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Help with non booting NEO-MVH MV4 and 2 slot with lines in sprites

Thats the work ram chip that handles the lower byte of the word, which will be the 4th ram chip down. If you already replaced that chip you might verify there arent any bridges near pin 12 on the chip before replacing it again.

The ordering of those 6 ram chips on the MV4/MV6 is

video ram upper 8 bits
video ram lower 8 bits
work ram upper 8 bits
work ram lower 8 bits
backup ram lower 8 bits
backup ram upper 8 bits
 
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So if your talking about the row of SMD rams the 4th one down was never replaced but there was some touch up work done on a few pins. Ill reflow solder on all those pins. I have working rams i can replace it with if the touch up doesn't help
 
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The 68k cpu has a 16 bit data bus, but these ram chips only provide 8 bits of data. So it takes 2 ram chips to make up 16 bits of data. For each ram type (video, work, backup) one ram chip is the upper 8 bits, and the other is the lower 8 bits.
The original error was

Actual: 0002
Expected: 0000

So there was a bad bit in the lower 8 bits (4th ram chip down)

While the new error is

Actual: 4000
Expected: 0000

This time the bad bit is in the upper 8 bits (3rd ram chip down)
 
Cool just replaced that chip and no more WRAM errors.

Now i got an error saying "VRAM 32k Dead Output (Lower)"
but after a power cycle i just keep getting a VRAM error saying its expecting a value of 0000 but is getting FFFF on address 000000 continually




Thanks for the help locating these rams btw
 
So Gadget UK had a video about this 4slot and the 5814 rams should be the VRAM's but I actually already replaced these and socketed them.

I swapped the two rams and that made no difference so I replaced both of the 5814 rams again and i still got the exact same error


On one of the power cycles I got a "VRAM 32k Dead Output (Lower)" error again making that the second time that has shown up. I am concerned the graphics chip is bad.

I am gonna go ahead and reconfirm that the 2 rams get voltages
I might spend some time banging out all the traces to the VRAM's to ensure they are infact making good continuity

Let me know your thoughts
 
There are 2 sets of vram chips. The top 2 chips in the bank of 6 smd ram chips and the 2x dip ram chips under the LO rom that you are talking about. Those dip chips are often referred to as the fast vram chips as they have a much lower access time then the smd chips.

The smd chips are 256Kbit / 32Kbyte
The dip chips are 16Kbit / 2Kbyte

The error is referring to the smd chips since it says 32K, if it were the dip chips it would say 2k.
 
Got it ill take another look at those then thank you so much
 
Okay so I replaced both of these rams with ones I pulled from another MVS many moons ago.

The reason I just replaced both of them was because after taking a long hard stare at those two rams I realized when I replaced both the 32k ram and 2K ram I actually replaced the 2k with an incompatible type of ram because I misread the name on the rams. (they were BR6265's which is used for pallet ram. Its an 8k x 8 not a 32k x 8 like what the Sony chips are.)

When I pulled those 2 rams again I checked my work again and verified all the pads and traces and vias still have continuity and also to the LSPC-A0



Suffice to say I pulled out my last 2 possibly working rams and now I get an error about address line 00021B not being correct . I still have a donor 2 slot board with a ton of SMD rams that could work though.

It would be better if I could figure which of the two rams is causing this error or an explanation on how to tell in the future which address is for the upper bytes and which is for the lower bytes. That way I know exactly which chip to pull and replace instead of doing them in pairs.



Also as a result of this. The strange "characters" that were shown on the first posts picture are back (possibly because the Vram is actually some what working again LOL)

Here is a current picture for reference:
https://drive.google.com/open?id=1-hYniwLY2lM9_wKS9DDxmKXiaoycJF7i


Thank you for all your help again.
 
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GeekMan1222 said:
It would be better if I could figure which of the two rams is causing this error or an explanation on how to tell in the future which address is for the upper bytes and which is for the lower bytes. That way I know exactly which chip to pull and replace instead of doing them in pairs.
Click to expand...
Its not the address that determines the upper vs lower byte. Each address is for 16 bits of data, the upper 8 bits will be one chip and the lower 8 bits the other chip.

Your current error is:

VRAM DATA (0000)
Address: 00021B
Actual: 0080
Expected: 0000


Blue = upper byte / 8 bits
Red = lower byte / 8 bits

In this case the issue is in the lower byte / 8 bits since 80 != 00. Unfortunately the bios isn't telling you which set of vram chips (smd or dip) the error occurred in, but you can figure it out based on the address.

https://wiki.neogeodev.org/index.php?title=VRAM

VRAM addresses 0x0000 to 0x7FFF are the 32K smd chips

VRAM addresses 0x8000 to 0x87FF are the 2k dip chips

00021B falls within the 32k smd vram chips

ack said:
video ram upper 8 bits
video ram lower 8 bits
work ram upper 8 bits
work ram lower 8 bits
backup ram lower 8 bits
backup ram upper 8 bits
Click to expand...
So the error is pointing to the 2nd smd ram chip down in that set of 6 smd ram chips.

 
Wow this was beautifully illustrated and i feel kinda dumb now but now I know THANKS!!!

Ill take a look and get back with everyone here soon
 
The pair of 2KB SRAMs connected to the LSPC are pinout compatible with 6116s but are of a special type since they're very fast (35ns) and putting slower 6116s there will be bad. Just commenting so you don't overlook that detail.

The 6116 used on the sound CPU are very slow, like 100ns or something like that.
 
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