[Coco] Grr!!! Bad MPI! No biscuit!

Tue May 8 14:23:21 EDT 2007

james,

In theory.

How many CC3's have you place a F245 in place of the LS245 and used a  
ribbon cable expansion out the cart port and viewed with various test  
equipment?

The CoCo was not designed for F parts and doesn't need them for the  
speed. The motherboard is of very low quality to today's standards.

I was kidding when I said count the number of times you used TTL. You  
did count them and listed.

If I said jump off a bridge I would hope you would NOT!!! PLEASE DON'T  
DO THAT!!!!! Ask anyone that knows me...I kid around  A LOT. :)

Regards,

Mark

Quoting jdaggett at gate.net:

> On 8 May 2007 at 8:30, Mark Marlette wrote:
>
>> james,
>>
>> Trying not to laugh....(count the # of times you used the term
>> TTL..... :)
>>
>> You are talking general about LS and common knowledge about logic
>> families. I was talking specifically about the LS245 and the CoCo.
>>
>> Mark
>> Cloud-9
>>
> *****************
>
> Yes the LS245 had to incorparate hysteresis so that it would have improved
> performance over the rest of the LSTTL family when driven by NMOS and CMOS
> devices. But the to make your blanket comment that because of the   
> hysteresis it
> is better than that of another family is not necessarily true. LSTTL  
>  family has
> poorer noise imunity than that of the TTL family and the F(ast)TTL   
> family.  That
> even includes the LS24* bus drivers.
>
> Yes there is
>
> TTL
> STTL
> LSTTL
> ALSTTL
> FTTL
>
> and probably a few more families of TTL variant logic.
>
> james
>
>
>>
>> Quoting jdaggett at gate.net:
>>
>> > On 7 May 2007 at 9:02, Mark Marlette wrote:
>> >
>> >> Robert,
>> >>
>> >> The LS245 has hystersis which helps in the noise arena. F245
>> >> doesn't.
>> >>
>> >> I wouldn't switch them.
>> >>
>> >> Regards,
>> >>
>> >> Mark
>> >>
>> > *************
>> >
>> >
>> > Noise immunity becomes a major issue only when you are mixing
>> > different classes of TTL logic. LIke LSTTL and STTL or LSTTL and
>> > FTTL. LSTTL to CMOS. When looking at low level state margins there
>> > is no difference between LSTTL and FTTL family for commercial grade.
>> > With High Level logic state FTTL has better noise immunity than
>> > LSTTL when you at greater extents from typical VCC voltages.
>> >
>> > Even with hysteresis, I would prefer FTTL over LSTTL for noise
>> > immunity. In fact I would take TTL over LSTTL. LSTTL inherently has
>> > noise issues. In order to reduce power draw that input circuitry to
>> > the gates have been   redesigned. What this does is improves power
>> > efficiencies at lower speed switching   and at steady state. FTTL is
>> > nothing more that a speed increase of the old standby
>> >  TTL logic. In
>> > order to gain speed advantages FTTL have higher steady state
>> > currents. They also have larger overall geometry for the transistors
>> > and thus more   current source and sink capabilities. FTTL have
>> > better power efficiency at higher   clock rates than do LSTTL.
>> >
>> > james
>> >
>> >> Quoting coco at yourdvd.net:
>> >>
>> >> > I believe Marty Goodman once recommended that the ls245 in the
>> >> > CoCo AND the MPI be replaced with a faster version (the ''F''
>> >> > version, I think he mentioned). -r
>> >> >
>> >> >> -------- Original Message --------
>> >> >> Subject: Re: [Coco] Grr!!!  Bad MPI!  No biscuit!
>> >> >> From: Gene Heskett <gene.heskett at verizon.net>
>> >> >> Date: Sat, May 05, 2007 1:48 pm
>> >> >> To: CoCoList for Color Computer Enthusiasts
>> >> >> <coco at maltedmedia.com>
>> >> >>
>> >> >> On Saturday 05 May 2007, Joel Ewy wrote:
>> >> >> >Gene Heskett wrote:
>> >> >> >> On Saturday 05 May 2007, Joel Ewy wrote:
>> >> >> >>> Jim Cox wrote:
>> >> >> >>>> I have a MPI board that someone gave me.  I am not sure if
>> >> >> >>>> it
>> >> >> works or
>> >> >> >>>> not, but it's yours.
>> >> >> >>>>
>> >> >> >>>> Jim
>> >> >> >>>> PS: We need a new MPI for the CoCo
>> >> >> >>>
>> >> >> >>> Here's a humble suggestion for anyone contemplating such a
>> >> >> >>> thing: Orient the board perpendicular to the desktop so that
>> >> >> >>> any cartridges plugged into it will be parallel with the
>> >> >> >>> desktop.  Having the disk controller stick up 8.5" from the
>> >> >> >>> surface of the desk is just a bit silly.
>> >> >> >>>
>> >> >> >>> As much as I loathe trying to find places to plug them all
>> >> >> >>> in,
>> >> >> maybe an
>> >> >> >>> external transformer would be a good idea here...
>> >> >> >>>
>> >> >> >>> Would it be feasible to put bi-directional bus drivers in a
>> >> >> >>> short cartridge and connect the CoCo to the MPI via a short
>> >> >> >>> length of
>> >> >> ribbon
>> >> >> >>> cable?  That would provide much greater flexibility in
>> >> >> >>> placement, and probably reduce the chances of bumping things
>> >> >> >>> out of place.
>> >> >> >>>
>> >> >> >>> JCE
>> >> >> >>
>> >> >> >> This idea falls over due to a bus contention in the mpi's
>> >> >> >> internal
>> >> >> timing,
>> >> >> >> which in turn causes a ground bounce that is only barely
>> >> >> >> tolerable
>> >> >> if the
>> >> >> >> grounding ear clips in the side port have a good clean grip
>> >> >> >> on the
>> >> >> mpi's
>> >> >> >> ground plane.  Additional jumpers of heavy wire to tie the
>> >> >> >> mpi's
>> >> >> rather
>> >> >> >> surpentine ground plane together also help, as does
>> >> >> >> additional
>> >> >> bypassing
>> >> >> >> near the ls245.  You can make it stable, as shipped, its a
>> >> >> >> house of
>> >> >> cards.
>> >> >> >
>> >> >> >Are you saying that this problem is intrinsic to any CoCo
>> >> >> >multi-pak design, or just Rad Shak's?  FWIW, I'm musing about a
>> >> >> >possible future product, not modifications to the existing
>> >> >> >design.
>> >> >>
>> >> >> I'd say it would be pretty well builtin, Joel, unless someone
>> >> >> actually went to the trouble of fixing the timing problems,
>> >> >> which are in actual fact quite narrow, existing for not more
>> >> >> than 10ns, but during that time its an absolute crowbar across
>> >> >> the ls245 in the mpi, and whatever is driving the buss on the
>> >> >> coco's side of the edge connector.  The ground bounce, measured
>> >> >> from the coco's ground plane, say at the contact ears, over to a
>> >> >> ground plane connection around the ls245 and its environs, can
>> >> >> exceed a volt for 8 to 10 ns in the shacks first version.  The
>> >> >> mods I made to mine pull it down to around 150mv, but its still
>> >> >> there.  They also lowered the operating temperature of that
>> >> >> ls245 by a noticeable with the back of your finger amount.
>> >> >>
>> >> >> I think, but won't swear, that its the turn around delay in the
>> >> >> ls245 itself, and that one of the faster chip families version
>> >> >> of it might alleviate it at least as well as the extra grounds
>> >> >> and bypassing I added to mine did.  I should have taken the time
>> >> >> to socket it and experiment but didn't. :(
>> >> >>
>> >> >> There needs to be a few ns of dead time, where the ls245 is
>> >> >> truly open in both directions on a switch in directions, but I'm
>> >> >> not sure how one would go about separating the read and write
>> >> >> functions in order to achieve a buss that's tri-stated on both
>> >> >> sides of it. That is whats needed to eliminate it though. I'd
>> >> >> guess that 5ns of dead time would be sufficient, based on what
>> >> >> my measly 100mhz dual trace scope says.  5ns is of course faster
>> >> >> than my scope, but it is useable to around 200 mhz as I've used
>> >> >> it to look at a channel 8 tv transmitter (175mhz), just not
>> >> >> anywhere near full height traces when stuff that fast goes by.
>> >> >> 10ns should cover it all, and that still leaves the coco with a
>> >> >> couple of eons to do stable reads and writes through it.
>> >> >>
>> >> >> >JCE
>> >> >> >
>> >> >> >>>> On Sat, 5 May 2007 03:12:01 -0600
>> >> >> >>>>
>> >> >> >>>>  Willard Goosey <goosey at virgo.sdc.org> wrote:
>> >> >> >>>>> My old-style MPI is apparently toast.  My CoCo has
>> >> >> >>>>> therefore lost access to its hard drive.  :-(
>> >> >> >>>>>
>> >> >> >>>>> I suspect power supply problems.  Either that or the
>> >> >> >>>>> upgrade PAL is loosing its mind.
>> >> >> >>>>>
>> >> >> >>>>> Just what I need, something else broken.
>> >> >> >>>>> Willard
>> >> >> >>>>> --
>> >> >> >>>>> Willard Goosey  goosey at sdc.org
>> >> >> >>>>> Socorro, New Mexico, USA
>> >> >> >>>>> "I've never been to Contempt!  Isn't that somewhere in New
>> >> >> >>>>> Mexico?"
>> >> >> >>>>>   --- Yacko
>> >> >> >>>>>
>> >> >> >>>>> --
>> >> >> >>>>> Coco mailing list
>> >> >> >>>>> Coco at maltedmedia.com
>> >> >> >>>>> http://five.pairlist.net/mailman/listinfo/coco
>> >> >> >>>>
>> >> >> >>>> --
>> >> >> >>>> Coco mailing list
>> >> >> >>>> Coco at maltedmedia.com
>> >> >> >>>> http://five.pairlist.net/mailman/listinfo/coco
>> >> >> >>>
>> >> >> >>> --
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>> >> >> >
>> >> >> >--
>> >> >> >Coco mailing list
>> >> >> >Coco at maltedmedia.com
>> >> >> >http://five.pairlist.net/mailman/listinfo/coco
>> >> >>
>> >> >>
>> >> >>
>> >> >> --
>> >> >> Cheers, Gene
>> >> >> "There are four boxes to be used in defense of liberty:
>> >> >>  soap, ballot, jury, and ammo. Please use in that order."
>> >> >> -Ed Howdershelt (Author)
>> >> >> Inara: "It wasn't entirely a disaster."
>> >> >>
>> >> >> Mal: "I got stabbed! Right here!"
>> >> >>
>> >> >> Inara: "You also lined up exciting new crime."
>> >> >> 				--Episode #4, "Shindig"
>> >> >>
>> >> >> --
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>> >> >
>> >> >
>> >> > --
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>> >> >
>> >>
>> >>
>> >>
>> >>
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>> >>
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>> >
>> >
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