Running it through a riser card shouldn't hurt performance, as they are usually just a straight through connection to the motherboard.

Not enough for you to notice, would prefer there be a short path to the rest of the system but even with those rise cards there won't be much difference to notice. I usually don't like such systems because they are limiting on how much that I can cram in.

I am a little limited for expansion compared to my SS7 build. But Despite the lack of AGP (it is an older system after all) there is room for a VooDoo 1 card, the onboard S3 Virge should suffice for 2D, there are 2 USB ports on the back of the board so it should be ok. I know there is a deep love of soundcards on Vogons by many of the posters, but I'm quite happy to just throw in an AWE32 or even an SB16/128 and have sound. After all, when your throwing slugs at imps and barons of hell while circle straffing a cacodeamon, do you really have time to appreciate the sound? 😘

I've always wondered why OEM's used riser boards instead of just putting the slots directly on the motherboard. Putting them on a separate board has to cost more than just using a standard AT/ATX layout. There's also the expense of having to get custom cases made instead of using already available standard cases and the same for all that unique voltage crap requiring non-standard PSU's that they used to engage in years ago. Even if they had to pay royalties to use standard parts, it can't cost anything close to what it would cost to engineer their own proprietary parts, not to mention all the ill will they spread among their customers who later try to upgrade their systems and find that their OEM has handcuffed them into buying a new computer instead of upgrading.

It seems you answered your own question 😁

Main advantage to the riser is that you can have full-height expansion cards in a low profile desktop case, by having them parallel to the motherboard instead of perpendicular.

I'd guess that the riser board PCs are bought in vast numbers by businesses and goverment, and the vast majority will never get upgraded. They probably come with options for one or two upgrades at the time of purchase. They'll get used for 2-5 years, after which it will pretty much always be more cost effective to replace them completely than upgrade. Compared to a fully-fledged upgradeable PC they will be cheap to buy, compact to deploy in increasingly limited office space, and simple to support and maintain.

In my limited experience the PSUs are sometimes are so weedy - doubtless to limit heat in a restricted space as well as keep costs down - that filling the riser with cards can blow them.

Back to the OP, I've got an socket 7 AST box I've been wondering about adding a v1 to as well - it also has an aztech sound card and a modem iirc. But at the end of the day, I think I'm going to chuck it instead. It'll be so limited it's just going to annoy me.