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Using ISO images in DOS

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First post, by megatron-uk

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I'm a lazy person at heart, so I wanted to be able to play as many of my original DOS games as possible, without having to continually swap CD's around.

So at the back end of last year when I was messing around with Freedos on my P4 Dos/Win system I encountered the CDROM driver/MSCDEX replacements: SHSUCDX and SHSUCDHD.

SHSUCDX is a fairly straight forward replacement for MSCDEX, but SHSUCDHD is much more interesting... it takes a ISO image and creates a device for it in the same manner as a normal cdrom driver loaded via config.sys would do.

The *really* interesting thing about both bits of software is that they can be dynamically loaded and unloaded from memory at will. In addition, they also work fine in MS-DOS, so you don't have to be running a Freedos system to use them.

So what I've started doing, for those games that always check for a CD in the drive in order to run (either for 'copy protection' or simply to run movies or data files from), is create a small batch file that loads the driver, maps it via the mscdex replacement, call the game, and then unload again.

It seems to work very well in the games that I've tried it with (so far!). Now, of course anything that relies on CD Audio is not going to be very happy, but for 99% of games I'd be using GUS or a midi device anyway.

A typical batch file would be:

SHSUCDHD /D:F:\ISO\ALBION.ISO
SHSUCDX /D:SHSU-CDH
CD F:\GAMES\RPG\ALBION
ALBION
SHSUCDX /U
SHSUCDHD /U

The drivers can user upper memory, so with both programmes loaded they use approximately 8kb of base memory. For reference my config has 602kb free without SHSUCDHD and SHSUCDX running and 594kb with (I'm not using umbpci.sys).

Just thought this could be a useful tip for anyone who hasn't come across these neat little drivers yet!

Reply 1 of 25, by Gamecollector

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No mixed-mode cd support, anything with CDA is not playing correctly.
SHSUCDX is not 100% compatible with mscdex.
Except this two - thx for the idea.

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Reply 2 of 25, by megatron-uk

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Yep, cd audio won't work as there's no practical way of routing an audio stream. I was looking at this more from the point of view of having cd-rom support for those games that refuse to run without a disc in the drive, or have no way of copying (for example) movies or game data to disk.

Reply 3 of 25, by Mystery

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Does SHSUCDHD have any minimum requirements?
I'm using it on a Pentium 233MMX and the transfer rate is just abysmal. Loading is at least 5 times slower than from a regular CD-ROM. I was expecting it to be faster, but the opposite seems to be the case. Just starting a setup program from CD takes several minutes.

Any advice? Does it have issues with smartdrv?

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Reply 4 of 25, by jwt27

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Mystery wrote:

Does SHSUCDHD have any minimum requirements?
I'm using it on a Pentium 233MMX and the transfer rate is just abysmal. Loading is at least 5 times slower than from a regular CD-ROM. I was expecting it to be faster, but the opposite seems to be the case. Just starting a setup program from CD takes several minutes.

Any advice? Does it have issues with smartdrv?

On my PII-350 it is much much faster than from CD. Have you tried using UIDE as disk cache?

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Reply 5 of 25, by Mystery

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Well UIDE didn't help with the SHSUCDHD performance, but it did solve a different problem.
I was trying to use SHSUCDHD for a game that had stuttering video from CD, so I was hoping for better performance off the HDD.

With UIDE the videos play just fine from the CD, so thanks for the advice.

Although it would still be nice to get SHSUCDHD working 😉

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Reply 6 of 25, by dosquest

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I was looking at this more from the point of view of having cd-rom support for those games that refuse to run without a disc in the drive

I was able to accomplish that, if you want look at my Harvester post.

Reply 7 of 25, by megatron-uk

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dosquest wrote:

I was looking at this more from the point of view of having cd-rom support for those games that refuse to run without a disc in the drive

I was able to accomplish that, if you want look at my Harvester post.

The posts above refer to using ISO images on real DOS systems, not in Dosbox.

Reply 10 of 25, by Harekiet

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I've got it setup to normally use the regular cd drive but i can override that with some mount blah /umount bat files which will mount blah.iso from d:\isos whatever and umount will switch back to regular cd drive. Quite a handy cdrom driver compared to mscdex

Reply 11 of 25, by Mystery

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Well it's working on my system, the performance is just incredibly slow and I was wondering if there's a certain requirement you have to meet to make the SHSUCDHD ISO faster than the real CD.

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Reply 12 of 25, by Jorpho

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Perhaps your ISO image is fragmented?

Mystery wrote:

Does it have issues with smartdrv?

I suppose you already tried disabling smartdrv to see if that made a difference?

Reply 13 of 25, by Mystery

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Yes I tried disabling smartdrv and I also tried the UIDE disk cacher.

I don't think it's fragmentation. Even the directory listing is stopping every 10-20 files when listing a longer directory.

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Reply 14 of 25, by dosquest

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@mystery well, seeing as I am lazy, I am hoping to write the guide one day and then go back in time and have you change your replies saying "Thanks! Wow! That guide helped me!"

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Reply 15 of 25, by megatron-uk

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dosquest wrote:

@mystery well, seeing as I am lazy, I am hoping to write the guide one day and then go back in time and have you change your replies saying "Thanks! Wow! That guide helped me!"

Yeah, well until that time it really doesn't help anyone else now, does it?

Reply 16 of 25, by megatron-uk

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Mystery wrote:

Yes I tried disabling smartdrv and I also tried the UIDE disk cacher.

I don't think it's fragmentation. Even the directory listing is stopping every 10-20 files when listing a longer directory.

I can't help there, sorry. I've used the same technique on a P4 3.06GHz with Freedos, a PPro 200 with Dos 7.1 and the AMD X5-133. Performance has been much faster than the actual cdrom in all situations; I generally don't have smartdrv, uide or any other IDE 'speedup' drivers loaded (I figure the cache memory on most modern hard drives is way more than we had back in the 80's and 90's, so don't tend to use cache software).

Reply 17 of 25, by keropi

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I am using fakecd and fakedr ... they work pretty good with a high success rate if you let them collect data from the original CD (ofcourse CDDA is not working like on other solutions)

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Reply 18 of 25, by Mystery

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megatron-uk:
Hm, so it's not the system's performance. The 233MMX should easily outperform the X5-133 and probably the PPro200 as well.
That's really weird. I can't even list a directory without lots of delays.
I use smartdrv or uide since I don't use modern HDDs in the system which still get a notable boost from these tools.

keropi:
Thanks for the tip, I'll give fakecd/fakedr a shot 😀

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