rcollins@altos86.Altos.COM (Robert Collins) (05/14/91)
In article <107840001@hpcuhc.cup.hp.com> you write: > >(Yes, I know that the answer might be different for different clones, but > if I can find out the answer for at least one clone, that gives me a > starting point. And you never know, a de facto standard might have arisen.) > Hello, I'm a BIOS programmer. It's my job to program this stuff you are asking about. I don't see how knowing how to do it on ANY clone will help you. For example: * Some chip sets are addressed via an indexed/register scheme, kinda like CMOS RAM. Many chips sets use port 22h as an index, and 23h as data. The speed register within these type chip sets is always different. Some registers are write-only, some are read/write. * Some computers simply use an I/O port. In some cases, the port is R/W, other times it is W/O. * Some computers use memory mapped I/O. Memory mapped I/O are ports that are addressed by simply writing to memory. * And then there is EISA. EISA changes speed by reprogramming the 2nd interval timer chip (that doesn't exist on non-EISA machines). Counter2, Timer2 is programmed for one-shot mode. Each time the trigger occurs, the hardware asserts HOLD on the CPU for a small period of time. This simulates a speed slow down, but in reality the processor is still running at full speed. What you need to know is what chip set you are using, and how the hardware manufacturer implemented that chipset. Even though the chipset may use I/O, the designer may have used memory mapped I/O. I seriously doubt any designer would do this, as I only say this to impress upon you that you need to know what hardware you have FIRST, then proceed. There is NO defacto standard. R. Collins -- "Worship the Lord your God, and serve him only." Mat. 4:10 Robert Collins UUCP: ...!sun!altos86!rcollins HOME: (408) 225-8002 WORK: (408) 432-6200 x4356 --- "Worship the Lord your God, and serve him only." Mat. 4:10 Robert Collins UUCP: ...!sun!altos86!rcollins HOME: (408) 225-8002 WORK: (408) 432-6200 x4356 -- "Worship the Lord your God, and serve him only." Mat. 4:10 Robert Collins UUCP: ...!sun!altos86!rcollins HOME: (408) 225-8002 WORK: (408) 432-6200 x4356