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PEx ROM Project

dougg3

Well-known member
Regarding those bidirectional latches we were discussing earlier. The official name is "registered transceiver" and the part number is 74xxx543, where xxx is whatever logic family they're in. So, for example, SN74F543 for TI's plain 5V version. Or PI74FCT543 for Pericoms fast 5V version. They support eight bits at a time.

Cool! It seems like those might just be the ticket.

It seems similar to other 5V Flash ROMs like the SST39SF, and the datasheet for that chip says more about what happens if /OE and /WE are both asserted. "Write Inhibit Mode: Forcing OE# low, CE# high, or WE# high will inhibit the Write operation. This prevents inadvertent writes during power-up or power-down." Later it says that when /OE is asserted (regardless of the other control pins) the DQ pins will be High Z/ DOUT.

Good catch! I missed that in the SST39F040 datasheet. It kind of seems like the unlock sequence should basically already be providing enough protection anyway, but I guess it makes sense that they added that as well...just in case...
 

trag

Well-known member
I would interpret all this as meaning with /OE and /WE both asserted it definitely won't write anything, and you probably won't be able to read anything either.

Thank you, Steve. I felt like I had maybe read an exceptional case like that, but I couldn't find it again. But I wasn't willing to comb through the datasheet with a careful read again after I developed the question -- or rather, was distracted by other questions, like searching for registered transceivers....

Your conclusion makes sense. It still might be fun to test.
 

Trash80toHP_Mini

NIGHT STALKER
It would be worth checking the clearances available in various machines. Most of the ROM DIMMs are close enough to the CPU card, that they have several inches of height clearance.

That wouldn't be true though in the Beige G3, e.g. and certainly not in the PM6100.

It'll be a few off kinda deal for testing as I see it. My spacious Radius 81/110 case has but a small index fingertip thickness clearance between PSU and top edge of the DIMM. I'll bet Apple's cases are no better.

Your idea would also allow one to do away with the need for a DIMM style socket for every programmer.

Don't know what you mean there. I'm thinking a set of this type of adapter board pinned to a large carrier DIMM for experimentation:

SMT-2-DIP-00.JPG

Thinking a single set of ICs adapted to the board for starters?
 

Trash80toHP_Mini

NIGHT STALKER
Couldn't find a PSOP44 adapter, but SOIC32 adapter makes for a good example:

SOIC32-pic-00.JPG
Rough estimate puts a pair of them within DIMM's width and each module adapted to your reader/programmer? If not, a quartet of these saves you design time, PCB production cost and pin straightening jig for about $40?


edit: forgot to mention 44pin DIP sockets might be more convenient for installation/removal from carrier DIMM
than widely separated header socket strips . . .

. . . lower profile DIMM Carrier and no PSOP44 soldering involved! 🤪
 
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Trash80toHP_Mini

NIGHT STALKER
I've set up a test rig for PEx-in-a-Drawer on the short rack I had to move to the bedroom for post-flood Living/Dining Room carpet installation. I've identified the "bad" DigiPEx ROM DIMM and retested the 10 sec. "KILL ME!" crash of the other three. Gotta record that one, no lead-in music present. Gotta record the G3 memory test failure bomb if it won't hurt anything. "KILL ME! KILL ME!" bomb code on a customized DIMM for my Radius 81/110 or any other NuBus PPC machine would be most cool!

First run testing of the TriPEx ROM DIMM yields no crash sound after about 5 Minutes!

Fab news there! Haven't played with video cards yet. That'll come later as a carrot on the end of the stick whacking me unmercifully during the final phases of clearing said space for carpet install.
 

trag

Well-known member
@Trash80toHP_Mini Does the iconography mean that you got to the Flashing Question Mark with the TriPEx ROM?

How do I make this thing play brass wind flourishes?

[Later edit} Ah, I hovered over the final photo and got the title PEx-in-a-Drawer-n-TriPExROM-CuriousFloppy. I'd say that's conclusive enough.

Fantastic!! Thank you for testing even while dealing with drowned carpet.
 
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trag

Well-known member
@Trash80toHP_Mini BTW, if that worked, and only as time permits, be sure to test all four of the TriPEx ROMs. HAP might need one of them, it seems like. I'm still confused about exactly what he has, but it sounds like he has two systems and one ROM.

I think if James in UK and Hap get working ROMs for their systems and you have a working ROM for your system, then everyone we know of, with a PEx, has a working ROM.

Also, do you want to try the experiment of swapping the PLCC ROMs to the DigiBarn version and then trying the Digibarn ROM -- assuming there's any difference between them and what you already have? I can whip up a set, if needed/wanted.
 

mg.man

Well-known member
Hey folks... I don't have much to contribute here... other than an offer of transport from US to UK. I am currently visiting my folks in Ft. Collins, CO - for the first time since the outbreak. I'm due to head back to the UK on the 23rd, and so will be happy to expedite (and lower the cost) of Int'l shipping if any is required...
 

Trash80toHP_Mini

NIGHT STALKER
Curious Floppy has been achieved all right! Thanks much, trag!

Currently in the process of fabricating a 5.25" plexi drive cage for Pex-in-a-Drawer to keep the SCSI CD-ROM drive from flopping around a/o tipping over onto the board. Bootable TechTool 3.06 CD waiting in the wings!
 

Trash80toHP_Mini

NIGHT STALKER
Hey folks... I don't have much to contribute here... other than an offer of transport from US to UK. I am currently visiting my folks in Ft. Collins, CO - for the first time since the outbreak. I'm due to head back to the UK on the 23rd, and so will be happy to expedite (and lower the cost) of Int'l shipping if any is required...
That might be quite a contribution! Send trag a PM to see if he wants me to ship the DIMMSs to you for testing in England. I can post them directly to you in CO instead of to trag in TX.

Glad to hear you're seeing family again. Just had a family reunion for immediate relations and offspring last weekend. Id it was so good to see everyone who could come, many were still missed due to COVID, though everyone in the clan has been much blessed thru the outbreak(s) so far.
 

Trash80toHP_Mini

NIGHT STALKER
jtPEx (still-in-a Drawer) got a brand new plexi drive cage!

PEx-in-a-Drawer-Plexi-Drive-Cage-00.JPG

jtPEx-Boot-Sequence-00.JPG



jtPEx-Boot-Sequence-01.JPG

jtPEx-Boot-Sequence-02.JPG

jtPEx-Boot-Sequence-03.JPG

jtPEx-Boot-Sequence-04.JPG

jtPEx-Boot-Sequence-05.JPG

May not seem exciting to most all of you, but I've been waiting since the BigAssBoxLot™ to see something like this! 😁

Spent way too much time using that last screen, bughunting ADB squirreliness for far too long today. Now I understand the frustration of members who don't even have an ADB mouse. I've got a bunch of them but heaven knows where I stashed them. :rolleyes: Fave IIgs KBD's passthru seems flaky, DinoKids mouse (the only one I could find) still doesn't work correctly after boot, but the Kensington TrackBall is working quite nicely.
 
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trag

Well-known member
ADB squirreliness?

Does your board have a 341S0788 or 341S0060 CUDA on board? It'll be a little SOIC with I forget, somewhere between 16 and 24 pins, IIRC. I don't RC. It's actually 28 pins.


CUDA_341S0788.jpg

Later edit: Ah, I see you added some information. Squirrelyness is actually from devices, not controller. That's better.
 
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Trash80toHP_Mini

NIGHT STALKER
Indeed! I was excited when I saw the happy Mac booting from the TechTool CD, but that didn't go anywhere, fell off the edge of flatworld. 8.5 off the shelf installer purchased CD worked a treat. I was really excited when the off the shelf OS 9.0 installer went happy Mac, but that one walked the plank too. Oh well.

8.5 it is for now, gotta get started designing the loooong planned picture frame case for my suddenly working bare PEx board! Thank you my friend!
 
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Trash80toHP_Mini

NIGHT STALKER
This is wicked cool, nice job guys!
trag did a fabulous job! I just played with toys and I'm LOVING it! 😁

Pulled out a sealed-in-bag Savvio server drive for the occasion. I've got it and the cable for it sitting on top of the optical drive. What's the max. partition size for 8.5? I think this little SCA drive is 7.2GB maybe, dunno, been celebrating over a drink or three! 🤪

Now to find proper adapter, for those I know where to look, it's a question of whether I've bought one or not or yet!
 
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Trash80toHP_Mini

NIGHT STALKER
One last braggin' rights shot and it's off to bed. Peripherals problem solved . . .

Prototype-Heaven.JPG

. . . for the most part. Paladin KBD/TrackBall has no power Button, so I still need to daisy chain it off the ADB II, but damn, it's so nice to get rid of that monstrous Kensington Cue Ball for this DuoBall/KBD combo at a convenient working height. Spotting this prototype Keyboard/TrackBall was the reason I put in the $100 minimum bid to get the BigAssBoxLot™ a rolling. Love the thing, the PEx board was an unexpected dividend.

@haplain my keyboard is crumbling away on its own without having been an unforgivable shipping disaster.
 

jimjamyahauk

Well-known member
Amazing! This is so cool that it's working. Thanks so much to the skills of @trag in fabricating and making these.

I can't believe that over a decade since it was pointed out that the DigiBarn pex had a ROM DIMM, wrangling to borrow it from Bruce, and then some technical experimentation to get it working by updating the PLCC ROMs, and successful booting my ROM DIMM-less PEX that it has now been really possible to realise the next "dream" of getting the rest of the DIMM-less prototypes booting too!

Kudos to everyone's part in this, and especially @trag for actually having the knowledge, time and equipment for this.
 

jimjamyahauk

Well-known member
Hey folks... I don't have much to contribute here... other than an offer of transport from US to UK. I am currently visiting my folks in Ft. Collins, CO - for the first time since the outbreak. I'm due to head back to the UK on the 23rd, and so will be happy to expedite (and lower the cost) of Int'l shipping if any is required...
That would be very kind and an amazing contribution. Very happy for this to occur. Thank you so much... DM you my address. @mg.man
 
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