Framestores Only Load One Quarter of the Screen

Product: Video Toaster, Flyer

Platforms: 4000 4000T with IDE drive

Problem: When you select a Framestore to load, the top quarter loads and then the loading stops, with no error message. Saved Framestores are corrupt.

The A4000 series machines ship standard with IDE drives. Commodore modified the drive setup utility, HDToolbox, to be able setup IDE drives, but did not not change the setup defaults from SCSI drive defaults to IDE drive defaults. HDToolbox even lists the drive type as SCSI when the drive is actually IDE.

The particular SCSI setting which causes the most trouble for IDE drives is the "MaxTransfer" setting, which sets the maximum size of chunk of data that the system will try to exchange with the drive at a single pass. MaxTransfer is a size, not a speed setting. As such, when MaxTransfer is set too high, data transfer actually slows down, because communications between the host and the drive become garbled. When Maxtransfer is set properly, then the drive and the system communicate very smoothly, and much faster.

Commodore originally shipped the A4000 with Seagate ST3144A drives, which are IDE drives that can operate using the SCSI default settings, in particular the "MaxTransfer" setting, which is a figure of "0xffffff" (leading character is a zero, not a capital letter "O"). Virtually no other make/model IDE drives can do that. Most operate well with a figure of "0x1fe00" (zeros, not capital "O"s).

Note: This problem can affect users of IDE controllers made for other model Amiga computers. GVP at one time produced accelerators which had integrated IDE controllers, and Expansion Systems makes IDE controllers which work in the A2000 and A3000 systems.

See: Setting MaxTransfer