From: Mike Ranger Newsgroups: rec.games.video.arcade.collecting Subject: Tech: Williams Stupid RAM tricks Date: Tue, 08 Sep 1998 08:40:20 -0400 Organization: Dofasco Inc. Lines: 69 Message-ID: <35F525B4.4017@dofasco.ca> Reply-To: Mike_Ranger@dofasco.ca NNTP-Posting-Host: d17861.dofasco.ca Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.01 (WinNT; I) Hi all... Under the topic of "It worked for me" and a standard disclaimer...It worked for me. I take no responsibilty if you fry RAM by applying the wrong power to them. As many of you now know, I've spent the last 8 months immersed in the robotron/joust/stargate arcitecture, and to that end thought I would try the following hack. Clay has done some excellent work in giving us information that would allow us to use 4164's as replacements for 4116 RAM chips. The process for 24 of then, is, however tedious. I have used his hack for one or two chips and it has worked fine. Wouldn't it be nice if we could simply put in an unmodified 4164 set (all 24) into our CPU boards? Well we can. Here is how. All 4116 RAM must be removed. Populate the CPU board with all 4164 RAM's. Do not make any board modifiactions (Yeah!!!!). But for your power connections, here is what to do. Disconnect the -5 volts from pin 9 of the power connector. Leave pin 9 unconnected (see 4164 pinouts - pin 1 in NC). Disconnect the +12 V REG from pin 5 and supply it with +5 volts REG. Done. Notes: The board still requires +12 V unreg on pin 8, as it is used for the reset button circuit. You may build an adapter, for about 2 bucks, consisting of a male molex connector and a female molex connector, and putting it between your original power harness and the board. The board and it's harness is swappable in any machine. Populating woth 4164's and applying regular +12,-5 volts will fry the RAM. As well, populating any sockets with 4116 and using your modified harness will fry something! We owe this hack to the fact that Clay did the ground work, and Williams CPU boards only use the -5,+12 V Reg for the RAM. They are not used any where else on the board. Interesting to note, that if you look at the standar Williams linear supply drawings, we are no longer using 2/3 of the supply. We will still be using +5 volts for the CPU and ROM board,+12 V unreg for the CPU, and +/- 12 V unreg for the sound board (even though it says to run +5 to the sound, it is indeed not used). Since the +/- 12 v unreg is derived from the +5 V reg part of the supply, we are no longer using the -5V and the +12 V reg parts of the supply. I do not know, but seriously doubt if we are putting extra load on the +5 V Reg portion of the supply. I was using a switcher on my bench. Like I said, It worked for me. I ran the board for an hour, in demo mode and ram tests, with no problem. Well, almost no problems :-) In the process of swapping ram , I damaged a socket. You always run that risk, given the age of the sockets! In fact after the hour, the RAM was still cool to the touch. It may not be horribly usefull to you all, but hey, it was easy to try. I know of at least one other who was interested in the results, so I offered them up here. Mike -- ************************************************************* Mike Ranger, P. Eng Mike_Ranger@Dofasco.ca Senior Engineer Primary Automation Systems Dofasco Inc. Hamilton, Ont can The opinions expressed are Mine, not my company's. ************************************************************* Adios Senna