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This article is Copyright 'The Guru' 2003-2009. The may not copy any portion of this for your own web site or printed publication.


This page briefly explains how to read ROMs (known as 'ROM dumping'), mostly for the purpose of emulation. The scope of this subject is EXTREMELY large in that it's impossible to cover every type of ROM and PCB combination here on this page. I've tried to be as thorough as possible and this info may be updated from time to time as I note more things that can be explained. However, this info should get you started. If you have further questions on this, feel free to contact me.

First of all, you need to get yourself some equipment. It's advisable for you to search the internet for "EPROM Programmer" and do some research yourself. There are literally hundreds of brands of EPROM programmers that will do the job, however I personally recommend the following models...

EETools  - TopMAX & TopMAX II (expensive, but powerful. Very very good software and EXCELLENT support with a forum)
Hilo Systems - All-11P3 or ALL-100 (again expensive, but powerful)
Andromeda Research Labs - The EPROM+ with the DIP40/42 modules (very nice price!)

You can buy any EPROM programmer that covers the majority of devices used on arcade PCB's. There is no limit on how much you can spend to buy one of these devices. You can buy one for $150, one for $400 or you can buy the latest and greatest whizbang DataIO Unisite for $35000. (Note: DO NOT buy the Unisite, it's an overly complex piece of junk with an archaic and non-free software updating method that locks you into old technology.... PS, anyone want to buy a cheap Data I/O Unisite ;-)
It just depends on how much you want to spend and your level of dedication. These can be bought from local Electronics shops, EBay, over the internet from many, many places or directly from the manufacturer or distributor. The key is research. Arcade PCB's use some of the most sophisticated technology on the market today, so do yourself a favor and look around first before you buy a lemon that can't dump your PCB.

I don't recommend you buy a PC-Based programmer. That is, one that has a card that plugs into the PC. These are usually cheaper and less capable or require an older PC, usually DOS-based. Those home-made jobs are usually unsatisfactory too, except for really simple tasks, so avoid those aswell.

Be sure to check that the programmer has at least a 42 pin ZIF (Zero Insertion Force) socket, otherwise you'll be cursing yourself for buying it when you find yourself needing to read some of the larger EPROMs that are found on arcade PCBs.

Also be sure to check that the programmer has the capability to read BIPOLAR PROMs (e.g. 82S123 / 82S129 etc). These are the tiny chips that usually hold color tables and such. If you don't dump those, the emulation will suffer due to the lack of the data held in these PROMs.

Just remember, the unit you buy must be able to do everything you want to do, otherwise it's a waste of money.... and as they say "You get what you pay for" so don't skimp on quality if you can avoid it ;-)

Visit the manufacturers' web site and look for a device listing of the supported devices. The basic supported devices should be at least....
2716, 2732, 2764, 27128, 27256, 27512, 27010, 27020, 27040, 27080, 27C1024, 27C2048, 27C4096, 574200, 578200, 27C160 and 27C322, plus BIPOLAR PROMs type 82S123 and 82S129. Of course, there are MANY equivalent types that I didn't list, but most are compatible with these I've listed above. If it has these devices supported, it's probably good enough for most of the PCB's that you will come across.

Some others you could consider are....

Dataman - S4 or 48XP models
Data IO - Plus 48
Labtool - 48XP
Leap Electronic - Leaper-48
Elnec - Labprog or Beeprog
Xeltec - Superpro 280U or Superpro 580U or Superpro 3000U
Logical Devices - Chipmaster 6000XP or Chipmaster5800U
BP Micro - BP-1400/240; probably quite expensive (UPDATE: In fact yes, it's US$5000), uses 100's of modules that replace the entire socket (and substantially lower your bank balance too!) and can drive up to 240 pins of every known type of chip on the market. A very powerful little gizmo!
Willem Programmer - A cheap kit based unit (~50 Euros) which is good enough for reading and programming EPROMs up to 4M (32 pins).
TOP 2048 (made in China?) - Seems to have good support, ZIF48 socket, English s/w and reasonable price too!

All of the Needhams EMP-1x/2x/3x units do not support ANY Bipolar PROMs, so DO NOT BUY ONE ;-)

If you're looking to buy some EPROMs or PROMs to program, there are plenty of places on the net. Just use Google and search 'buy EPROM'.
A few examples are.....
Jameco Electronics
Mouser Electronics
Digi-Key

If you have a programmer or supplier that you would like to recommend, please let me know and I'll add it to the list :-)

Ok, I could go on and on, but I'm not getting any commission from this, so these will do for now ;-)

So now you have a shiny new EPROM Programmer. What next? Well, get yourself a PCB. Here's a simple example....

Look closely at that pic. Looking for dumpable components is the key to success and will come with experience.
I'm sure you've spotted the EPROM....

Look even closer.....

As you can see, this one is clearly marked as MBM27128. That is the "type" and size of the EPROM. This one is 128k and the dump will be 128 / 8 = 16k, or 16384 bytes. For the purposes of this example, generally most EPROMs are 8 bit, so the size of the chip in K is usually divided by 8 to give it's capacity, though you don't need to be concerned with that :-)

You'll also note the large "F" and the "MBM". That is the manufacturers' symbol and code. This particular ROM is made by Fujitsu. You should try to learn the different types of EPROMs and manufacturers' symbols and EPROM codes so you can more easily recognise the correct type. If you read it as the wrong type, it's possible you can damage the contents which would be catastrophic on a rare PCB ;-)
Some common ones are....

Manufacturer Code Symbol
Actel (CPLD and FPGA)  
Altera (CPLD and FPGA)  
AMD AM
Atmel AT
Fujitsu MB or MBM
Hitachi HN
Intel D or i ,
Intersil (Bipolar PROMs)   , ,
Lattice (PALs/GALs)   , ,
Macronix MX
Mitsubishi M (or M5?)
Monolithic Memories (Biploar PROMs)  
National NM ,
Oki M ,
NEC uPD or D ,
Sharp LH
Signetics (now Philips, Bipolar PROMs)  
Sony CXK
Silicon Storage Technology  
ST Microelectronics ST ,
Texas Instruments TMS ,
Toshiba TC , ,

You can find a good cross-reference of EPROM and PROM types at The 'Wiretap' Arcade Game Collector's Archive, which were created by Al Kossow.

Update:
Sadly, it seems that archive is no longer online, so I've mirrored those cross-reference files here....
ROMref.txt - comparison list of EPROMs and equivalents.
PROMref.txt - comparison list of PROMs and equivalents.

Also, you can find a nice page with MANY manufacturers symbols here.

Now that we have located the victim, err... EPROM, we need to remove it. For the most part, ROMs are in sockets and are easily removed by inserting a small flat-bladed screwdriver or other similar tool under the side of the chip and gently levering it upwards, just slightly like this....
and a little bit more...

Here you can see I'm using a special tool that I made myself. Lever upwards VERY GENTLY. I can not stress this point enough. If you damage the EPROM or break off a leg, you'll be in some serious trouble which will require professional help to repair it.
Lever the other side gently upwards too, just slightly.....
and a little bit more...

Continue levering both sides _evenly_ until the EPROM is loose from it's socket and you can lift it out....
No more EPROM.... Magic!

Right, now that you have that EPROM in your hand, what do you do with it? Well, fire up your trusty EPROM programmer....

Next put the EPROM you just extracted into it's ZIF socket
and close the lever... noting the orientation of it.

Be sure to align the EPROM correctly. There is a notch or indentation near the top that marks pin 1. This pin should always be pointing towards the top of the ZIF socket, but the lowest pins always sit at the bottom of the socket. Check the pic if you're not sure what I mean. Also note that some EPROM programmers require the chip be sitting at the very top of the ZIF socket. Check the EPROM programmer and it's accompanying documentation to know for sure how the EPROM should be socketed. Be VERY VERY sure you get it right. If you put it in the wrong way, you will blow it up. There is no 2nd chance, it will blow up and you'll have a dead EPROM. Double... no triple check it, to be sure, to be sure, to be sure.

Next step is load the software that came with your EPROM programmer....

This will vary of course depending on your system and which software you have. Once loaded, you are greeted with the main program window....

Navigate your software to select the device. You should see a window containing many manufacturers and devices similar to this....

You need to select the correct type of chip. In our example we already know it's a Fujitsu chip, so select the manufacturer as Fujitsu first....
and then the type from the list in the right column... and click OK (or select it some way using the menu or whatever options your program has)

Now the main screen will say the current device is Fujitsu MBM27128....

Now we need to read it. This is done by selecting the "read" option in your software. Click that and after a few seconds, you'll see a checksum on the screen....

The EPROM programmer calculates this checksum automatically. It can be used for a check to know if you have a good read or not. If you get 0000h or ffffh or some other strange number, you may have a bad EPROM, it could be blank, or you selected the wrong device in the software.

A common mistake made by people is to rush. Never rush when reading EPROMs, you will only cause problems. Be sure to read the device at least 3 times. Yes that's right, 3 times. In between each read, remove the chip from the ZIF socket then put it back. Sounds dumb? One read is good enough you say.... not so my friend. The most common problem with reading EPROMs is dirt and corrosion on the pins that can cause a bad read. If you look at MAME, I'm sure you're aware of the number of bad reads that are present. If only the original dumper had read it 3 times to check the read was good... <sigh>

Before I move on, it's worthwhile to mention the other BIG problem with ROM dumping. The 2nd most common problem is reading ROMs using the wrong size. This often results in a read that is only half the size of the real chip. This most often happens when reading unmarked (black) MASKROMs. These chips are manufactured by many companies but generally, there are a few types that cover most MASKROMs. The key here is to be sure you select a type with the same pinout.

  • 32 pin chips equivalent to 27C010, 27C020, 27C040 and 27C080. These are 1Meg, 2Meg, 4Meg and 8Meg devices and are 8 bit. To be safe, if you don't know the size, read the chips as 27C040 or 27C080. A larger dump will just contain duplicate halves and can be chopped easily.
     
  • 40 pin chips equivalent to 27C1024, 27C2048, 27C4096. These are 1Meg, 2Meg and 4Meg devices and are 16 bit. If you don't know the size, read these types as 27C4096. You can also try to read them as the type listed directly below if you get a read where every second column contains 00's. To check the contents, use the "edit" option of your EPROM programmer software to view it after reading.
     
  • 40 pin chips equivalent to 574200. These are manufactured by Toshiba, are 4Meg devices and are 16 Bit also, but the pinout differs from the types above. These are commonly used to hold graphics or sound data.
     
  • 42 pin chips equivalent to 578200. These are 8Meg devices and are 16 bit. They are commonly used to hold graphics and sound data and are usually just black with little or no markings. There is another compatible type made by NEC (uPD27C8000) which is also equivalent to 578200. The pinout of these types is almost identical to the ones listed directly below only that there is one less address line (pin 42 has no connection, termed NC). If you know it's an 8M ROM, then read it as one, but if you're unsure, read it as a 27C160. It can be easily chopped in half afterwards if both halves are duplicated. This type is one of the most commonly misread types. Many bad dumps have 8M images in them that should actually be 16M!
     
  • 42 pin chips equivalent to 27C160 and 27C322. These EPROM equivalents are only manufactured by STS Microelectronics. This actual EPROM is not very common on arcade PCBs (though you will find them used a lot on late 90's and later Sega PCBs), but the MASKROM equivalent is extremely common and is used for holding graphics and sound data. The majority of bad dumps are of this size range. These chips are mostly just black, with little or no markings. To be safe, read the chips as 27C322 if you don't know the size. There is one simple way to test these chips. Check this sample 32M ROM pinout here...

    With reference to the above pic, you can see that pin 32 is labelled A20. This is the address line that enables the chip to access 32MBit of data. Pin 42, labelled A19, allows the chip to access 16MBits of data and pin 1 labelled A18, allows the chip to access 8MBits of data. You will never see a 42 pin ROM hold less than 8MBits. Using a multimeter set to continuity test (or diode test), check to see if pin 32 is joined to GND or +5V (either use the JAMMA connector, pins 1 and 3 or the power and ground pins of any logic chip on the PCB). If it has a direct connection to GND or +5V, then the chip is not 32MBit. If it goes somewhere else (i.e. not to GND or +5v) then the ROM is 32MBit. If pin 32 is joined to GND or +5v, check pin 42. If pin 42 is also joined to GND or +5v or has no connection at all to anything else, it's likely the ROM is 8M and you would read it as a 578200 (you can also read it as a 27C160 and just chop the resulting saved data in half). If pin 42 does not have a direct connection to GND or +5V, then the chip is 16MBit and you would read it as a 27C160 EPROM.
    See the summary table below for a clearer picture.... checking the pins in this order...
     
    How to check the size of 42 pin MASKROMs
    Step# If pin# is tied to... the ROM is... and you read it as...
    1 42 GND or +5V or NC 8M 578200 or 27C8000
    2 42 anything else (logic or another chip) goto step 3  
    3 32 GND or +5V or NC 16M 27C160
    4 32 anything else (logic or another chip) 32M 27C322

    You should be aware that PCBs can be wired to accept larger EPROMs but actaully use lower capacity ones on the board. So in that case, your checking might reveal that the PCB is set to accept 27C322 EPROMs, but the actual EPROMs on the PCB are 27C160 or 27C8000 etc. In this case, you read the chips as 27C322 and use ROMCMP to compare the ROM to see if it has duplicated halves (more on that below).

  • To further complicate matters, there are also 32M MASKROMs that have been programmed in BYTE mode which if read as a normal 27C322, will result in a bad read whereby all EVEN bytes are 00. These are commonly used by Konami for the sound data ROMs. To read these requires an extra read and then interleaving both reads together using some extra software. It's fairly time consuming to explain here, if you have this problem when reading 32M sound ROMs, contact me and I'll explain further :-)
     
  • Try to check the chip to determine it's real size. Reading it as the wrong type will result in a bad read. If you're still not sure, _visually_ inspect the tracks connected to the ROM to see where they go. The key pins are 32 and 42. For example, if you notice there are no tracks leading to pin 42, you know the ROM is not 32MBit (at least). Reference the table above to properly identify the ROM.
     
  • You can also purchase a real EPROM of the size you read the chip as and program it with your data, then test it on the PCB. If the game works with no faults, you can be fairly sure your read is ok. DO NOT EVER re-use the original ROM to test your read data. If it doesn't work, then you have lost the actual data. Don't skimp on quality just to avoid buying a few test EPROMs. Test EPROMs are very good and will save your ass one day, believe me ;-)
     
  • The MAME distribution contains a program that is SPECIFICALLY designed to test new reads. It's called ROMCMP and is able to find many types of errors in binary files such as duplicated halves, fixed bits (where every second byte is 0), stuck bits (where there is one (or more) pins that are not touching properly and was not active during the read, usually caused by dirt or a bent pin) and many other problems. For example, if you have absolutely no idea what size your 42 pin MASKROM is, read it as a 27C322. If ROMCMP complains about your data saying it has duplicate halves or duplicated quarters, then you know the ROM is less than 32MBit. If there are no messages from ROMCMP, generally the dump should be OK (assuming you didn't dump it half-size, which can't be checked for). It's better to read it at 2X the size and discover it's got duplicated halves, rather than read it at a lower size and find out after emulation begins that your MASKROM was dumped at half the real size and is bad! And it's even worse if you no longer have access to the PCB to re-read the chip! Argghh!!
    You can find ROMCMP in the regular MAME binary and source .zips at The Official MAMEDev Home Page. See the source for further info on using it to test your dumps.
     
  • It's not necessary to read ANY chip as it's specific manufactured type. Any equivalent type will do as long as the pinout matches (be VERY careful to ensure the pinout does match or you may damage the ROM!). You can find pinouts for most chips on the net if you search hard enough ;-)
    When reading MASKROMs, you MUST use an equivalent type since they're not programmable devices at all, they are manufactured with their contents at the factory. Which is why you don't find any EPROM programmer software containing MASKROM types and the reason for all the confusion about reading unknown MASKROMs which results in bad reads.

Ok, well getting back to the subject.....

So what can you do if you get a different read? Assuming you've selected the correct type of chip in your software, first thing is remove it from the EPROM programmers ZIF socket and clean the pins. You can do this by getting some very fine wet & dry sandpaper (around 600 grit, used by smash repair companies when spray-painting cars) and polishing the pins on both sides until it's shiny. Then put it back and re-read it, again, 3 times. If you still get different reads (this is where the checksum comes in, note the number on each read....), remove the EPROM again and carefully clean the insides of each leg too, that is, all the way around the leg, inside, outside and in-between each leg. It's time consuming I know, but you should eventually get a good read. If you still get bad reads, it's possible your EPROM is bad, or it is voltage sensitive and you need to increase or decrease the voltage by 0.1v to get a good read (you can check your software to see if it has this option, or ask someone who is more experienced with these matters to help you). Another trick is to heat up the ROM and read it while it's hot. Use a heatgun or similar to gently heat up the chip to about 60 degrees C (approx 140 degrees F). Use some tongs or pliers or tweezers to pick up the chip and put it into the ZIF socket and then read it. If that doesn't work, give up heating it. Do not think you can heat it more and achieve a result. You will only melt the chip, your EPROM programmer and your fingers and your house will burn down when your EPROM programmer catches fire.

Now that you have read the chip, you need to save it. Select the save option in your software....
Your software should have options to save the data as different types (Hex, Binary, ASCII etc), be sure to save it as RAW BINARY.

Type a filename to save it as, and click OK....
Make sure you name it properly. That is, use the labelling from the ROM for the name and the location as the extension. For our sample Fujitsu EPROM, the correct name would be 136059.5n. The location is generally found next to the chip (such as IC21, U33), or cross-referenced from the sides of the PCB which has numbers and letters on it (such as 5n, 21t etc).

That's it! You've dumped the EPROM and completed the task.

As I stated above, some arcade PCB's can use much more complex ways of storing their data. You may come across a PCB with many black MASKROMs that are unmarked and soldered into the PCB, similar to this...

If they are socketed, you can remove them and read them just like any other EPROM once you identify them. Take note that there could be MANY different types of ROMs on the PCB which can take you several hours to identify and read (and check!). Here's a nice example to show you just how complex it can get...
(This is a Sega Model 3 PCB)
Look carefully at this board. You'll notice some of the MASKROMs are a different shade of black. Don't be fooled into thinking they are a different size just because they look different. MASKROMs are manufactured by different companies and they can look different but still be the same! On the other hand, if they look different they could actually be different. So you'll need to do some research first to properly identify the chips.

If they are soldered into the PCB, you should seek professional help to extract them as you can easily damage the fine tracks on the PCB which will render your PCB non-working and will be extremely troublesome and expensive to repair.

There are other types such as surface mounted ROMs,
like this....   and this....    which are best left to professionals, since you need a whole pile of specialised and expensive equipment to read them. For soldered-in MASKROMs and surface mounted ROMs, I can dump them for you. I will do this for free (as long as the PCB is not already dumped), you only need to pay for postage both ways. If you have supported me in the past by loaning me PCB's etc, I will probably pay for return postage myself providing the item is small ;-)

Identifying the many types of EPROMs will come with experience. Just inspect the PCB for a while and you should be able to pick the EPROMs, MASKROMs and other components easily. You can email me for advise if required, just make sure you take some photos of your PCB so I can see the components clearly, or at least have some info about your PCB and EPROMs before you contact me.

If you have an EPROM image (a 'dump'), you may occasionally need to program it to a real EPROM. You can identify the EPROM size from the dumped file. Simply multiply the file size of the dump by 8. For example, if the dumped file size is 524288 bytes (i.e. 512k), the ROM type to fit that in would be a 27C040 (512k x 8 = 4M). The 2nd step is to look at your PCB and check the number of pins for the EPROM you are concerned about. This is important because in this case a 4M dump could also fit into a 27C4096 EPROM (4M 16 bit), but since that is a 40 pin ROM and in this example a 32 pin ROM is needed, 27C040 is the correct type. See the table below for reference.
 
# of ROM pins needed Image Size (dump)
in bytes
EPROM type
to use
24 pins 1024 (1k) 2708
2048 (2k) 2716
4096 (4k) 2732
28 pins 8192 (8k) 2764
16384 (16k) 27128
32768 (32k) 27256
65536 (64k) 27512
32 pins 131072 (1M) 27010
262144 (2M) 27020
524288 (4M) 27040
1048576 (8M) 27080
40 pins 131072 (1M) 271024
262144 (2M) 272048
524288 (4M) 274096
42 pins 1048576 (8M) 578200
2097152 (16M) 27C160
4194304 (32M) 27C322

Note! There are many, many equivalent types for the EPROMs listed in the table above.
Refer to the ROMref.txt ROM cross-reference file for more info.

Lastly, have fun.... this isn't a job :-)

This article is Copyright 'The Guru' 2003-2009. The may not copy any portion of this for your own web site or printed publication.


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