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Arkanoid 2 - graphics problem broken AND/OR missing ROM chip?


DragonsTrap

Question

Hi everyone, first (proper) post.

 

I've picked up this Arkanoid 2, and I -think- that maybe the B08-04 ROM is missing.

 

Here's the display I see at title and game demo.

ark2-title.jpgark2-demo.jpg

 

The game boots straight up; I don't think there's any sort of ROM check.

 

And here's my PCB

ark2-pcb.jpg

 

I downloaded the MAME ROM set and the B08-04 ROM chip is included there but my board doesn't have it.

The MAME ROM set didn't have the B06-XX ROM files that I labelled on my photo,

so I assume they are common to this board model or something and maybe included in some generic Taito board ROM.

 

I found this picture of the PCB online

http://www.arcade-museum.com/images/118/118124204862.jpg

and that shows the B08-04 chip in the top right corner.

 

Mine is an identical board but missing this.

I'm pretty sure I've been bullshitted by the guy I bought this from (he told me it was working fine), but I just wanted to ask

[edit: i'm now fairly sure it was an honest mistake and that he didn't know the ROM was missing, it may've fallen out somewhere]

1. Am I missing the ROM? Is it possible that there's a version of this board that doesn't have B08-04?

2. Do you think this missing ROM could account for ALL of the problems I'm seeing? Or is there likely more to it?

3. What kind of EPROM/EEPROM/whatever else should I buy to make this chip myself from the MAME ROM (is there a guide for this anywhere?)

4. Is 3 a good idea or will it be easier / cheaper to just buy it from somewhere (where?)

 

Many thanks in advance if someone is able to help :)

Edited by DragonsTrap
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Have you tried reseating the roms yet? That'd be the first thing i'd do.

 

Edit: looking at photos of the PCB online it seems certain you're completely missing the ROM you mention - here and here. I would ask for a refund, but if you're determined to keep the game, someone here should be able to tell you the EPROM equivalent and maybe even burn one for you (i'll happily do it, but i'm in NZ so postage will be a little more than locally).

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I took them all out, and put them all back in. They looked fine, I just gave them a quick wipe over.

I picked this up with a crappy-condition LAI-lowboy control panel (with spinner), and a working Tekken board all for $60 so.. even with the missing ROM it seems okay.

 

I think I'll have a hand at flashing an EPROM myself (I kind of wanted to get into that sort of thing anyway) - any advice?

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Yep all those issues could be caused by a missing ROM. The roms B08-XX roms are probably mask roms, you may well find that 1 or more of the ones you do have are bad. The B06 chips are PALs or GALs, it is only recently that these have been added to the ROM sets, and only the very popular games have got them so far, many games may never get them.

 

As mentioned, I would burn a new chip to go in the gap and then if you still have issues I would verify the rest. As they are probably mask roms you have to be careful when choosing replacement EPROMs to use in their place, the pinout of mask roms is often quite different to eproms of the same size, confirming where the 5V pin is essential.

 

Have you been fed bullshit by the selller? Possibly, the board would not work without that chip, it is slightly possible that it was loose and fell out, have found chips in the bottom of packing boxes before but its not that likely.

 

That board is decked out for either 512kbit or 1024kbit chips by the way, which is what the (512/1M) marking means, this is why every second socket is empty. Eproms cost a fortune when this board was new and the sweetspot pricewise was always changing, board makers hedged their bets by making boards like this that would accept either 8x512kbit chips or 4x1024kbit chips depending on what was cheaper, the price difference would have been hundreds of dollars per board at the time.

 

From the photo these are 28 pin chips and would be 1Meg capacity. EPROM pinouts got messy at the 1Meg mark and there are at least half a dozen different pinouts. Am fairly sure there isnt a 28 pin EPROM you can burn and drop in to replace these mask roms. You may have to build a small adaptor for a 32 pin chip.

Edited by Womble
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Thanks heaps for the info womble..

I figured the 512/1M meant that 512/1024 ROM chips could be used but I didn't know which it was.

The gapped placement means they're likely all 1024, but (price being a concern as you mention) would it be safe to assume

that the last ROM would also be 1024? EDIT: nevermind, I checked the MAME set, all the same size :)

 

..would any games use (or would the board even allow) a mixing of the two?

i.e. 1024, gap, 1024, gap, 512?

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EPROM pinouts got messy at the 1Meg mark and there are at least half a dozen different pinouts. Am fairly sure there isnt a 28 pin EPROM you can burn and drop in to replace these mask roms. You may have to build a small adaptor for a 32 pin chip.

If an adapter was made from 32 to 28.. do you know if this pinout would be correct?

28to32.gif

 

For the EPROMs, does it matter how the memory is broken down?

For example, this one http://www.digchip.com/datasheets/parts/datasheet/000/271024.php

is broken down as 1024 = 64K x 16

I can imagine that memory addresses may not quite work the same way, but there might be a layer of abstraction so that it may not matter?

 

Thanks.

Edited by DragonsTrap
Another question
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The MAME ROM sizes are 1/8th of the EPROM size because there are 8 bits in each byte and ROMs are 8-bit. It can get complicated but basically multiply the size in bytes by 8 then match it with the correct EPROM size.

So if a ROM dump in MAME is 32768 bytes then you should program that to a 27256 EPROM.

If the ROM is 524288 bytes then program it to a 27C040 EPROM (or if 40 pin 27C4096 or 27C4200)

etc etc etc

 

Check my tutorial on Rom Dumping for more info.....

http://guru.mameworld.info/tutorials/how_to_dump/index.html

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Thanks for the link :)

I was aware of the difference between a bit and a byte, but the table on your site doesn't cover the type of ROM that I have.

Which is: a 28 pin, 1024 kilobit (128 kilobyte) ROM.. (edit: I've just pretty much confirmed to myself that this doesn't exist as an EPROM, why not?!)

 

What do you do for ROMs like this? Use a 32 pin and make a convertor socket as suggested by womble?

..also, do you know if the organisation of the EPROM (how that 1024 is divided internally) matters or not?

Edited by DragonsTrap
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Just had a thought...

 

Seeing as a 1024 kilobit EPROM with 28 legs doesn't seem to exist.. would it be possible to split the BS08-04 image into two halves and have it installed alongside the existing B08 ROMs, installed like this:

B08-01 (1024kb)

B08-02 (1024kb)

B08-03 (1024kb)

B08-04 [first half] (512kb)

B08-04 [second half] (512kb)

 

I guess this all depends on how memory addressing works and if it's possible to mix and match different memory types in a single configuration.

If it's NOT possible to mix and match.. then would this be possible if ALL B08-01 through to B08-04 were split in half and installed as 512 kilobit EPROMs?

 

Would be very interested to hear what people think of my idea and feedback regarding its feasibility.

Edited by DragonsTrap
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Thanks, I'll have a look around to see if there's a jumper anywhere.

 

So.. would replacing ALL the B08-XX (in the section that allows 512/1024) with 512 EPROMs work?

I.e.

B08-01 [1st half] (512kbit EPROM)

B08-01 [2nd half] (512kbit EPROM)

B08-02 [1st half] (512kbit EPROM)

B08-02 [2nd half] (512kbit EPROM)

B08-03 [1st half] (512kbit EPROM)

B08-03 [2nd half] (512kbit EPROM)

B08-04 [1st half] (512kbit EPROM)

B08-04 [2nd half] (512kbit EPROM)

?

 

If addressing is not a problem, it seems like it should, right?

 

Also, does the organisation of the chip matter? All the component sellers seem to mention this part,

how the memory is broken up internally into 'blocks/segments' (probably the wrong words).

Edited by DragonsTrap
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Theres more to EPROMs than simple addressing, the problem is that the /OE (output enable) pin needs to be driven correctly at the sockets. For the purposes of discussion think of a 1MB chip as containing two halves, each of 512kbits. If socket A has a 1Mbit chip in it then when the board is reading both the lower and upper 512kbit regions then the /OE at THAT socket has to be low as both halves live there. If socket A and socket B each have one half of what the 1Mbit chip contained then the /OE line on socket A has to be low when its half is being addressed, while socket B's /OE has to be high. When socket B is being read its /OE has to be low and socket A's has to be high. This is because the data bus is common to all the chips, only one must be allowed to talk at any given time or the chips talk over each other resulting in gibberish on the bus. Thre is probably a jumper that disables the logic that controls the 512kb /OE system, possibly just a wire link and not a jumper you can move yourself, it might be identifiable by the silkscreen markings, or it might not.

 

Dont worry about the block layout, for 8 bit systems you dont really have to worry about it. What you do have to worry about is whether those sockets on the board are the right pinout for 27c512 eproms or not. It is possible that the board was designed for 512kbit or 1024 mask roms, and to preserve pinout compatibility with the 1024bit masks they may have used the same pinout for the 512kbit mask roms. Bear in mind that the difference between a 512kbit chip and a 1024kbit chip on the address bus is a single extra address line on the larger chip.

 

It might help to explain what a mask rom actually is, apologies if you already know this, but it helps to know why things are this complicated. A mask rom is a rom that is not programmed, it is manufactured with the data already defined by its physical structure. The data is etched in from day 1 using a photo mask, such chips were common on boards for the graphics and sound data, ie data that was not likely to change throughout the life of the game. Many boards used EPROMs for their executable code as any bugs could be fixed, if they found a major bug in a batch of mask roms there was nothing they could do except bin the lot and etch new chips with the data structure fixed. The fact they dont need programming combined with the fact that you cant add just 1 leg to a chip as it has to have equal numbers of pins on both sides is why the chips are often non-standard pinout. To program an eprom you need to apply a programming voltage to the programming pin, if you dont need to program the chip then this is a pin you can get rid of. Getting rid of one pin doesnt help, you need to get rid of two pins to make a smaller chip, and one other pin that is rarely used is the /CS pin. Chip select is used to put the chip in a low power standby mode when it is logic high, waking the chip up from this state is too slow to be a useful way of controlling which chip can talk on the bus so in 99% of cases this pin is connected to ground and the /OE is used to determine which chip is selected to talk. So this can be connected internally and you shave 2 pins off the chip size. On early smaller eproms it was common to find a totally unused pin every 2 size increments, but as sizes ramped up everytime the capacity doubled they needed an extra address pin. To attempt to slow down the size blowout they started combining some functions together, on some chips the /OE pin is also the programming pin if it gets enough volts. Also as chip sizes grew the upper address pins got mixed up with other pins whose functions were set generations before so it ended up a mess. If you are going to build your own chip you can pretty much choose the pinout you want from day one and all you have to do is to wire up the board correctly, if you can save 2 pins per chip you can buy smaller sockets and have smaller boards, both cost savings. The problem comes when you want to use an eprom as a replacement as often there isnt actually a chip you can drop in.

 

In your case you need to confirm that the 5V and ground are where you expect them to be on a 27c512 chip, confirm that the pin you would suspect is /CS is tied to ground and then burn some 27c512 chips and see what happens, that is assuming you can find the link that switches between 27c512 and the 1Mb mask rom /OE control. With a scope or logic probe you could identify the address bus by pulling all the chips out and seeing which lines are active, but it wont tell you which line is which.

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Thanks womble for that incredibly informative post! I didn't know exactly what a mask ROM was (I'd never heard of it until you mentioned it earlier, and then I went off to wikipedia to find out ;) but your explanation definitely helped. I guess I better buy a multimeter some time soon (how I've survived so long without one is a worry) and an EPROM programmer. Thanks again :)
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Dont be tempted to spend much on a MM, when it comes to fixing boards all you will need really is the voltage function and the continuity function. Make sure the continuity feature has a beeper, the ultra cheap meters don't. Things like capacitance meter functions sound great, but its not actually the capacitance of capactitors that changes as they go bad, it is their ESR (equivalent series resistance) that goes up and that is not something you can measure with a MM anyway. So go cheap, go cheerful :)
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its probably a 28 pin 1M ROM. They are common. To replace it you need to use a NEC 27C1000 or whatever it was. I've done it several times in the past. I'm out of time now but I'll look into it later today.
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I think I found it, thanks.

 

(EDIT: all wrong, Ignore the following. I didn't know enough to check the chip specifications) TC531000 by Toshiba,uPD23C1000,uPD23C1010 by NEC

 

So, being mask ROMs, how would I write to them? Do I send my image to the chip manufacturer or what?

Really sucks that these don't seem to exist as EPROMs (anyone know why?)

Edited by DragonsTrap
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I said NEC 27C1000. Also 27C301G. Those are the ONLY chips you can use. They are 32 pin 1M EPROMs but are pin compatible with 28 pin 1M 231000 mask ROM. You can't program a mask ROM at all, so forget mask ROMs.

All you need to do is join a wire from pin 30 to pin 32 for VCC. The top 4 pins will just hang out of the socket, don't worry about them.

 


(1M) 128k x 8 mask rom (TC531000)     (1M) 128k x 8 EPROM (HN27C301)  
(23C1000)                                                 (NEC 27C1000) 
                                     Vpp    +-v-+ 32  Vcc            
                                     OE   2 |   | 31  PGM/           
A15  1 +-v-+ 28  VCC                  A15  3 |   | 30  nc             
A12  2 |   | 27  A14                  A12  4 |   | 29  A14            
A7   3 |   | 26  A13                  A7   5 |   | 28  A13            
A6   4 |   | 25  A8                   A6   6 |   | 27  A8             
A5   5 |   | 24  A9                   A5   7 |   | 26  A9             
A4   6 |   | 23  A11                  A4   8 |   | 25  A11            
A3   7 |   | 22  A16                  A3   9 |   | 24  A16            
A2   8 |   | 21  A10                  A2  10 |   | 23  A10            
A1   9 |   | 20  CE/                  A1  11 |   | 22  CE/            
A0  10 |   | 19  D7                   A0  12 |   | 21  D7             
D0  11 |   | 18  D6                   D0  13 |   | 20  D6             
D1  12 |   | 17  D5                   D1  14 |   | 19  D5             
D2  13 |   | 16  D4                   D2  15 |   | 18  D4             
GND 14 +---+ 15  D3                   GND 16 +---+ 17  D3             





Edited by TheGuru
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So, being mask ROMs, how would I write to them? Do I send my image to the chip manufacturer or what?

 

Yes you would have to send the image to them, and they would have a minimum order of at least 1000 units, possibly 10,000, not that anyone is making DIP mask ROMs anymore.

 

Really sucks that these don't seem to exist as EPROMs (anyone know why?)

 

Well I explained why mask ROMs exist, it was a way to make smaller chips with the same capacity as EPROM, so if you want that capacity in an EPROM you will find it has to have more pins.

 

As Guru says, get some 27c1000s and program them with the data, then link pin 32 to 30 and drop them into the socket with pins 1,2 and 31,32 hanging into free space and it will work.

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why mask ROMs exist, it was a way to make smaller chips with the same capacity as EPROM, so if you want that capacity in an EPROM you will find it has to have more pins.

Yeh, makes perfect sense once you bother to think about what each pin is actually doing (which I wasn't doing before).

 

Thanks heaps for that diagram. The other chips I saw would've required mpre pin re-wiring - this fix is surprisingly simple.

You're a life saver, will post results when I get it all up (which will be a while since I haven't got an EPROM programmer yet ;)

 

Thanks again womble

and thanks again guru! (your nick reminds me of Guru Meditation errors from my Amiga days)

Edited by DragonsTrap
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you're in WA? I can program an EPROM for you if so...

Thanks, that would be great! Yep, I'm in Perth. That'd save me from buying an EPROM programmer which, in all likelihood, I'll never use again (though I've been trying hard to convince myself that I'll get into ROM hacking to justify the purchase ;)).

 

Private message sent.

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TheGuru: I just had a look at your decapping project. It seems you're interested in decapping a different chip from Arkanoid 2; the B08-09 mask ROM?

Maybe I could donate mine to you - let you break it and dump the ROM image, then get you to flash it to an EPROM for me?

 

^if that's all possible; B08-09 is a 40pin chip, but I assume there must be some EPROM equivalent to it with 44 legs or something :)

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B08-09 is an Intel 8742 MCU (micro controller unit), usually used on boards as a security chip. If it was an basic eprom then its contents would have to be readable by the outside world therefore there would be no need to decap it. The MCU would have an internal ROM that is not externally readable but would contain the code running on the MCU internally, it is the behaviour of the MCU when running this internal code that provides the security functions of the chip.
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unless you can do without it for a year or two don't worry about it. it may also not come back at all or in multiple pieces. I prefer to buy the chips/sacrificial PCBs myself or have them donated with no strings attached.
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B08-09 is an Intel 8742 MCU (micro controller unit)...
Oh right, The B08-09 label for it threw me off. I just saw it on a list and didn't look into it further.

 

unless you can do without it for a year or two don't worry about it..
That wouldn't be the ideal situation :redface

 

Thanks.

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The site I went to is sold out of the NEC 27c512, but I checked the pinout schematic of an Intel chip

of the same number and it's identical so I might get that unless I go to another site.

EDIT: I know this is not the chip I need to replace the B08-04, I'm using this one for a High-score hack.

 

Any recommendations for site? (ordering from Perth)

 

One thing I'm not sure of though is which speed to get: 200ns, 150, 120.. ?

 

I'm going to list my assumptions, please someone let me know if I'm wrong:

- 200ns etc. is the amount of time taken to read something, so larger means slower

- it's okay to have a faster EPROM than the one I'm replacing but not slower

- a game this old (1987) would be using slow ROM so it wouldn't matter which I chose

 

Thanks

Edited by DragonsTrap
changed hi-score to high-score, that always annoys me in games ;)
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