echadez@isis.cs.du.edu (Edward Vincent Chadez) (05/24/91)
(advance apologies to Steve Worley, who says I should just by an Amiga3000) I have some rudimentary questions regarding the Mega-Midget Racer (from CSA). Even more basic are my questions on the MMU. First of all, what function does the MMU accomplish? I realize that to use Dave's SetCPU program, an MMU is required. Which brings me to my second question, what __exactly__ does SetCPU do?? I know only of the feature which allows the operating system to be moved to 32-bit ram. Finally, is static ram required to perform the latter function?? As far as my MMR questions (which I believe should be directed to c.s.a. marketplace) what percentage is the compatibality base with other peripherals?? Are there known incompatiablities? And finally, what risks would I be taking trying to run a 16Mhz MC68881 as a coprocessor to a 20Mhz or 33Mhz MC68030?? The answer I got from CSA was that it "was not recommended" but the operator hinted that it could be done. Please understand that this would not be a final configuration of the board, but rather an intermediate function until a 33Mhz or 50Mhz FPU could be purchased. Thank you in advance for your answers. And again, apologies to Steve, who has told me to save my pennies for an Amiga3000. Edward Chadez, Amiga500 owner. -- ---//---------------------------------------------------------------------- \X/ echadez@isis.cs.du.edu Edward Chadez Amiga500-------------------------------------------------------------------
daveh@cbmvax.commodore.com (Dave Haynie) (05/29/91)
In article <1991May23.194235.5616@mnemosyne.cs.du.edu> echadez@isis.cs.du.edu (Edward Vincent Chadez) writes: >I have some rudimentary questions regarding the Mega-Midget Racer (from >CSA). Even more basic are my questions on the MMU. First of all, >what function does the MMU accomplish? An MMU provides a programmable mapping function between a CPU and main memory. This is used to set up translations between a processor's memory address (the virtual address) and the hardware's memory address (the physical address). Along with a translation, various protections can be applied. This is most often used to support virtual and protected memory systems. >I realize that to use Dave's SetCPU program, an MMU is required. To use all the SetCPU function, you need an MMU. SetCPU will still do CPU IDs and other things without it, but it won't let you run alternate KickStarts. >Which brings me to my second question, what __exactly__ does SetCPU do?? I >know only of the feature which allows the operating system to be moved to >32-bit ram. SetCPU sets up the MMU, if available, to translate a chunk of memory to ROM space. This lets it load either a copy of your ROM, or a disk image, into RAM and use it as ROM. This lets the user run with a faster ROM on full 32 bit machines and also run different version of the ROMed OS. >Finally, is static ram required to perform the latter function?? No. >And finally, what risks would I be taking trying to run a 16Mhz MC68881 >as a coprocessor to a 20Mhz or 33Mhz MC68030?? As long as you have a 16MHz clock to go with it, it should work. If you're clocking a 16MHz 68881 with a faster clock, don't expect it to work. If the FPU interface is done right, it should work with a CPU going as much as twice as fast as the FPU clock, according to what I recall from Motorola's notes on the subject. -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "That's me in the corner, that's me in the spotlight" -R.E.M.