I found a lot of two 55nS AS6C6264 DIPs with free shipping from US for $16.61 on Ebay. Whether that would be a good deal depends on what Mouser or Digi-Key's shipping cost would be. Got some figuring to do!
On Mon, May 7, 2018 at 11:48 AM, Fugu ME100 <[email protected]> wrote: > If you have access to DigiKey then you can always buy parts there (or > Mouser). I used a 74HC148 as the decoder chip when I built my M100 RAM > module. There are quite a lot of ways to decode the 4 Chip Enables on the > RAM socket using a single IC. > > These are DIP parts. > > AS6C6264-55PCN RAM = 1450-1036-ND - $2.43 > 74HC148 Priority Decoder = 296-8233-5-ND - 43c > > If you want to try the 74HC86 = 296-8375-5-ND - 40c > > Cost ~$3, however S&H would be extra. > > > From: M100 <[email protected]> on behalf of Diggy Dude < > [email protected]> > Reply-To: <[email protected]> > Date: Monday, May 7, 2018 at 9:26 AM > To: <[email protected]> > Subject: Re: [M100] 8K RAM module > > Well, it looks like the only 7486s I have on hand are LS. What with buying > bulk parts I'll probably never use and waiting for the slow boat from > China, it'll probably be more cost-effective just to buy the module on > Arcade Shopper. Thanks for your help, guys! > > -- Jim > > On Mon, May 7, 2018 at 11:04 AM, Francesco Messineo < > [email protected]> wrote: > >> On Mon, May 7, 2018 at 4:42 PM, Diggy Dude <[email protected]> >> wrote: >> > To make sure I understand: >> > >> > Clean all pads and leads with flux.Will a flux pen suffice, or should >> liquid >> > flux be used? >> >> no, flux residue after soldering has to be removed. I use water-based >> flux, so I clean the boards with water and bake them to remove the >> water >> >> > >> > What specific 74HC and SRAM devices do you use? >> >> I use AS6C6264SCN memories, though they aren't guaranteed to have >> standby current lower than 4 uA, but I measure every module to be >> sure it meets this requirement. It's the only part that can be found >> new at this time. I have used batoches of several other SRAMs when >> I've found a good deal on ebay for example. >> I do all glue logic with a single 74HC86. >> >> > >> > On Mon, May 7, 2018 at 2:45 AM, Francesco Messineo >> > <[email protected]> wrote: >> >> >> >> On Mon, May 7, 2018 at 9:08 AM, Diggy Dude <[email protected] >> > >> >> wrote: >> >> > Thanks, Fugu! >> >> > >> >> > So the modern solution is a single SRAM and capacitor on a >> SOIC-to-DIP >> >> > breakout? What's the RAM chip they're using? >> >> >> >> and a logic chip (there're a few different approaches here) to combine >> >> the separate chip selects to a couple of addresses and a single select >> >> signal. My own version of the circuit uses the fewest ports possible >> >> (at least if nobody comes up with a different approach I couldn't >> >> think of). >> >> The RAM chip must be a CMOS static ram, 8kx8 and with low power >> >> standby (not all have this feature). The original 8k modules were >> >> specified for 4 uA max standby current, that allows the standby >> >> battery to keep the RAM content for over a month. Usually the suitable >> >> chips have L or LL in the part number, but you better check the >> >> datasheet for the fine details. Most of the suitable RAM chips have a >> >> measured standby current of 0.1 uA (often less) at 3.3V if the chip >> >> select are driven with the correct voltages. At these current levels, >> >> cleaning the soldering flux is a must. I've measured up to 15 uA of >> >> standby current on badly cleaned modules. YMMV. >> >> Glue logic *must* be 74HC family, it has a suitable current draw at >> >> 3.3V standby and suitable speed. In one case I've used 74AHC and it >> >> worked well too. >> >> >> >> > >> >> > -- Jim >> >> > >> >> > On Sun, May 6, 2018 at 10:29 PM, Fugu ME100 <[email protected]> >> wrote: >> >> >> >> >> >> You could try >> >> >> >> >> >> https://www.arcadeshopper.com/wp/?page_id=11#!/8k-RAM-module >> -for-Model-100/p/104430801/category=28313042 >> <https://nam03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.arcadeshopper.com%2Fwp%2F%3Fpage_id%3D11%23!%2F8k-RAM-module-for-Model-100%2Fp%2F104430801%2Fcategory%3D28313042&data=02%7C01%7C%7Cb8bb797123af403b53b708d5b43745b3%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636613071840276763&sdata=F4%2FPkPnXMzef8DB1N50baPzETrsjrbFiag0daGnMhzI%3D&reserved=0> >> >> >> >> >> >> They have the M100 modules if you want to buy. >> >> >> >> >> >> If you want to build your own there are PCBs on OSH Park for surface >> >> >> mount >> >> >> and DIP versions. >> >> >> >> >> >> No need for any pillaging :) >> >> >> >> >> >> From: M100 <[email protected]> on behalf of Diggy >> Dude >> >> >> <[email protected]> >> >> >> Reply-To: <[email protected]> >> >> >> Date: Sunday, May 6, 2018 at 8:13 PM >> >> >> To: <[email protected]> >> >> >> Subject: [M100] 8K RAM module >> >> >> >> >> >> Anyone know where I can get an additional 8K for my 24K M100 without >> >> >> pillaging another M100? Let's face it: if I got another M100, I'd be >> >> >> inclined to leave it intact. >> >> > >> >> > >> > >> > >> > >
