The VCD port is too limited in terms of access to the HW like MD unlike PCE which has an Ext. port as it should be. You need the main Saturn slot. As far as I know regarding VF3 there are rumors of two builds. One is a slot-accelerated GPU design by Core Design and one stock Saturn AM2 design which uses very low texture BGs. Of course Yu doesn't know about that. maybe b/c he was pissed that he was backstabbed with VF3 DC when getting VF3 SAT ready to ship?
The main problem with Saturn is communication between those chips and the amount of those stoopid chips. The bus-system is very limited. PS1 smokes Saturn like double in bandwith. So putting a second VDP1 in there would have meant some serious architecture reconstructuring and still you would not get double the output you hope for.
According to several ex-SOA staff members, there were two very early tech demos for Saturn VF3 doing the rounds internally. One was described as being a female character (either Pai or Aoi, depending on who you ask) practicing moves over a plain background, while the other is almost certainly the same model of Akira that was included as a sample with the Sega Graphics Library. There were also claims of the former appearing on terrestrial TV in the UK, but after years of trying to find this, I've given up searching - at the very least, we know material relating to VF3 was included in the 15-minute infomercial that Sega broadcast on Channel 4, which was little more than the same FMV sequence later featured on the Dreamcast version of VF3tb.
Speaking of that conversion, Yu Suzuki supposedly gave his blessing to Genki producing this because of AM2 lacking the resources as a result of working on Saturn VF3 while carrying what later became Shenmue over to the Dreamcast. For those who don't know, Genki was a partial breakaway group from AM2, and Yu clearly trusted them enough to begin preliminary development on OutRun 2. My understanding is that it was management within SOJ that made the call not to release Saturn VF3, fearing that a less-than-arcade-perfect treatment would harm sales of Genki's own effort. Also, there were actually two so-called revisions of Saturn VF3, both running on stock hardware, as did the prototype of Shenmue that has since been revealed in video form.
Of the two Saturn VF3 revisions known to exist, the first complete build was dated 8 July 1998 and looked quite similar to Fighters Megamix. Although it's considered a later version, the second revision had actually been shelved months before as offering better visuals at the cost of its frame rate, which was half of that seen in other AM2 games for the period such as Digital Dance Mix and the aforementioned Fighters Megamix, though it did introduce basic 3D stage geometry that was reportedly achieved by using a combination of the rarely used SCU DSP and SH1, the latter typically assigned to controlling the Saturn's disc drive. I'm not quite sure how that would have worked, but there was indeed some vague official documentation about the DSP being able to at least theoretically handle matrix transformations.
From what I was told years ago, Sega initially approved the second revision of Saturn VF3 and even sent the master for this to a Japanese pressing plant ahead of a possible release on 5 September '98, which is also the same day that Deep Fear became the console's last PAL game. Along the way, it's been conflated that AM2 was therefore planning for Saturn VF3 to launch in Europe, though I've never seen confirmation of this beyond a vague, brief listing on Sega's official website. However, that doesn't necessarily mean anything, since Sonic The Fighters was also a regular title there as well, even receiving a provisional street date of 5 May '98 before disappearing altogether.
Saying that, what are the odds that Sega Europe wasn't at least considering the possibility of giving the Saturn a more deserving send-off with both Deep Fear
and VF3? Going into production concurrent with its producer giving a speech at a press conference in November '96 where he also revealed Fighters Megamix, nothing further was shown of Saturn VF3, and my guess is that AM2 had been hoping to surprise everyone by revealing the end product close to when they were close to shipping this. A document leaked to the main writer of the SegaBase website indicated that Saturn VF3 was finally cancelled on 17 September '98, just days after its master was ordered back from the pressing plant. I've no idea whether it went into mass production, but the lack of any circulating copies points to it being recalled before that stage.
The only other concrete details I was ever able to determine involved members of the press being allowed to play the last known build of Saturn VF3 backstage at the Autumn Tokyo Game Show in October '98, where Sega's emphasis was naturally on the Dreamcast, then just weeks away from its Japanese launch. Several members of the UK official Sega Saturn Magazine (which had just released its final issue) were definitely present, as former editor Richard Leadbetter reported for "sister" site Game Online on the near-final VF3tb, also showcased at the second New Challenge conference around the same time. Despite this, he'd later deny ever being shown Saturn VF3, and it's believed that Yu Suzuki's continued silence on the matter is because he considers its failure to reach shelves one of his first great failures while at Sega, later followed by Shenmue not meeting its sales expectations.
Before long, the once untouchable Yu Suzuki was reduced to very little, and it was quite depressing to watch him go from being on such a winning streak from the mid-1980s all the way through to 2001, only to then limp away from the company he'd done so much for. I recently saw claims that VF4 almost single-handedly kept Sega financially stable, but the subsequent takeover by Sammy left the AM departments in a state where they were not allowed to take any great risks. As a result of this new conservative mindset, Yu Suzuki put his name on nothing of worth except perhaps the mostly forgotten Sega Race TV, with the ill-fated Shenmue III and Shenmue Online being something of a final straw for him as Sega's in-house equivalent to Shigeru Miyamoto.
To make a quick side note, I really must apologise to anyone unfamiliar with my sometimes exhaustive passion for Saturn VF3. I've literally spent the last two decades chasing down every last piece of information I can get my hands on regarding this unreleased conversion, though I'm frustratingly no closer to owning any code except for a few rudimentary SGL Akira samples. For those of you who know me from over at the ASSEMblergames forum, I can only apologise for repeating a lot of what I've already posted there at considerable length. For some reason, it seems as if Sega and Yu Suzuki want to continue acting like VF3 never existed. Was it really that necessary for VF4 to be so regressive as a sequel, and now Model 3 emulation is advanced enough, can't we just get the arcade original on modern hardware instead of VF2 or VF5 yet again?
Finally, it should be noted that while there
is evidence suggesting Core Design was involved with those SCUD Race materials found on some early Katana development kits, if not very early experiments relating to Tomb Raider II as well, I don't believe it's ever been confirmed that the same developer was responsible for any known version of Saturn VF3, though it's possible they did get something up and running purely for demonstration purposes using the Eclipse accelerator. On the other hand, I'm yet to see any proof this hardware was at a working prototype stage. Then again, the whole Eclipse project was allegedly being conducted without the knowledge of anyone outside SOA's walls, so would AM2 have been aware of a close third party like Core using VF3 assets? There's still so much to be determined, and I can only hope the end of now-expired NDAs might lead to new insights coming our way soon... Even some footage would be welcome!
P.S. Eclipse was definitely being created with the intention of using the Video CD Card slot, just as the upcoming Satiator device will.