Hi Frank, How about we split the difference and settle on .73"? Try putting a 16-pin DIP (which should be .700" end to end) into a RAM module socket sideways and I think you'll find that it's a little too short; if you use .1" perfboard you'll have to bend the pins a bit.
In any case, the socket spacing is at least .100" wider than the RAM chip. As to using diodes, I've often used this technique but I must confess that I never measured the standby current. But I don't quite see why that should keep it out of the standby region; with a pull-up resistor and no selects pulling down the diodes /CE should be at Vcc. Also, at least one of the commercial modules used diodes, so perhaps it depends on the RAM chip; some experimentation might be in order. m ----- Original Message ----- From: "Francesco Messineo" <francesco.messi...@gmail.com> To: <m...@bitchin100.com> Sent: Thursday, March 15, 2018 1:27 PM Subject: Re: [M100] 8K RAM Chip On Thu, Mar 15, 2018 at 6:08 PM, Mike Stein <mhs.st...@gmail.com> wrote: > Yeah, there are a number of ways to deal with the non-standard RAM modules > in an M100; the pin spacing of the modules is .75 instead of the standard > .60, so you will probably have to make a little adapter board in any case. > spacing is actually 700 mils > A self-contained module has to combine the four discrete chip selects into > one, and also re-encode them into the binary upper two addresses. There are > various ways of doing that and I have some of the commercial circuits > somewhere but can't find them at the moment. > > One way would be a priority encoder as Fugu suggests. His 32K idea is clever > and you could just used diodes to combine the chip selects; as a matter of > fact you can also use an 8K chip and use diodes for the encoding instead of > the encoder IC. A word of warning about using diodes to combine the selects: all the low power cmos rams need close to Vdd or Vss levels on the select to have the lowest current consumption when in sleep mode (Vdd circa 3V inside the M100). If the ram chip doesn't go in the correct standby mode, the internal battery of the M100 is drained in about one day instead of the usual one month (tests done in my Olivetti M10 several times). Frank > > ----- Original Message ----- > From: Fugu ME100 > To: m...@bitchin100.com > Sent: Wednesday, March 14, 2018 5:14 PM > Subject: Re: [M100] 8K RAM Chip > > If you did not want to use the Libero method you could use a 74HC148 (or > similar) 8 to 3 line priority decoder and put the 4 CSx- lines into the > upper or lower 4 inputs of the ‘148. That would recreate 2 address lines and > a new CS- for the 8Kx8 SRAM. It could all mount on a proto-board and not > require any 'soldering to' the M100 :) I would guess the NEC board uses a > similar method but with an HC149 8-to-8 line priority encoder. > > Alternatively use a 32Kx8 SRAM and waste 3/4 of the space, but it would > still need the CSx- lines ANDed to generate the SRAM CS-. Again no soldering > on the M100 required. > > > > From: M100 <m100-boun...@lists.bitchin100.com> on behalf of Mike Stein > <mhs.st...@gmail.com> > Reply-To: <m...@bitchin100.com> > Date: Wednesday, March 14, 2018 at 12:19 PM > To: <m...@bitchin100.com> > Subject: Re: [M100] 8K RAM Chip > > It needs more than just remapping the signals; the required upper two > address lines are not available on the sockets so you either need to add > logic to recreate them or modify the main board. > > m > > ----- Original Message ----- > From: Gregory McGill > To: m...@bitchin100.com > Sent: Wednesday, March 14, 2018 1:22 PM > Subject: Re: [M100] 8K RAM Chip > > thanks! It seems like we should be able to use the 8x8 chip from the 102 > with some kludging of lines.. they are pretty close.. > > Greg > > On Wed, Mar 14, 2018 at 10:08 AM, Brian White <bw.al...@gmail.com> wrote: >> >> There are at least a few different "build your own ram upgrade" articles >> on club100 and other archives of old forum posts, and in magazines too I >> think but those are hard to search. >> >> Here's one that is not one of the old original ones I was thinking of, but >> looks ok. >> >> http://digilander.libero.it/rar2k/TRS80/Memory24k.html >> >> I have some NEC modules that work that I assume must have originally been >> meant for nec 8201a. They are a little pcb with a single ram chip and an >> additional chip probably a decoder of some sort to consume 4 chip-enable >> lines. I could take some photos of it and maybe it's circuit could be >> reverse engineered from that. >> >> https://photos.app.goo.gl/ZQle2id7AMWdX2bC3 >> >> Another option is QUAD, which is a thing that installs in the bus socket >> and displaces the internal ram with it's own full 32K, plus 3 more banks of >> 32K that you can switch between. Although you can't get a quad right now. >> Steven Adolph is testing his latest revision of the design and it's in >> between right now. He found problems with the old version and so removed it >> from oshpark, and th new version is not yet verified. >> >> But assuming that comes along sooner or later, that would upgrade you to >> 32K the same as if you had installed all 4 possible modules inside. >> >> -- >> bkw >> >> >> >> On Wed, Mar 14, 2018, 11:14 AM Gregory McGill <arcadeshop...@gmail.com> >> wrote: >>> >>> ok is there a source for the 100 chips? or a pcb? >>> >>> Greg >>> >>> On Wed, Mar 14, 2018 at 12:02 AM, Fugu ME100 <b4me...@hotmail.com> wrote: >>>> >>>> Just the 102, it uses a standard pin out. The 100 uses a special RAM >>>> module. >>>> >>>> From: M100 <m100-boun...@lists.bitchin100.com> on behalf of Gregory >>>> McGill <arcadeshop...@gmail.com> >>>> Reply-To: <m...@bitchin100.com> >>>> Date: Tuesday, March 13, 2018 at 10:58 PM >>>> To: <m...@bitchin100.com> >>>> Subject: Re: [M100] 8K RAM Chip >>>> >>>> oh wait these are 32x8 :) are these ones on ebay for the 100 or 102? or >>>> both? >>>> >>>> Greg >>>> >>>> On Fri, Mar 9, 2018 at 7:33 PM, Gregory McGill <arcadeshop...@gmail.com> >>>> wrote: >>>>> >>>>> if you have the pinouts I have a bunch of 8x8 srams around for TI99 >>>>> projects >>>>> >>>>> Greg >>>>> >>>>> On Fri, Mar 9, 2018 at 6:11 PM, Ken Pettit <petti...@gmail.com> wrote: >>>>>> >>>>>> Ahh, I see now the original email stated 102. So yeah, those will >>>>>> work. >>>>>> >>>>>> Ken >>>>>> >>>>>> >>>>>> On 3/9/18 6:09 PM, Fugu ME100 wrote: >>>>>>> >>>>>>> More if it was R/S :) >>>>>>> >>>>>>> This is the one >>>>>>> >>>>>>> https://www.ebay.com/itm/1-TOSHIBA-TC5565PL-15-64K-8Kx8-SRAM-CMOS-STATIC-RA >>>>>>> >>>>>>> M-5V-150NS-28-PIN-PDIP/321974484773?hash=item4af72cbf25:g:ldEAAOSwGotWlWd9 >>>>>>> you mean? >>>>>>> >>>>>>> >>>>>>> >>>>>>> On 9/3/18, 6:07 PM, "M100 on behalf of Peter Vollan" >>>>>>> <m100-boun...@lists.bitchin100.com on behalf of dprogra...@gmail.com> >>>>>>> wrote: >>>>>>> >>>>>>>> Wow, a quick check reveals a 8kX8 SRAM on ebay for $3. Didn't those >>>>>>>> "memory modules" cost about $30? >>>>>>>> >>>>>>>> >>>>>>>> On 9 March 2018 at 17:57, Chris Kmiec <ckmi...@gmail.com> wrote: >>>>>>>>> >>>>>>>>> Great, I'll go looking on the intrawebs :) >>>>>>>>> >>>>>>>>> You don't happen to have another REX, do you? :) >>>>>>>>> >>>>>>>>> Chris >>>>>>>>> >>>>>>>>> On Fri, Mar 9, 2018 at 7:01 PM, Fugu ME100 <b4me...@hotmail.com> >>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>> The chips are available they are standard 8Kx8 SRAM. Should be >>>>>>>>>> able to >>>>>>>>>> find some on line. >>>>>>>>>> >>>>>>>>>> Unfortunately the QUAD is only for the Model 100, it will not fit >>>>>>>>>> the >>>>>>>>>> 102. >>>>>>>>>> >>>>>>>>>> Congratulations on your new addition :) >>>>>>>>>> >>>>>>>>>> From: M100 <m100-boun...@lists.bitchin100.com> on behalf of Chris >>>>>>>>>> Kmiec >>>>>>>>>> <ckmi...@gmail.com> >>>>>>>>>> Reply-To: <m...@bitchin100.com> >>>>>>>>>> Date: Friday, March 9, 2018 at 4:33 PM >>>>>>>>>> To: <m...@bitchin100.com> >>>>>>>>>> Subject: [M100] 8K RAM Chip >>>>>>>>>> >>>>>>>>>> Are these available anywhere, or do I have to find a donor system? >>>>>>>>>> Just >>>>>>>>>> got a like-new 102, but no memory expansion. >>>>>>>>>> >>>>>>>>>> I'm assuming QUAD is no longer being made/sold? >>>>>>>>>> >>>>>>>>>> Thanks! >>>>>>>>> >>>>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >> >> On Mar 14, 2018 11:14 AM, "Gregory McGill" <arcadeshop...@gmail.com> >> wrote: >> >> ok is there a source for the 100 chips? or a pcb? >> >> Greg >> >> On Wed, Mar 14, 2018 at 12:02 AM, Fugu ME100 <b4me...@hotmail.com> wrote: >>> >>> Just the 102, it uses a standard pin out. The 100 uses a special RAM >>> module. >>> >>> From: M100 <m100-boun...@lists.bitchin100.com> on behalf of Gregory >>> McGill <arcadeshop...@gmail.com> >>> Reply-To: <m...@bitchin100.com> >>> Date: Tuesday, March 13, 2018 at 10:58 PM >>> To: <m...@bitchin100.com> >>> Subject: Re: [M100] 8K RAM Chip >>> >>> oh wait these are 32x8 :) are these ones on ebay for the 100 or 102? or >>> both? >>> >>> Greg >>> >>> On Fri, Mar 9, 2018 at 7:33 PM, Gregory McGill <arcadeshop...@gmail.com> >>> wrote: >>>> >>>> if you have the pinouts I have a bunch of 8x8 srams around for TI99 >>>> projects >>>> >>>> Greg >>>> >>>> On Fri, Mar 9, 2018 at 6:11 PM, Ken Pettit <petti...@gmail.com> wrote: >>>>> >>>>> Ahh, I see now the original email stated 102. So yeah, those will >>>>> work. >>>>> >>>>> Ken >>>>> >>>>> >>>>> On 3/9/18 6:09 PM, Fugu ME100 wrote: >>>>>> >>>>>> More if it was R/S :) >>>>>> >>>>>> This is the one >>>>>> >>>>>> https://www.ebay.com/itm/1-TOSHIBA-TC5565PL-15-64K-8Kx8-SRAM-CMOS-STATIC-RA >>>>>> >>>>>> M-5V-150NS-28-PIN-PDIP/321974484773?hash=item4af72cbf25:g:ldEAAOSwGotWlWd9 >>>>>> you mean? >>>>>> >>>>>> >>>>>> >>>>>> On 9/3/18, 6:07 PM, "M100 on behalf of Peter Vollan" >>>>>> <m100-boun...@lists.bitchin100.com on behalf of dprogra...@gmail.com> >>>>>> wrote: >>>>>> >>>>>>> Wow, a quick check reveals a 8kX8 SRAM on ebay for $3. Didn't those >>>>>>> "memory modules" cost about $30? >>>>>>> >>>>>>> >>>>>>> On 9 March 2018 at 17:57, Chris Kmiec <ckmi...@gmail.com> wrote: >>>>>>>> >>>>>>>> Great, I'll go looking on the intrawebs :) >>>>>>>> >>>>>>>> You don't happen to have another REX, do you? :) >>>>>>>> >>>>>>>> Chris >>>>>>>> >>>>>>>> On Fri, Mar 9, 2018 at 7:01 PM, Fugu ME100 <b4me...@hotmail.com> >>>>>>>> wrote: >>>>>>>>> >>>>>>>>> The chips are available they are standard 8Kx8 SRAM. Should be >>>>>>>>> able to >>>>>>>>> find some on line. >>>>>>>>> >>>>>>>>> Unfortunately the QUAD is only for the Model 100, it will not fit >>>>>>>>> the >>>>>>>>> 102. >>>>>>>>> >>>>>>>>> Congratulations on your new addition :) >>>>>>>>> >>>>>>>>> From: M100 <m100-boun...@lists.bitchin100.com> on behalf of Chris >>>>>>>>> Kmiec >>>>>>>>> <ckmi...@gmail.com> >>>>>>>>> Reply-To: <m...@bitchin100.com> >>>>>>>>> Date: Friday, March 9, 2018 at 4:33 PM >>>>>>>>> To: <m...@bitchin100.com> >>>>>>>>> Subject: [M100] 8K RAM Chip >>>>>>>>> >>>>>>>>> Are these available anywhere, or do I have to find a donor system? >>>>>>>>> Just >>>>>>>>> got a like-new 102, but no memory expansion. >>>>>>>>> >>>>>>>>> I'm assuming QUAD is no longer being made/sold? >>>>>>>>> >>>>>>>>> Thanks! >>>>>>>> >>>>>>>> >>>>>> >>>>> >>>> >>> >> >> >
