Commodore 128 Programmer's Reference Manual page 502

492 COMMODORE 128
The effective sector is then translated to provide a skew that speeds up operations.
The skew is used only with the new larger format. A different skew table is used for
each region of the disk.
The third Commodore format is a GCR double-sided format. The disk is treated as
1276 sectors of data with a track offset of 0. Side 1 is used first; then side 2 is used.
u
NOTE: This is not the usual way to handle a two-sided disk; however,
allocating the disk in this manner, the user with a 1541 may still be able
to read data written at the start of a two-sided disk.
The third Commodore format and all MFM formats require that the user have the
new 1571 disk drive. This disk drive supports both single- and double-sided diskettes
and both the Commodore GCR and industry standard MFM data coding formats.
The following table summarizes 1541/1571 disk drive capabilities with regard to
the various disk formats.
0
0
u
DISK FORMAT
C64 GCR
single-sided
C128 GCR
single-sided
C128 GCR
double-sided
MFM
format
1541 DRIVE
J
J
1571 DRIVE
J
J
y
1J
C64 CP/M DISK FORMAT
(SINGLE-SIDED)
This format, shown in Figure 14-2, is provided to allow the user to read/write files
created using the C64 CP/M 2.2 cartridge. (However, do not use the CP/M 2.2 cartridge
with the C128.) Notice the unused space in this format.