Geoff Strickler ha escrito: > You would be hard pressed to clock chip a //e or //c. You would have to be > very mindful of the memory access times. Disk read/write and > paddle/joystick routines are all software timing loops. On the //c, the > serial port clock may be generated from the main CPU clock. IIRC, the video > clock may also be generated from the CPU clock.
That's right. The //c only has a 14 Mhz master oscillator from wich all timming signals (7 Mhz and 3.5 Mhz dot clocks, 2 Mhz bus clock, 1 Mhz CPU clock, etc.) are generated by the TMG (TiMming Generator) unit (a frequency divisor). Almost only components in the //c board that aren't driven by the master oscillator are the two serial ports, which need a very exact timming that can not be derivated from 14 Mhz by frequency division. I don't know the //e, but I'd bet it's the same as for the //c, except for the serial ports thing. The disk access is quite critical. In fact, both the //gs and the //c+ automatically enter a 1 Mhz mode every time a disk drive is accessed (and return to high clock speed when the access finishes). In the Apple II, it is the main processor, rather than the diskc ontroller, who times all bits in a disk access. A real pain to do in code, having to count every clock cycle of every instrucion, but it works - Woz was a genius! :-) . Greetings, Antonio Rodr�guez (Grijan) <ftp://grijan.cjb.net:21000/> -- Apple2list is sponsored by <http://lowendmac.com/> and... / Buy books, CDs, videos, and more from Amazon.com \ / <http://www.amazon.com/exec/obidos/redirect-home/lowendmac> \ Support Low End Mac <http://lowendmac.com/lists/support.html> Apple2list info: <http://lowendmac.com/lists/apple2.html> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/apple2list%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
