On Thu, Jan 27, 2011 at 9:34 AM, Anders Carlsson <anders.carlsson@sfks.se> wrote: > Peter Krefting wrote: > >>> Also in this case the DC "knows" it deals with a 5 or 7.5 MB hard disk. >>> For example, the number of sectors/track is hard coded to 20. $20 - 32 sectors of 256 bytes (the "standard" PC formatting of the day was 17 sectors of 512 bytes) >> That helps. It also makes it harder to replace the disk later... Without changing the ROMs, yes, but the code for that was sleuthed out some time ago - there's one I/O bit that's used to determine 4 heads vs 6 heads. The rest of the parameters are in a table in ROM (or coded as constants). > Fortunately in this case, the 5 MB Tandon 602S found in a D9060 is to most > part possible to replace with a 20 MB (?) Seagate ST-225. 21.4MB technically, but, yes, 20MB (615 cylinders, 4 heads, 17 sectors of 512 bytes or 32 sectors of 256 bytes) > However due to the > hard coded addressing, only 1/4 of the latter disk will be in use. I think Yes. The requests won't go past the number of cylinders in the TM602S, so 75% of the surfaces go unused. > the same holds true for the 7.5 MB Tandon 603S but it requires a ST-231 or > such. Yes, the ST-251 (nominally 40MB). There are two versions, the ST251 uses a stepper motor with a seek time of 65ms (same as ST225), and the ST-251-1 which uses a voice coil and has a faster seek time (40ms? 25ms?) but is otherwise equivalent. > Actually one of the persons who had expressed an interest in a D9060 decided > to not buy it from me when I announced it contained a ST-225 rather than the > original Tandon drive. I suppose it is important if you want it for your > collection and not so much for using it. There are folks on both sides of that - some want an original artifact, others just want a working drive and don't care what's in the box. -ethan Message was sent through the cbm-hackers mailing listReceived on 2011-01-27 15:00:31
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