[Coco] Read coco disks on a PC
John E. Malmberg
wb8tyw at qsl.net
Fri Mar 16 08:22:32 EDT 2012
On 3/15/2012 11:28 PM, Darren A wrote:
> On Thu, Mar 15, 2012 at 9:18 PM, John E. Malmberg wrote:
>> As I stated before:
>> The buffers are fixed in memory for Disk Basic.
>> The DISK IO routines will read all 512 bytes first into the disk buffer and
>> then overrun into the verify buffer.
>> But when the ROM routines try to use the data, they will only read the first
>> 256 bytes from the disk buffer.
> Not all operations in disk basic go through the primary buffer at $0600.
> Open data files have their own separate buffers and operations like
> COPY and BACKUP use free memory to load in multiple sectors.
> Overrunning in these cases could corrupt the disk management
> structures, the basic program or the stack.
It has been a while since I looked at the dissassembly listing of the
Disk Basic ROMs, but from what I remember, there was only one set of
routines that did the sector reads/writes and they were hard coded to
use a specific area of RAM for their buffer.
This program would also be special purpose for data interchange, not a
solution for general use of 512 byte formatted floppies with Disk Basic.
Personal Opinion Only
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