Prix 2...
But since many users had already purchased a Super Magicom or a Supercom, this solution was adopted by quite a few of them.
Information on the format is very scarce, even going back to the Red#9 days (NorQue Wink ) I couldn't find any on these forums.


Format specs

This is what needs to be done to convert a rom to IC2:
1. Interleave the ROM
2. Split it in 2 parts
3. 1st part needs to be padded to 8MB
4. 2nd part is the remainder
5. 1st part needs a SMC header with &80 at offset &00 and &40 at offset &02
6. 2nd part needs a header corresponding to the size of the rom left to be loaded at offset &00 and &00 at offset &02


Which copiers support that format?

At least the 6 copiers I attached on that picture. The Twin Supercom and the Future Supercom from Micro Genius are not very popular, they're both clones of the SMC with self powered FDD.
The UFO on the other hand was widely available and unless you had an upgraded 3.0 BIOS you would only load Hirom games in IC2 format.


Does uCON64 supports IC2?

Yes! Thanks to the efforts dbjh put into the development of that great piece of software Wink , you can convert using --ic2 since version 2.2.0
It shall be noted that many Hirom games are FastRom and shall need a SlowRom fix via the command --l, otherwise just pick a trained rom that has the SlowRom fix.
Last but not least the latest SVN release of ucon64 also supports parallel transfer via --xic2
VGS does also support parallel transfer of IC2


Again a big big thank you to dbjh for his continuous efforts in the development of uCON64. Thanks also to Tomy for supporting our work Wink

Now the question remains, realistically, how many of you will ever use IC2? Razz



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NorQue



Joined: 08 Jul 2006
Posts: 32

PostPosted: Fri Jul 26, 2019 2:26 pm    Post subject: Reply with quote

Haha, good work, that is quite a bit of copier archeology that you and dbjh have done there. Too bad not a lot of us will ever have the means to try it.
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conceitedjerk



Joined: 04 Jan 2004
Posts: 69
Location: Cardboard box behind Sears

PostPosted: Wed Sep 11, 2019 4:51 pm    Post subject: Reply with quote

Interesting. I may have to dig my UFO 6 out to try this.
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Mystic_Merlin



Joined: 15 Oct 2007
Posts: 395
Location: Bangkok

PostPosted: Thu Sep 12, 2019 11:35 am    Post subject: Reply with quote

conceitedjerk wrote:
Interesting. I may have to dig my UFO 6 out to try this.


Cool, let me know how it goes. The original UFO Pro 6 bios is not even able to dump hirom games and read the wrong cart size.
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DoctorBackup



Joined: 14 Aug 2005
Posts: 265

PostPosted: Sat Sep 14, 2019 4:23 am    Post subject: Reply with quote

Always nice to learn. I had forgotten
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