Help identifying replacement chip for Outrun

DeLuSioNaL29

DeLuSioNaL29

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Hi all,

I'm working on de-converting a Turbo Outrun to a vanilla Outrun. I'm documenting the process here: https://forums.arcade-museum.com/showpost.php?p=3546664&postcount=5

There are 4 things required:
1) CPU (I have this)
2) M27C512 EPROMS (I have this)
3) M27C256 EPROMS (I have this)
4) 1MB (Part ?) EPROM or Mask ROM. <--- NEEDED

However, I can't seem to find item # 4 above anywhere (or the EPROM equivalent). (pic below)
Here are the markings on the chip: Sega MPR-12367 T40 (8909KX). 28 pins.

Any ideas? Thanks in advance!

Jason
 

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Schematics are your friend - that ROM is probably a LH531000 which uses the usual mask rom pinout.

However, the schematics suggest there is a jumper or solder link on the video board so that you can use regular eproms instead. You have the board with all the empty sockets right? You should be able to fill them with 20 27c512's instead of 10 LH531000's.
 
Thanks for the lead, I just PM'd him to check. It doesn't look like a drop in replacement though. And I have a ton of chips to burn so I'll need something plug and play.

Fingers crossed!

P.S. - I'm surprised no one has encountered this problem before. I've seen a couple other outrun "de-conversions" but none have any details on burning the roms.

Thanks again!

Jason
 
tendril said:
Schematics are your friend - that ROM is probably a LH531000 which uses the usual mask rom pinout.

However, the schematics suggest there is a jumper or solder link on the video board so that you can use regular eproms instead. You have the board with all the empty sockets right? You should be able to fill them with 20 27c512's instead of 10 LH531000's.
Click to expand...
Almost... The roms for the 1mb chips will not burn to the small 512k chips. The rom data gets truncated when you attempt to do this on the programmer on the PC.
 
DeLuSioNaL29 said:
I may have found something. I searched for the term "128k x 8 in 28 pin" and found this on E-bay. Not exactly erasable EPPROMS, but One Time Programming chips could work too.

http://www.ebay.com/itm/Lot-of-14-N...128K-x-8-16KiB-28-pin-OTP-27C128/151425151931

I'm going to order some and report back. Hopefully they will work and I can update the other topic for historical purposes.

J
Click to expand...

The 28 pin MASK ROMs are 1Mbit devices with non-JEDEC pinout.It's impossible nowadays to find blank ones (although I have seen some UV erasable Toshiba TC531000 on some Rastan boards).Then, most of them are etched directly in factory (data are injected during manufaturing so they are not programmed)
So, the are your options:

-Use 27C1000 (or 27C301) device, they are 32 pin but its pinout is the same of the 28 pin MASK ROM, the unused pins must be tied to VCC

-Use 27C010, they are 32 pin too but with JEDEC pinout (pin 2 and 24 swapped compared to 27C1000) so you have to adapt them

-Use an adapter from a TSOP 1Mbit flash ROM to DIL package

In the first two cases, refers to this repair log for using 27C1000 or 27C010:

http://www.jammarcade.net/rastan-repair-log-3/

For the latter, read this article:

http://blog.system11.org/?p=1871

P.S.
A 27C128 is a 16K x 8-bit device and not 128K x 8-bit so not suitable for your purpose.
 
Last edited:
DeLuSioNaL29 said:
Almost... The roms for the 1mb chips will not burn to the small 512k chips. The rom data gets truncated when you attempt to do this on the programmer on the PC.
Click to expand...

Well sure, you have to cut the source into upper and lower halves - how else will you fill 20 27c512 from 10 source files? :)

Your ebay link is 128kiloBITS, not bytes, as the other post says, so that's a no go.
 
For anyone curious, this is why trying to adapt 32 pin ROMs to fit isn't easy on this board. No physical space. The schematics do suggest the links at R1 and R2 will allow 27c512s to be used - but you should multi-meter it to be sure.

outrun_video_pcb_partside.jpg
 
I guess perhaps I can build an adapter, but again, as tendril states, they won't fit since there is no room to expand. Maybe I can put an extra extension in the second, third and fourth rows so that it won't overlap with the chip next to it. I need to think about how I'd manage it. [That would be a clunky looking (and progressively tall) config!]

What's a good source to get adapters from (like the ones I attached to this post).

P.S. - From what I've read online: I'm still baffled as how to everyone who's "done the de-conversion" swears it was easy. I call BS! LOL!

Thanks guys for your help. Keep the suggestions coming in the meantime.

Jason
 

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Last edited:
It would be much easier and cheaper to just use 27512's.... Why wouldn't you do that? Figuring out the board strapping is not that hard, and someone here has probably already done it.
 
Any links? Board strapping yields nothing in my search.

I'm understanding the concept of splitting the roms into 2 chips, but where would they go? I'm lost.

Does sound interesting though.
 
DeLuSioNaL29 said:
Any links? Board strapping yields nothing in my search.
Click to expand...

Links? I don't know of any step-by-step guide if that's what you're looking for....
But like tendril said, the info is in the schematics (see page 11). It's not entirely clear (there are a couple comments in Japanese). But it looks like you may not have to do anything to use 27512 (besides putting them in the correct positions). For using 27256, it looks like you would remove jumper R1 (a zero ohm resistor), and jumper R2 and R3. But you really should inspect the board to be sure.
 
Board strapping
that would yeild u a perty big search
try >>rom strapping<<
all rom's have a control _enable line
it is called strapped (high through a resistor)
this "enables" the rom or rom's in question

ed
 
mattosborn said:
It's not entirely clear (there are a couple comments in Japanese). But it looks like you may not have to do anything to use 27512 (besides putting them in the correct positions).
Click to expand...


Like Matt says, it looks like jumpers are for 27c256 OR 27512/1Mb Mask
so if you're board has the mask roms, I would think it's set to the correct jumpers for 27c512.

The part I'm still unclear about is how do you split the eproms ?
If each 1Mb mask rom becomes two 27c512, how are they configured ?

IC9 (1Mb) = IC9 (512) + IC10 (512) ?
IC10 (1Mb) = IC11 (512) + IC12 (512) ?
or
IC9 (1Mb) = IC9 (512) + IC13 (512) ? ( eproms are in banks of 4 )

I tried to read the address lines on the schems, but it really was not clear .

Anyone ?

Steph
 
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