Dietmar Posted April 27 Author Share Posted April 27 (edited) @user57 CPUID is really a lot of stuff, see at this https://www.sandpile.org/x86/cpuid.htm Yepp, the aim can be, to set all values correct for the 486 AMD 133 MHZ cpu, Am5x86, and with a fake bit for the CMPXCHG8B. This 486 cpu is cheap, has 16kB cache and can be overclocked to 160..(200) MHZ Dietmar PS: I get 486 cpu's to run stable XP SP3: AMD 100 MHZ and AMD 133 MHZ. Only install of XP SP3 for this cpu's is not so easy. Edited April 27 by Dietmar Link to comment Share on other sites More sharing options...
Dietmar Posted April 27 Author Share Posted April 27 (edited) May be, that the check for the 9th bit in EDX for the present of CMPXCHG8B on a cpu can be faked via this Original test edx, 100h == F7 C2 00 01 00 00 replaced with or edx, 100h == 81 CA 00 01 00 00 It does not change any other in EDX, it just sets this 9th bit for CMPXCHG8B in EDX and the ZeroFlag behaves after this operation in both identically Dietmar Edited April 27 by Dietmar Link to comment Share on other sites More sharing options...
Dietmar Posted April 27 Author Share Posted April 27 (edited) Problem is, that we have only 6 byte for all. May be this bts edx, 8 ; Set the 9th bit in EDX and update the zero flag == 0f ba ea 08 test edx, edx ; Test the value of EDX against itself to clear the zero flag == 85 d2 So, always the 9th bit in EDX will be set, no matter if it was set already or not. And the test edx, edx makes sure, that the zeroflag is cleared. No other value in EAX, EBX, ECX, EDX is disturbed from this hack waaoh Dietmar Edited April 27 by Dietmar Link to comment Share on other sites More sharing options...
user57 Posted April 27 Share Posted April 27 well thats why i came up with the idea to use a older cpu to have the most of the results if some dont understand whats going on: the disassembly instruction code is useally shown with 2 methods: method 1 : hexadecimal the instruction set goes like this: (instead of 12345678 or 87654321) it go useally like this: 21435687 (memory storeage) for instruction it useally go like this : 12345678 to (real) 78563412 the disassembler dont show you this on the bit code therefore hex 00 01 translate to 0100 what is bit 9 (or classical if you have the 0 its 0 + 8 (9) bit 8 ) (because bit 1 has name bit 0 (and it still has 9 numbers))) thats why dietmar made it correct "test edx, 100h == F7 C2 00 01 00 00" and "or edx, 100h == 81 CA 00 01 00 00" dietmar pointed out that he has a cache problem actually that raise questions , the cpu dietmar use dont got that command but the OS (winxp) might have used up a cache setting, that CPUID command if present holds cache information i do not know how that interacts with the RAM memory - maybe thats some work for the WRK but i do not want to study the function Link to comment Share on other sites More sharing options...
Dietmar Posted April 27 Author Share Posted April 27 (edited) It workkkkkkkkkkkkkkkkkkkkkkkkkkkkssssssssssssssssssssssss Just now I am installing XP SP3 via CD on an AMD 486 100MHZ cpu Dietmar EDIT: But 486 compi reboots at the place, Windows is starting, when the harddisk should be seen.. EDIT2: Rom also was not build in one day. So, for today it is a nice result to overcome the CMPXCHG8B check in XP. Here are all my files until now for 486 XP SP3 boot and install https://ufile.io/7bgj5rv1 Edited April 27 by Dietmar Link to comment Share on other sites More sharing options...
Dietmar Posted April 27 Author Share Posted April 27 I think, that the reboot of the 486 compi during Setup happens, because CPUID gives values in all those registers, which tell Setup, that it is an unsupported cpu. The same happened when using a ready IDE install and can be overcome only with the nice hack from @roytam1 against Bsod 0x0000005D, Bug Check UNSUPPORTED_PROCESSOR. May be a working solution would be, to fake the 486 cpu with the CPUID settings of the Intel Overdrive 486 cpu podp5v83. But this needs to be checked careful. Anyway I get stable XP SP3 on 2 different Amd 486 cpu's, 100 MHZ and 133 MHZ. With updating the Cache to 1024 KB, may be, that XP uses all the memory and then it will be much faster Dietmar Link to comment Share on other sites More sharing options...
Cixert Posted April 27 Share Posted April 27 (edited) Have you tried the HAL "Standard Equip with C-Step i486"? If you press F5 when starting the Windows XP installation CD, when it says press F6 to install hard drive drivers, a menu appears after a few seconds to choose the HAL layer and one of the options is that, if press F5. I am not very clear if this HAL is for a review of Intel 80486 processors or refers to other processors. Edited April 27 by Cixert Link to comment Share on other sites More sharing options...
ProgramHacker Posted April 28 Share Posted April 28 7 hours ago, Cixert said: Have you tried the HAL "Standard Equip with C-Step i486"? If you press F5 when starting the Windows XP installation CD, when it says press F6 to install hard drive drivers, a menu appears after a few seconds to choose the HAL layer and one of the options is that, if press F5. I am not very clear if this HAL is for a review of Intel 80486 processors or refers to other processors. I tried it on an emulated 486, and it is laggy as hell even though it sort of support 486. Also I tried it on Pentium OverDrive 486 83mhz and it's not a fun experience. (86box) Link to comment Share on other sites More sharing options...
UCyborg Posted April 28 Share Posted April 28 I ran XP on a 2 GHz Celeron machine back in the day and it was kinda mediocre. Link to comment Share on other sites More sharing options...
Dietmar Posted April 28 Author Share Posted April 28 @Cixert Yes, I try also the 486-step3 hal.dll. Same reboot until now. @ProgramHacker With 256 MB cached ram and 160 MHZ, you can work with XP SP3 on a 486 cpu. It is still slow but enough for easy tasks. For me it is just fun as much as possible, to understand XP much better and how to speed it up Dietmar Link to comment Share on other sites More sharing options...
Dietmar Posted April 28 Author Share Posted April 28 Here is the working XP SP3 for 486 cpu. It also contains in an extra folder all the for 486 modded files. It is after install in TXT-Setup before first reboot. I tested it on an Amd 133 -p75 cpu. As CD I use my german VL xp.iso with XP SP3 Dietmar https://ufile.io/upxbmmse Link to comment Share on other sites More sharing options...
Dietmar Posted April 28 Author Share Posted April 28 Here is the source for the 486 fun above Dietmar https://ufile.io/i3j8idk7 Link to comment Share on other sites More sharing options...
ProgramHacker Posted April 28 Share Posted April 28 (edited) You can improve performance much better with MicroXP designed by experience. The iso file is 63MB, so it would fit on 128MB usb flash drive or minidisc (aka mini cd-rom). The link for this is here https://archive.org/details/ListOfEXPer1enceMicroXPTinyXPVersionsApr2018 and there's the ISO that is more than 100MB https://archive.org/details/MicroXP-0.82/MicroXP Screenshot 3.png I think you should try it and see if it works Edited April 28 by ProgramHacker Additional info Link to comment Share on other sites More sharing options...
Dietmar Posted April 28 Author Share Posted April 28 After a new, full install of XP SP3 on a 486 cpu, I get a boottime from less than 2 min. Now XP uses full 256MB ram, cached with 1024 Cache memory. The load of the cpu goes down to 35%, when doing nothing. With this XP you can work, oh..soso much fun Dietmar 1 Link to comment Share on other sites More sharing options...
Dietmar Posted April 28 Author Share Posted April 28 Full working XP SP3 for any 486 cpu, good luck Dietmar https://ufile.io/j52nyg24 Link to comment Share on other sites More sharing options...
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