MediaWiki:Sitenotice:
2025-12-29: I have restored the wiki to a backup from the end of November. Starting in September 2025, accesses went form the 800MB-1.2GB range per month to 26GB in September, 42GB in October, and 70GB in November with most accesses originating from China. As soon as I realized what was causing all the access problems in November, I shut it down (it had reached 36GB by then) behind a password/login screen. The database had gotten corrupted, and I tried a restore from just before the spike in access but that didn't work. Thus, end of November. I still have the other daily backups so if there were any important additions in December, let me know and maybe they can be recovered. - Allen H.
Hacking Disk: Difference between revisions
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Luis46coco (talk | contribs) Created page with '{{NavHardware}} [http://www.oocities.org/theother_bob/coco_page/ccdisk00.htm From] Color Computer Floppy Drive Info Go Back Adding Floppy Drives One of the coolest things abo…' |
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[http://www.oocities.org/theother_bob/coco_page/ccdisk00.htm From] | [http://www.oocities.org/theother_bob/coco_page/ccdisk00.htm From] | ||
Color Computer Floppy Drive Info | '''Color Computer Floppy Drive Info''' | ||
Go Back | Go Back | ||
Adding Floppy Drives | '''Adding Floppy Drives''' | ||
One of the coolest things about the CoCo (IMO) is that it can use standard PC floppy drives. Unfortunately, Disk Basic (RSDOS) only uses one side, and low density of course... 35 tracks, which yields 156K per floppy. | One of the coolest things about the CoCo (IMO) is that it can use standard PC floppy drives. Unfortunately, Disk Basic (RSDOS) only uses one side, and low density of course... 35 tracks, which yields 156K per floppy. | ||
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40 and 80 track access: Pros and Cons | '''40 and 80 track access: Pros and Cons''' | ||
Okay, let me try to make a long story short... CoCo disk tracks are divided into two granules. There are 35 tracks, minus one for the directory (track 17). This gives us 68 granules on a newly formatted floppy, all kept track of in the GAT (Granule Allocation Table). Changing the number of tracks the CoCo uses means changing the size of the GAT. 40 or 80 track drives would have 78 or 158 granules, respectively. | Okay, let me try to make a long story short... CoCo disk tracks are divided into two granules. There are 35 tracks, minus one for the directory (track 17). This gives us 68 granules on a newly formatted floppy, all kept track of in the GAT (Granule Allocation Table). Changing the number of tracks the CoCo uses means changing the size of the GAT. 40 or 80 track drives would have 78 or 158 granules, respectively. | ||
Since RS-DOS is designed to handle up to 4 drives, there are 4 areas in RAM set aside for the 4 GATs. One byte per granule plus 6 bytes overhead per drive equals 74 bytes per drive, or 296 bytes total (for GAT storage). Some quick math shows us that only three 40 track or one (gasp!) 80 track can fit in the alloted space! (remember, in RS-DOS each side counts as a separate drive, so 2 double-sided drives equals 4 drives to RS-DOS.) | Since RS-DOS is designed to handle up to 4 drives, there are 4 areas in RAM set aside for the 4 GATs. One byte per granule plus 6 bytes overhead per drive equals 74 bytes per drive, or 296 bytes total (for GAT storage). Some quick math shows us that only three 40 track or one (gasp!) 80 track can fit in the alloted space! (remember, in RS-DOS each side counts as a separate drive, so 2 double-sided drives equals 4 drives to RS-DOS.) | ||
The good news... | |||
'''The good news...''' | |||
The good news is that you can patch Disk Basic to relocate the GAT. The patch program 4080DSK.BAS and a 40 to 35 track disk fixer DFIX35.BAS are included on the Color FOG disk image. | The good news is that you can patch Disk Basic to relocate the GAT. The patch program 4080DSK.BAS and a 40 to 35 track disk fixer DFIX35.BAS are included on the Color FOG disk image. | ||
These programs originally appeared in The Rainbow, July 1985. Copyright 1985 Colin J. Stearman. Colin, I hope you see this and are amazed that someone still finds this stuff useful and/or interesting. | These programs originally appeared in The Rainbow, July 1985. Copyright 1985 Colin J. Stearman. Colin, I hope you see this and are amazed that someone still finds this stuff useful and/or interesting. | ||
And the BAD news... | '''And the BAD news...''' | ||
the bad news is that you lose compatibility. If you modify RS-DOS for 80 track drives, you will not be able to read or write your 35 or 40 track disks. A 40 track setup will read and write your 35 track disks. If you wish to use your 40 track formatted floppies in a 35 track system you should run the DFIX35.BAS program immediately after formatting a disk to prevent data being saved on the last 5 tracks or else the disks may contain data that cannot be read by a stock CoCo. | the bad news is that you lose compatibility. If you modify RS-DOS for 80 track drives, you will not be able to read or write your 35 or 40 track disks. A 40 track setup will read and write your 35 track disks. If you wish to use your 40 track formatted floppies in a 35 track system you should run the DFIX35.BAS program immediately after formatting a disk to prevent data being saved on the last 5 tracks or else the disks may contain data that cannot be read by a stock CoCo. | ||