keeshu@nikhefk.uucp (Kees Huyser) (11/14/86)
I'm posting this for a friend of mine who has no netaccess : ---- Someone asked me about the ROM patch I mentioned in a net posting earlier. I dug up some information 'bout it. The ROM patch involves the Atari U7 ROM (U7 relates to the PCB name for that ROM, visible when you open the case of your ST. It's located in the lower left corner of the PCB). It appears to be that the ST ROM's double-check the track the diskarm is at, whereas the disk-controller already performed that check. So your ST is 'double-sure' it's on the right track when it performs read or write seeks. This, ofcourse, is nonsense. So clever folks somewhere in Germany found a way of defeating the double-check. They changed only one bit in the U7 ROM, which makes it much, much faster. I received my patched ROM without having to make any patches myself, but I'm pretty sure the following information is accurate. Just to be on the safe side: I have a 1040 ST with normal, legal ROM's, but I replaced the U7 with a patched EPROM. No hardware modifications are necessary, it's a clean job. Location $0CD7 (that is, ofcourse, hex) holds value $14 (also hex). When changed into $10 (hex again), the disk I/O becomes a real joy. That's it. I believe you need a 27256 EPROM to do the job. Paul Molenaar ---- Replies to the above posting can be send to me. Kees Huyser +-------------- | Kees Huyser | UUCP : keeshu@nikhefk.UUCP | {[wherever]!seismo}!mcvax!keeshu@nikhefk.UUCP | BITNET: U00212@HASARA5.BITNET | IF YOU BELIEVE DISCLAIMERS, YOU'LL BELIEVE ANYTHING! +--------------
cabbie@chinet.UUCP (Richard Andrews) (11/16/86)
In article <58@nikhefk.UUCP> keeshu@nikhefk.uucp (Kees Huyser) writes: > >Someone asked me about the ROM patch I mentioned in a net posting earlier. >I dug up some information 'bout it. > > The ROM patch involves the Atari U7 ROM (U7 relates to the PCB name for that > ROM, visible when you open the case of your ST. It's located in the lower left > corner of the PCB). > > information is accurate. Just to be on the safe side: I have a 1040 ST > with normal, legal ROM's, but I replaced the U7 with a patched EPROM. > No hardware modifications are necessary, it's a clean job. > >Location $0CD7 (that is, ofcourse, hex) holds value $14 (also hex). When >changed into $10 (hex again), the disk I/O becomes a real joy. That's it. >I believe you need a 27256 EPROM to do the job. > > After pouring over some dumps of both the rom in question and of several sections of memory I have failed to locate the bytes indicated above. I have determined that either the locations are wrong or the data above is wrong. According to what is see here on this end, U7 and U4 share the same general area of memory. U7 is mapped to $FCxxxx-L and U4 is mapped to $FCxxxx-H. It sure would be nice to have a dump of that eprom uuencoded and placed on the net. Even the first 8 or so bytes prior and after the byte to be changed would be nice. -- ******************************************************************************* Any opinions expressed above are my own. Rich Andrews They can be yours too. Please send $19.95 to.....ihnp4!chinet!cabbie *******************************************************************************