Blizz 030 Mk4 - How to enable the MMU

[NovaCoder]

I ran Sysinfo last night and noticed that the MMU was not 'enabled'. Do you have to do something in the start sequence to enable it or something?

Thanks

[keropi]

strange... what are the markings on the cpu? what OS do you use? if you boot with a 3.0/3.1 floppy disk and run sysinfo, does it still say the MMU is not enabled?

[NovaCoder]

Originally Posted by keropi

strange... what are the markings on the cpu? what OS do you use? if you boot with a 3.0/3.1 floppy disk and run sysinfo, does it still say the MMU is not enabled?

Not sure what the markings are (I'm at work ) but I'm running OS 3.9

I'm pretty sure it's 'MC68030RC50C' which I think is the latest variant.

Didn't all 030's have an MMU anyway?

[rkauer]

All non-EC 030 have MMU.

Try to use this command: CPU databurst datacache fastROM.

Don't do this in 3.9! Only in 3.0/3.1!!!

[NovaCoder]

Originally Posted by rkauer

All non-EC 030 have MMU.

Try to use this command: CPU databurst datacache fastROM.

Don't do this in 3.9! Only in 3.0/3.1!!!

What happens if you do this in 3.9...does it exploded or something

Anyway, I'm running 3.9 so what's the plan

[rkauer]

Boot with a plain 3.1 disk and type the command...

Then start sysinfo again.

[adolescent]

SysInfo only shows the MMU as enabled if something is using it. No need to try to enable it, it's either there and working or not. (Try running something like Enforcer if you really must see it working.)

[NovaCoder]

Originally Posted by adolescent

SysInfo only shows the MMU as enabled if something is using it. No need to try to enable it, it's either there and working or not. (Try running something like Enforcer if you really must see it working.)

That's interesting, so the OS doesn't use it for it's own memory management. Ok, I'll try Enforcer and see what happens. I'm sure it works fine, I was just surprised to see that it wasn't being used.

[rkauer]

MMU is not for memory management! Is intended for relocating portions of it using the MMU as a "pointer".

Example: when you copy the ROM into RAM and then "tricks" the OS and programs to look in a specific address instead the original.

Another use is for controlling a "virtual memory". Never used in any Amiga OS (but some patches/programs exist).

[NovaCoder]

The official blurb.

A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware component responsible for handling accesses to memory requested by the central processing unit (CPU). Its functions include translation of virtual addresses to physical addresses (i.e., virtual memory management), memory protection, cache control, bus arbitration, and, in simpler computer architectures (especially 8-bit systems), bank switching.

Motorola 68030 Memory management unit

Thanks for all the info peoples

[Hanzu]

Originally Posted by adolescent

SysInfo only shows the MMU as enabled if something is using it. No need to try to enable it, it's either there and working or not. (Try running something like Enforcer if you really must see it working.)

Sorry for a little bit offtopic, but I was about to install Enforcer and run it, but http://de4.aminet.net/dev/debug/enforcer.readme says "Requires an MMU. On 68EC030 systems, it may think it is working even if it is not due to the fact that the missing MMU is very hard to detect. Use LawBreaker to check.

Where I get this LawBreaker from?

I also want to enable MMU but in 68030 to see it is not fake made from 68EC030.

Someone may say use WhichAmiga for that and yes I already did, but it has a known long time bug: "always report 68EC030 if 68030mmu is not in use." So I need some reliable tool to check if MMU exists and then enable it for WhichAmiga and SysInfo.

[nogginthenog]

Originally Posted by rkauer

MMU is not for memory management! Is intended for relocating portions of it using the MMU as a "pointer".

Example: when you copy the ROM into RAM and then "tricks" the OS and programs to look in a specific address instead the original.

Not entirely true. It is used for example to mark Chip-RAM as non-cacheable as the Blitter can change data in chip ram without the CPU knowing.

[Toni Wilen]

Originally Posted by Hanzu

Where I get this LawBreaker from?

It comes with enforcer archive.

But note that it is practically impossible to reliably detect if 68EC030 has bad or working MMU. At least some 68EC030's are 68030's with MMU that didn't pass all tests. Some MMU operations may fail, some MMU operations may hang the system instantly and so on.. (For example I had 68EC030 that worked perfectly fine with enforcer but instantly hung if more complex MMU software was used)

Only 68040+ non-MMU/FPU models can be detected reliably.

[Mr.Flibble]

Originally Posted by Hanzu

Sorry for a little bit offtopic, but I was about to install Enforcer and run it, but http://de4.aminet.net/dev/debug/enforcer.readme says "Requires an MMU. On 68EC030 systems, it may think it is working even if it is not due to the fact that the missing MMU is very hard to detect. Use LawBreaker to check.

Where I get this LawBreaker from?

I found it here: http://www.sinz.org/Michael.Sinz/Enf...eaker.asm.html

But it's also in the Enforcer lha package.

[hooverphonique]

Originally Posted by nogginthenog

Not entirely true. It is used for example to mark Chip-RAM as non-cacheable as the Blitter can change data in chip ram without the CPU knowing.

I don't think this is true, because that would cause problems for cpus that have cache and no mmu.. afaik, chipram is marked non-cacheable by asserting some hardware signals directly on the cpu package.

[Hanzu]

Originally Posted by Toni Wilen

It comes with enforcer archive.

But note that it is practically impossible to reliably detect if 68EC030 has bad or working MMU. At least some 68EC030's are 68030's with MMU that didn't pass all tests. Some MMU operations may fail, some MMU operations may hang the system instantly and so on.. (For example I had 68EC030 that worked perfectly fine with enforcer but instantly hung if more complex MMU software was used)

Only 68040+ non-MMU/FPU models can be detected reliably.

Thank you for this info.

I tried rkauer's advice and OS3.1 CPU command. Also noticed that just "CPU fastrom" enables MMU and "CPU nofastrom" disables it. After enabling it WhichAmiga shows CPU as MC68030 and MMU enabled. I assume same goes with Sysinfo.

I wonder if this unreliability is also why WhichAmiga or Sysinfo is not showing mask revisions for 030, like it shows for 060 (and possibly 040 too, cannot remember).

[Toni Wilen]

Originally Posted by Hanzu

I wonder if this unreliability is also why WhichAmiga or Sysinfo is not showing mask revisions for 030, like it shows for 060 (and possibly 040 too, cannot remember).

Yes. 68040 and 68060 MMU (and FPU) instructions are guaranteed to return unknown instruction exception if hardware does not support them. 68030 just tries to use possibly broken hardware. Motorola official documentation says that 68EC030 MMU instruction behavior is undefined.

68060 (and only 68060) supports PCR register that returns model type (full/EC/LC) and mask revision.

[meynaf]

I've read somewhere (but i don't remember where) the following procedure to detect an MC68EC030.

First initialize the MMU to map one page of memory onto another page as if the part was an MC68030. If the MMU instructions cause an illegal instruction, then the part is an MC68EC030. If the MMU instructions do not cause an illegal instruction, then write a flag to the mapped page. Disable the MMU and read the location with the flag. If the flag's physical address matched the logical address, the part is an MC68EC030. If the flag's physical address does not match the logical address, then the part is an MC68030.

Is this procedure reliable or does it fail on some 68EC030 ?

Originally Posted by Hanzu

I wonder if this unreliability is also why WhichAmiga or Sysinfo is not showing mask revisions for 030, like it shows for 060 (and possibly 040 too, cannot remember).

AFAIK mask revisions are impossible to get by software on 030 ; there is simply no way to do that. I've got both RC50B and RC50C ; they behave exactly the same.