DP8473A (was IBM Displaywriter software?)

On 12/28/2012 05:05 PM, Fred Cisin wrote: Yes, it's annoying to be working with a WD17xx-created format without the IAM and have a 765-type FDC "go blind" during the "PLL sync" period. There was a NEC uPD7265 that omitted the IAM for so-called "Sony Mode" recording, but those are exceedingly rare. NEC has sort of a "Read Track - read multiple sectors without looking at the IDAM" command; it starts after the index and reads subsequent sectors starting at each DAM. You can have an unreadable IDAM and still recover the sector data if the DAM is readable. You also can feed the 765 a "Read Track" with a phony datalength specified. The 765 will suck up all of the data after the first DAM after the index until the transfer count is exhausted. Thus, you get gaps, AMs, headers, all "in the raw", meaning that the 765 does not resync during the transfer. Great if you're using original floppies made using a Formaster that writes an entire track in one swell foop, not so much for tracks where the sectors are written individually. The WD17xx and 27xx type controllers, OTOH, resync at every address mark during a "Read Track". Harvard Presentation Graphics used this technique to read their "HGC" stashed in the gap bytes between sectors. Also, consider implementing some of the 82078 added commands, particularly "Format and Write" (can make copying go very fast) as well as the PM functions. Personally, I'd do the board as a USB card, given the difficulty of finding ISA-equipped motherboards or dealing with the nuances of PCI/PCIE, etc. You should also be aware that Andrew has been testing prototypes of an ISA FDC that can use either the I82077AA, PC8477 or DP8473 chips. --Chuck