[Coco] Re : FREE Services For Members Of The CoCoList at Malted Media

[coco at yourdvd.net]

What 512k static ram are you using? the first to hit the scene were
semistatic requiring something like an 8ms? refresh or so (these were
hitachi). The current ones are fully static. The 4464 used in the 128k
machine use a bidirectional i/o line like the static rams. The 41256
has a seperate din and dout line but these are shorted together in the
coco 3 memory circuit. did you account for the 256k bank switch?

if all else fails you can make one of these:
ftp://ftp.maltedmedia.com/coco/TUTORIALS/How_To_Upgrade_To_512k_Without_A_Commercial_Memory_Board.zip



> -------- Original Message --------
> Subject: [Coco] Re : FREE Services For Members Of The CoCoList at
> Malted Media
> From: Sylvain Rousseau <surtoutnombliepas at yahoo.ca>
> Date: Fri, April 20, 2007 9:41 am
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> 
> I tried to made one myself (512k static ram for CoCo3) last winter but
> it don't works. I got an oscilloscope last week. I expect to
> investigate it soon. I hope it will works because I don't have a 512k
> CoCo3, only 128k so I can't try the new Sockmaster port of DonkeyKong
> :( I use a Lattice CPLD (isplsi1016e) to demux the Gime address bus.
> Sylvain ----- Message initial ---- De : "coco at yourdvd.net"  À :
> CoCoList for Color Computer Enthusiasts  Envoyé le : vendredi 20 avril
> 2007, 11 h 24 min 24 s Objet : Re: [Coco] FREE Services For Members Of
> The CoCoList at Malted Media You could actually modify the refresh (i
> think it has something to do with a cas before ras type refresh, but i
> can't remember) and make them work if you wanted to add some extra
> circuitry. I'll get into my box of simms and sort out all of the
> 256's. I was thinking about attempting to demultiplex the gime address
> bus so it could support 512k fully static rams (about 17 bucks each),
> but i haven't looked into it enough to see if it is a possibility. the
> gime is designed for dual 256k banks using a 256 cycle refresh. One
> bank is for even addresses, the other odd addresses. The banks are
> accessed by the two we signals. I though perhaps i could use cas and
> ras to latch the addresses and use the we signals to generate the
> upper address bit and make it work, but again, i haven't looked into
> it fully. -r > -------- Original Message -------- > Subject: Re:
> [Coco] FREE Services For Members Of The CoCoList at Malted > Media >
> From: Roger Merchberger  > Date: Fri, April 20, 2007 8:08 am > To:
> CoCoList for Color Computer Enthusiasts  > > Rumor has it that
> coco at yourdvd.net may have mentioned these words: > >i've got the 3 8
> and 9 chip versions. My question is, do i need to > >verify that they
> are 256k or if i send larger simms (they're all 30 > >pin), as long as
> they are 8/9 chip, will they work as 256k simms in > >your card? i can
> plug up and old 486 and verify them if i need to. I > >bought a lot of
> them because i thought i might need them one day. > >Bought all i
> could find regardless of mem size, but i want to make > sure >i send
> useable simms. -r Only the 8 or 9 chip 256K Simms (the > 9th chip is
> parity, which is ignored) will work on a CoCo - Mark > already
> educamated me on that fact in the past. It all has to do with > DRAM
> timing issues, and the 1Mbit chips just aren't refreshed the same > as
> the 256kbit chips. I have 80 1Meg 9-chip 30-pin Simms available > from
> an old DEC 3-processor 486 server, it rather sucks that I can't > use
> any of them for any of my CoCo (or other classic) equipment. I > wish
> I had enough knowledge to make 'em into a nice 80Meg Solid State >
> Drive ... IMHO that would be kewl beyond belief! Laterz, Roger "Merch"
> > Merchberger -- Roger "Merch" Merchberger | Anarchy doesn't scale
> well. > -- Me zmerch at 30below.com. | SysAdmin, Iceberg Computers --
> Coco > mailing list Coco at maltedmedia.com >
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