pbrody@udenva.UUCP (Paul Brody ) (08/21/87)
I am asking this question for a programmer friend of mine who is currently working on a new piece of software for the Amiga. He is having some trouble with getting access to the KS1.2 protected ram. Question: Where, on the KS1.2 disk, is the code that writes to the memory, (F80000 being the believed location in memory) that write protects the KS1.2 ram ? The purpose being to put some NOPS on the KS1.2 disk that will disable the code and consequently leave the KS1.2 ram unprotected. Question #2: What is the purpose of the memory overlay bit on the 8520 chip ? When he tries to use it he gets a Guru error of FF17, which is undocumented. Any replies on either of these two questions would be GREATLY appreciated. If there is sufficient interest in the topic I will summarize and post replies. Please send reples to: pbrody@udenva =============================================================================== || The above is not representative of the opinions of the Universtiy || || of Denver || || || || Paul Brody || || pbrody@udenva || ===============================================================================-- =============================================================================== || The above is not representative of the opinions of the Universtiy || || of Denver || || || || Paul Brody || || pbrody@udenva || ===============================================================================
cmcmanis%pepper@Sun.COM (Chuck McManis) (08/24/87)
In article <4119@udenva.UUCP> pbrody@udenva.UUCP (Paul Brody ) writes: > I am asking this question for a programmer friend of mine who is > currently working on a new piece of software for the Amiga. He is having ^^^ > some trouble with getting access to the KS1.2 protected ram. > Question: > Where, on the KS1.2 disk, is the code that writes to the memory, (F80000 > being the believed location in memory) that write protects the KS1.2 ram ? > The purpose being to put some NOPS on the KS1.2 disk that will disable the > code and consequently leave the KS1.2 ram unprotected. First the answer to this question can be ascertained by studying KS and the Commodore schematics but the 64K question is Why?!!? A) If it is new software why target a machine that will be only half the installed base by christmas? KS is in ROM on the 500, and 2000. Don't you want these folks to buy your programs too? Also unless you recompute the Kickstart checksum you will find your machine dieing with a 'ROM Failure' I believe. > Please send reples to: > pbrody@udenva Sorry Paul, but this is one of those things that it is pretty silly to put into a released product. I can understand hacking at it to figure out the machine, just keep it out of any products I might pay money for and find out that it doesn't work on my machine. --Chuck McManis uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com These opinions are my own and no one elses, but you knew that didn't you.
grr@cbmvax.UUCP (George Robbins) (09/05/87)
In article <4119@udenva.UUCP> pbrody@udenva.UUCP (Paul Brody ) writes: > > What is the purpose of the memory overlay bit on the 8520 chip ? When he > tries to use it he gets a Guru error of FF17, which is undocumented. The OVL or overlay bit is used to map ROM over the video RAM starting at address 0 to allow the 68000 to find it's way into the normal ROM location. It is set high by the hardware reset and then the software sets it low right after it jumps to the normal ROM address range. It doens't make too much sense for a program to mess with this bit. Either you have to already be executing out of ROM, or you need to be executing code in RAM copatible with that in the ROM at the corresponding addresses when the floor drops out from under you. -- George Robbins - now working for, uucp: {ihnp4|seismo|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@seismo.css.GOV Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)