i've done a bit of testing with doom on a p90 with the RZ1000 controller and a 1996 IDE drive, so a fairly period correct setup. i think it confirms what i said earlier - there really doesn't seem to be much of a benefit for smartdrive with doom engine games. whether it's loaded or not, upon first encountering an asset, the blue floppy icon will flash up and there can be a bit of stutter, particularily with sounds. though with that setup it's really not too bad.

according to info regarding the limit-raising .exe hacks, vanilla doom has an 8 mb heapsize. the startup screen mentions 0x800000 being allocated for zone memory, which is perhaps it. that should be more than enough for all the assets in the game, making smartdrive redundant. however, i was at least expecting a benefit with exiting and restarting the game - in that case, obviously assets have to be cached in at first again. this is still the case with smartdrive, so i'm not sure it's working properly at all with this game. running smartdrv 8192 /x with 32 mb of ram here. the only possible benefit i saw is that it may take off half a second or a second of initial loading time, though didn't bother timing it, and the loading for this game is fast enough anyway.

edit: after some more testing i did find where exactly smartdrive is beneficial here. it looks like that upon dying in the game, for some reason assets are cleared out from memory and everything has to be loaded again upon first encounter, with the blue floppy icon flashing. with smartdrive that is not the case, this can easily be checked by dying and pressing a key to reload the map - without smartdrive the blue floppy icon will come up, with smartdrive it won't.

Quick update. Found out about four more HDD cache utilities, PC-Kwik, Flash, Vcache and Vastcache. All were available by 1989, at least.

egbertjan wrote on 2024-10-16, 20:56:

I read all kinds of things here that should go slower if I turn off smartdrive. I can't imagine that with an SSD samsung 850 pro in dos 6.22 with IDE driver from ali chip that puts it in udma 2 on 33mb it becomes slower without smartdrive. By loading the ali hdd driver the access time of the ssd and therefore speed has improved a lot and loading games and programs in dos has become much faster. Is it still necessary to use smartdrive in this situation?

Yes, it is still necessary. Because of the way DOS programs work. And, the memory speed is faster than SSDs anyway.

One of the games that made me a believer is Godfather III. It's a so-so game, but the difference between using smartdrv and not is quite substantial. The game loads very fast even the first time starting it, when smartdrv is loaded.

There's no reason to not load smartdrv in 286 and above, since it can be loaded into upper memory. (Yes, certain 286s too - with RDOSUMB).

It's safe to use even with defrag, and actually defrag runs faster with smartdrv.

a few KB links about smartdrive settings, cache size etc. that are good to keep in mind:

http://www.manmrk.net/tutorials/DOS/help/smartdrv.htm
https://jeffpar.github.io/kbarchive/kb/094/Q94604/
https://jeffpar.github.io/kbarchive/kb/095/Q95531/

also, for doom engine games, the IWAD files are typically around up to 20 megabytes in size. i had the idea to try a rather huge smartdrive cache of 24 megabytes, which in layman logic should cache the entire IWAD and a savegame, but it doesn't work like that - reloading the save still triggers loading off the HDD. does anybody know why that is? as microsoft said, it looks like sizes over 2 mb show less of a benefit.

with that in mind, a ramdrive really would be the only way to force all of those games to make use of extra RAM. the main problem that i see with it is, even when writing a batch file that automates the save copy after exiting the game, a game crash would result in lost progress, because any save up to that point wouldn't have been copied over. so i'm wondering if there is any kind of 3rd party DOS ramdrive that can automatically copy over the file while the game is still running.