sarah-walker-pcem / arculator

Arculator
http://b-em.bbcmicro.com/arculator
GNU General Public License v2.0
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Feature request: allow disc images > 1024 cylinders #49

Open rhalkyard opened 2 weeks ago

rhalkyard commented 2 weeks ago

It appears that by default, disc images are forced to conform to ADFS' 1024 cylinder limit when they are loaded. However some filesystems (e.g. ZIDEFS with the ICS card, or Armstrong Walker IDEFS with the HCCS A3000 card in PR #47) support multiple ADFS volumes on a larger, partitioned disc.

I modified these limits in my own build of Arculator, and it seems to function as expected - with my HCCS emulation, I can carve a 2GB image up into 4 512MB partitions, like I do with a flash disc on my real A3000. Given that this is a valid use case on original hardware, would it make sense to lift these limits, or at least add an "I know this is too big for ADFS and I want it anyway" option to bypass them?

IJeffray commented 2 weeks ago

Well, ZIDEFS does not "support multiple ADFS volumes" - it supports multiple IDE targets, each with a partitioning scheme which supports up to four Filecore logical drives. Not ADFS. ADFS is not Filecore. This distinction may be important if the original intent was to be strict about ADFS's limitations - notwithstanding that RISC OS 3.1's ADFS can actually handle physical media > 512MB, though only address the first 512MB of it -- not sure about anything before RISC OS 3.1.