TEMPTED TO BUY the Mini Megi Chip

[MelbourneBen]

Save2600: You mentioned that its possible for the NTSC version of the mini mega to work on PAL A2000's, how is this possible? Is the jumper you speak off on the A2000 motherboard or the mini mega itself?

[nubbins]

I'm fairly new to this whole thing, but the 2 meg of chip ram solved 90% of my WHDLoad game troubles. Was well worth it to me.

Oh yeah, my stock A2000 only had 512K with an 8370 Agnus, that's why the 2MB helped my games so much. Told ya I was new.

[barney]

I always thought that if your chip mem got used up, you would default to your surplus fast ram.  Is this incorrect?

[Matt_H]

I always thought that if your chip mem got used up, you would default to your surplus fast ram.  Is this incorrect?

It's the other way around.

[save2600]

Save2600: You mentioned that its possible for the NTSC version of the mini mega to work on PAL A2000's, how is this possible? Is the jumper you speak off on the A2000 motherboard or the mini mega itself?

Jumper is on the A2000's mobo (JP102). There are no jumpers on the MegaChip. Reading the BBOAH, they make mention that the 8375 Agnus does not "switch" and that they made separate NTSC/PAL versions. Hmm... is that to say that perhaps, you cannot boot natively in one mode or the other? I can verify this tomorrow - but I think something's wrong here. I know for a fact that the 8375 can indeed switch modes through software on the fly. Software such as Degrader for instance.

[Xanxi]

Jumper is on the A2000's mobo (JP102). There are no jumpers on the MegaChip. Reading the BBOAH, they make mention that the 8375 Agnus does not "switch" and that they made separate NTSC/PAL versions. Hmm... is that to say that perhaps, you cannot boot natively in one mode or the other? I can verify this tomorrow - but I think something's wrong here. I know for a fact that the 8375 can indeed switch modes through software on the fly. Software such as Degrader for instance.

My PAL A2000 with NTSC Megichip is working NTSC.
However, using the early startup menu, it is possible to select PAL and then it works PAL until the next reboot.

[save2600]

My PAL A2000 with NTSC Megichip is working NTSC.
However, using the early startup menu, it is possible to select PAL and then it works PAL until the next reboot.

Oh - are you saying that JP102 is in PAL mode, but the 8375 ignores that and forces NTSC anyway?

[Xanxi]

Oh - are you saying that JP102 is in PAL mode, but the 8375 ignores that and forces NTSC anyway?

Yes, unless i check PAL mode in the early startup-menu.
I have searched for years for an Agnus 318069-10 (PAL) to replace the 318069-11 (NTSC) of my megichip but i have only found other 8375 Agnus not suitable for this expansion.
I am pretty sure that it all depends of the Agnus on the Megichip.
According to BBoAH:

Agnus (512K)     8361     252125-01     A1000 (NTSC), A2000A (NTSC)
Agnus (512K)    8361 R3       
Agnus (512K)    8367    252362-01    A1000 (PAL), A2000A (PAL)
Agnus (512K)    8370    318070-01    A500 (NTSC), A2000 (NTSC)
Agnus (512K)    8371    318071-01    A500 (PAL), A2000 (PAL)
Agnus (1MB)    8372A    318069-02    A500 (PAL), A2000 (PAL/NTSC)
Agnus (1MB)    8372A    318069-029    A500 (PAL), A2000 (PAL/NTSC)
Agnus (2MB)    8372AB    318069-03    A3000 (PAL), A3000T (PAL) (came after 8375B)
Agnus (2MB)    8372AB    318069-039    A3000 (NTSC)
Agnus (2MB)    8372B    318069-03    MegAChip (NTSC)
Agnus (2MB)    8375 R0    318069-18    A500+ (PAL), A600 (PAL)
Agnus (2MB)    8375    318069-10    A600 (PAL)
Agnus (2MB)    8375 R2    318069-10    A500+ (PAL), A600 (PAL)
Agnus (2MB)    8375    318069-11    A600 (NTSC), MegAChip (NTSC), Mini Megi Chip (NTSC)
Agnus (2MB)    8375 R2    318069-11    Mini Mega Chip (NTSC)
Agnus (2MB)    8375    318069-17    A500 (NTSC), A2000 (NTSC)
Agnus (2MB)    8375    318069-19    A3000 (NTSC), A3000T (NTSC)
Agnus (2MB)    8375    390544-01    A500+ (PAL), A600 (PAL)
Agnus (2MB)    8375    390544-02    A500+ (NTSC), A600 (NTSC)

[save2600]

For the European and U.K. members, why are you waiting years for a PAL 8375 when it looks like you could just purchase an A500+ and take it out of there?

[AmiDude]

For the European and U.K. members, why are you waiting years for a PAL 8375 when it looks like you could just purchase an A500+ and take it out of there?

Looks like the Mini Megi Chip from AmigaKit has no socket. The Agnus is soldered directly to the board, so no quick exchange possible. What a shame...

[Xanxi]

For the European and U.K. members, why are you waiting years for a PAL 8375 when it looks like you could just purchase an A500+ and take it out of there?

In fact i have tried the Agnus from my A500 Plus and the one from another dead A500 Plus, both of them turned to be 8375 390544-01, and none worked in the Megichip. It can boot but suffers major graphic glitches.
I have read somewhere that all Agnuses are not pin compatible.
Thus, i believe that xxx-11 should be swapable for xxx-10 only.

[barney]

It's the other way around.

So in my case, how would this megi chip help me?  I have 20MB fast ram and 1MB of chip RAM.  If the computer uses the Fast Ram First, since I have 20MB, I should never run out.  Is the extra 1MB of chip ram going to really benefit me with all the Fast Ram I have installed?

[marcfrick2112]

Barney, I think you don't quite understand the concept of Chip vs. Fast RAM. Chip RAM is used by the custom chips (Agnus,Denise,Paula) OK, if you run out of fast RAM, the system will use the slower chip ram, but the custom chips can use ONLY chip RAM, at least directly* .... So, if you ever run out of chip ram when it's needed, something will go amok.

*Some clever programs can store e.g. ,sound samples in fast Ram until they are needed, to minimize the chip ram usage. (EaglePlayer) Or, some graphics programs might keep only 2 frames of an .ANIM in chip ram, and leave the rest in fast ram, until needed. (DPaint5, I think?) BUT, when that graphics/sound data is needed, it has to be in chip ram.

So, that's why more WHDLoad games run, Worms is playable, etc. when you have that extra 1MB chip ram.

So you have 20MB fast ram and 'should never run out' .... :lol: Well, depends on what you do with your miggy.... I have a single Lightwave scene that requires ~128MB just to load. :roflmao:

[barney]

Ok, I have a better idea how memory works.  Thanks.

Barney