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Intel 8086 - how large harddrives are supported? (Amstrad PC1640 + XT-CF-LITE 4)

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First post, by perhenden

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The harddrive in my old PC1640 needs replacement, and I'm not sure which CF cards will work with the CompactFlash adapter for XT-IDE I bought.

My guess is that large cards , above 32MB and UDMA-enabled cards will not work. New/long-life cards within those specs may be hard to find or expensive.
Perhaps the XT-CF-LITE bios enables support for larger drives?

The XT-CF-lite FAQ says to make sure the card supports 8-bit transfer mode, and that most cards do, otherwise I can't find information on which cards are supported.
The CF spec requires that all compliant cards support 8-bit transfers in True-IDE mode, so hopefully that requirement will be easy to meet.

Recommendations for Compact Flash cards for this old 8086? Did you get a card larger than 32MB to work?

Reply 1 of 2, by derSammler

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The supported capacity depends on the hard disk BIOS and the version of DOS used. The CPU and/or architecture of the PC has no relevance. With XT-IDE, you can easily use very large cards with later versions of DOS.

Reply 2 of 2, by perhenden

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Thanks! I found that MS-DOS 3.2 and Dos plus 1.x, which the PC1640 installation media contains, supports drives up to 32MB. Later versions support larger drives/partitions, up to 2GB, with FreeDos having a theoretical limit of 2TB (!).

I learned that the original CHS addressing (on IBM PC) is using a max of 1024 cylinders, 16 heads, 63 sectors,
which maxes out for a maximum of 1024*16*63*(sector size=512)/(2**20) = 504 MB, or 528 MiB.
I chose the size 512MiB (=488MB), to be within the limit of 504MB. There are ways to work around this limit, I read.

Also, I noticed there are a couple of bundle deals on ebay, with CF-card + XT-IDE adapter, and they use CISCO Industrial Grade CompactFlash Cards, so I bought one of those.

EDIT: updated with more information, for possible future use by others in the same situation.

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