Williams Defender
ROM Colour disambiguation

last updated October 20, 2014


There's lots of confusion over Defender rom boards and the rom colours.

I'll try to give you some idea of what its all about with the help of what i know from owning a LOT of defender pcbs and being involved in the dumping/verification of sets.

As a collector, having owned and sold maybe 10 Defender machines and selling maybe 40 pcb sets over the past 17 years, i knew of a white blue, green and red romset, but mame didn't reflect this. I had a rocky relationship with Mame in the beginning, a lot of devs were not interested in accuracy, just in getting new romsets into mame. When i made suggestions about correcting things, i was basically told, whatever was written in mame was sacred, and that i'd have to jump through a lot of hoops to provide evidence to support my case for the changes. Needless to say, that was time consuming and just not practical for me to prove what lot of collectors already knew. You could cobble a romset together from various sources and submit it, and it would be taken as gospel in Mame it seemed.

Thankfully things are different now, and now i spend a lot of my time trying to tidy up the problems Mame has inherited over a long history of ignoring basic naming conventions and submitting new drivers and mixed-romsets without any proof previously. These days at least, a photo is required to check the evidence for supporting naming conventions etc.. There are still a few common games that are not accurately dumped.. but we're getting there.


How can we accurately identify each rom?
Mame uses CRC's, in fact, so does a lot of test equipment, it is used to give a unique signature to a block of code. This signature means you dont have to compare byte-for-byte two large amounts of code side by side. If a CRC calculation sum performed on two blocks of code matches between them, you know they have to contain the same code.


Mame Rom questions and chronology:

- Until August 2008, Mame only showed 3 Defender romsets, called Red, Green and White.
- I owned a 'white' romset that was the only one i had ever seen. Others said they were 'uncommon but around' - to which i disagreed. I'd seen plenty of faded and shitty labels that looked white, but there was always a hint of a coloured stripe on there.
- I knew that the 'white' romset in Mame was actually just a mis-described 'Blue' romset from experience working on pcbs and code dumps i had made.
- I dumped my White romset, and found that rom10 would not read consistently, everything else was fine. Using the help of Chris Hardy, we deduced that my bad rom 10 could possibly be substituted by 'defcmnda.5' from 'defcmnd' because it sat in a contigious block of roms that were identical in CRC's. When tried it in mame, my white romset went from broken, to working, passing the power-on self-test now instead of resetting. We can only assume this substitution was correct using our best guess, see below:

- Using this rationale, we submitted it to mame, and it got added, with the old 'white' romset becoming the new 'blue' romset, see below :


- So, at this point, August 2008, there were 4 Defender romsets now in Mame, white, blue, green, red (from oldest to newest) called "defendw, defendb, defendb, defender"

- This obviously caused some confusion, beause people already had in their mame collections, but the CRC's or filenames now weren't matching up, so it seems everything got re-named and by mame 0.135 (oct 2009) the rom zip file names had changed to what we see today, which is defenderw, defenderb, defenderg, defender. I have not yet found the version of Mame where the names actually changed. [to-do]


links what date source
Mame 0.126 the last version of mame without the 'Blue' romset (its there but called white) 6 Jul 2008 Source code
mywhite.rar I dumped my white romset 8 Aug 2008 Me
Mame 0.127 The actual Defender White romset added - owned by Andy Welburn 19 Aug 2008 WHATSNEW.TXT

whats the age of the romsets? see in the table the serial number stickers and their groupings

Which romsets came first?
According to the Defender theory of operation manual for the EARLY pcbs(16P-3001-300 Oct 1981) page 30 :- Table 4-1 :
"Table 4-1 shows the two versions of Defender currently available"
Williams own naming: description Which Must mean romset
Defender "Version 1" - IC1,2,3 is shown to be using 4K roms BLUE
Defender "Version 2" - (IC1, 4) shown as 2K roms GREEN

It is interesting to note that in the Defender theory of operation manual for the LATER series of pcbs, (16P-3001-301 Oct 1981) page 29, the table 4-1 is repeated exactly as before, except the wording this time is:
"Table 4-1 shows the two versions of Defender produced"
Which contradicts reality. We know the Red set was the last produced as it supported the cocktail mode, is found on only later series pcbs, and had 2k roms at position 1 and 4. This statements seems to skip over the green set, or is just plain wrong. The manual is dated october 1981, Defender had been out for some time by this point, i just dont think Williams checked this over properly before printing...

By this logic, we know that the white romset must pre-date the green and red.



Rom labels!

- There's a few different types, but i have yet to see blue type 2
- I regularly see type 1/2 label styles mixed on the same pcb, seemingly from the factory, but this may or may not be true. Repairers over the years have not exactly been rigid when getting games to work again, and mixing would not be uncommon.

WHITE absolutely no sign of any pen marks
BLUE oversized, quite often found with top and bottom of the label missing
BLUE Mistaken for White in the past
GREEN look at it carefully, its definitely green, not blue.
GREEN Because of fading, this can look blue as well!
RED - semi-glossy appearance

- 1981 copyright date
- this label is very susceptible to fading away to nothing!
- "STD-A710" - code marked
- very common


There are no shared roms between red / green / white at all.
lower half of blue1 = green 1
upper half of blue1 = unique
green 1+4 = no match
RED code is unique, no matches with other sets
WHITE code is unique, no matches with other sets
green 3 is unique
green 4 is unique

difference between blue and green rom sets :



Rom set types:

Serials - approximate serial numbers the roms have been seen on. This does not mean someone in the past hasn't swapped the roms around from other pcbs, but it should give a general idea of which romsappeared when in the chronology...

I dont think i've seen a Red romset on an 'early' rom pcb, if you find that, it could be that you've had the roms transferred over from another pcb, i certainly know that happened among shelf-stored collectors pcbs and repairs.

colours Earliest Serials Seen comments
- 438642
These are the serial number range of Pilot/prototype machines - none have contained any unique romsets so far, all have been repaired/swapped/upgraded over the years
Blue 439159 (me) (yup! earlier than the white serial?!)
White 448815 (E.Thomas) the only pcb i've seen
Green 453011 (me)
454960 (me)

476807 (me)
492369 (me)
508562 (E.Thomas)
528383 (E.Thomas)


This page is in progress, please let me know what roms you have and what serial number your pcb is,
plus if you have high res images of your rom pcbs it would help!





Comments? Suggestions? Insults? Death threats? Go on, e-mail them to me.

These pages are (C) Andy Welburn 1996-2002. I cannot be held responsible if the information supplied herein results in a blown monitor/power supply/house fuse/mind. Oh yeah, have a nice day :)