IDE to Compact Flash as MS-DOS boot drive.

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IDE to Compact Flash as MS-DOS boot drive.

Postby Paddan1000 » 2012-5-22 @ 21:50

I'm thinking of fitting my DOS-computer with an "SSD" consisting of an IDE to Compact Flash adapter with a CF memory card in it.
The problem is that the computer refuses to boot from hard drives larger than slightly above 500 MB, no matter the size of the boot partition. I haven't been able to determine the exact hard drive limit, but I suppose it's because of the limits of CHS-addressing, even though the computer accepts larger disks than that as secondary storage devices.
The Compact Flash cards come in sizes like 128, 256, 512 MB, etc... According to Wikipedia the hard drive size limit for CHS is 504 MB, although there seems to be some complicated exceptions that perhaps my computer complies to. Does anyone have any experience of successuflly using a 512 MB Flash Disk in a 486 or older, or do I have to use a 256 MB card instead?
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby vetz » 2012-5-22 @ 21:55

I've tried this once, but the performance was awful. Huge lag on the whole system and even worse performance than using an old IDE drive. Maybe I had a bad adapter or card or did something wrong. I used a 512mb card and it was installed in the computer in my signature. So I cant help specifically with your question, but I do remember I needed another IDE drive installed or else it refused to boot. I had the autoexec, ms-dos and drivers on this drive and when that was loaded I could access the card.

Combine the need to still have a noisy harddrive installed to boot and the bad performance the whole project for my part was a failure :(
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby DonutKing » 2012-5-22 @ 22:22

Look for Ontrack Dynamic Drive Overlay software, this should allow you to boot with larger drives. I've successfully used this to boot a 2GB CF card on a 486.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby nforce4max » 2012-5-22 @ 23:02

Just be sure to hunt down a decent adapter as some are extremely slow.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby Old Thrashbarg » 2012-5-23 @ 00:08

Just be sure to hunt down a decent adapter as some are extremely slow.


Uh, speed is determined entirely by the CF card itself, not the adapter. CF cards are already IDE devices, just with a smaller connector, and all the CF->IDE adapter does is pass the signals through between the different size connectors. It can't have any effect on speed... it either works or it doesn't.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby nforce4max » 2012-5-23 @ 15:38

Old Thrashbarg wrote:
Just be sure to hunt down a decent adapter as some are extremely slow.


Uh, speed is determined entirely by the CF card itself, not the adapter. CF cards are already IDE devices, just with a smaller connector, and all the CF->IDE adapter does is pass the signals through between the different size connectors. It can't have any effect on speed... it either works or it doesn't.


Not always but then again I look up the specs before I buy CF cards. Asian sites sometimes post very good performance reviews of CF cards.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby Paddan1000 » 2012-5-23 @ 16:43

Will the Ontrack Dynamic Drive Overlay software use precious kilobytes of conventional memory? I already have an IDE controller in the computer that could let me access larger hard drives, but I disabled its internal BIOS since it needed some RAM to work.
I think I'll try with a 256 MB Compact Flash card for the boot drive, since I don't need more space anyway. Then I'll use a 4 GB or 8 GB one for storage. Now, I'm off to the Swedish equivalent of Ebay to get what I need.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby megatron-uk » 2012-5-23 @ 20:22

Paddan1000 wrote:Will the Ontrack Dynamic Drive Overlay software use precious kilobytes of conventional memory? I already have an IDE controller in the computer that could let me access larger hard drives, but I disabled its internal BIOS since it needed some RAM to work.
I think I'll try with a 256 MB Compact Flash card for the boot drive, since I don't need more space anyway. Then I'll use a 4 GB or 8 GB one for storage. Now, I'm off to the Swedish equivalent of Ebay to get what I need.


Some drive overlay software uses the top 1kb of 640kb base memory to hold the drive information which would normally be provided by the BIOS (some BIOS implementations already do that anyway). Other than that, no, there's no driver or anything loaded in order to use it.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby Paddan1000 » 2012-7-03 @ 22:47

I bought this 256 MB IDE Flash module from Dealextreme in Hong Kong:
http://www.dealextreme.com/p/40-pin-ide ... 804?item=6

Too bad it didn't work with my 486. It's recognized by the BIOS, but the computer gives an error message at boot and refuses to initialize the flash module as a disk.

I'll try it with a Pentium at some other point.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby Markk » 2012-7-03 @ 23:18

If you boot from a bootdisk, is then the flash disk accessible, but it just doesn't boot from it? If so, you should try the clearhdd utility. I've atteched it here :
http://www.vogons.org/viewtopic.php?t=27285
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby Paddan1000 » 2012-7-04 @ 18:32

I couldn't use it with another disk since it has a female connector and my motherboard only has one male IDE-socket. I don't have an IDE cable with a male connector, so the Flash Disk had to be connected directly into the socket on the motherboard with no option of adding a slave device.

I tried booting with a MS-DOS floppy boot disk, but the Flash Device was still not recognized.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby nforce4max » 2012-7-04 @ 19:33

What model is the card and what cf adapter are you using it with? Not all adapters are created equal.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby Great Hierophant » 2012-7-04 @ 20:48

I currently use a SanDisk Ultra II 1.0GB Flash Card, and it works beautifully with DOS and vintage systems.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby Markk » 2012-7-05 @ 01:38

Paddan1000 wrote:I tried booting with a MS-DOS floppy boot disk, but the Flash Device was still not recognized.


Perhaps a silly question, but did you use FDISK?
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby Paddan1000 » 2012-7-05 @ 14:47

I didn't use FDISK, since the computer had no other disk from which I could run programs. I just booted with the MS-DOS installation disk and it said that no hard drives were recognized.
I did not use a CF card with adapter. I used the dedicated IDE Flash Disk in my link from DealExtreme.
My motherboard has always been very picky with what drives it would accept, so for now I have gone back to the old hard drive that at least works. I will put the Flash Disk in a Pentium, next time I visit my basement.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby Markk » 2012-7-05 @ 17:05

Well you should get an MS-DOS bootdisk with FDISK and run it first and partition the flash disk. If it isn't partitioned or even if it has a FAT32 partition and you're using DOS version up to 6.22, then it's normal for DOS not to recognize the disk. I suppose you get the "Invalid Drive Specification" message.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby megatron-uk » 2012-7-05 @ 17:13

Alternatively, exit out of the DOS 6.22 install routine (F3 does it, I think), and just run fdisk from the floppy.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby sliderider » 2012-7-05 @ 20:11

Wouldn't it be better to run Windows from a regular hard drive and only use the CF for file storage? The swap file is going to destroy a CF drive if it gets read and written to a lot.
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Re: IDE to Compact Flash as MS-DOS boot drive.

Postby SquallStrife » 2012-7-05 @ 21:45

DonutKing wrote:Look for Ontrack Dynamic Drive Overlay software, this should allow you to boot with larger drives. I've successfully used this to boot a 2GB CF card on a 486.


There are a handful of driver overlay type utilities on VogonsDrivers.

I mirrored them from http://members.shaw.ca/rinocanada/hdutils.htm
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