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PS/1 2011 ACU project

W

whaka

Experienced Member
Joined
Feb 26, 2021
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90
Location
France
Hi,

don't know if it's the best section to speak about personal project, but i found it to be the more suitable.
so, 2011 owners surerly know one thing : ACU option is probabely rare as unicorn :D

as i recently aquired a 2011, and speaking with the creator of the PS/1 ressource page (hottobar, if i'm not wrong)
he told me it would be nice to have an ACU solution... i agreed, and starting to think about it...

so, in short, here it is :





the idea is to put the riser in an external box, under, or next the machine. with cables going trhu the 5"1/4 hole.
the ACU card will provide extra 5V and even the -5V the 2011 don't provide.
first pcb's are on the way to validate if i've done right or not :D (and there's some reasons for things may not work as expected...)
so, is there some people interesed for having one if everything is right ? i don't talk pricing now, it's a bit early... but i can tell for sure it'll not be a blood sucker :D
 
I find it very interesting, I did something similar just to address the lack of sound on the thing , things also didn't work as I expected them to.
XTIDE etc. It will be interesting to see what you can get working in the thing.



ktTSoWT.jpg
 
interesting too... did you provide extra juice ?
because as you have probably seen, the 2011 only provide one 5V rail, the 2 others have to be provided by an extra DC-DC converter via the 36V line.
so, if cards need the extra power, they can't work reliably.

in my case, i'm more scared about noise issue due to the switching DC-DC converter...
i pay attention on grounding it with it's own way, but things can be more complicated with noise troubles :D
 
well, first try yesterday, and it's (of course) a fail :D

my fear was true, but not from what i believed first. i face serious noise troubles, but it's all various noise comming from the system bus.
i saw it with the led of the XT-CF with compact flash removed. led blink for mostly everything...
once you reach 4 squares screen it blink when you move mouse, when you type on keyboard, when graphics moves, and if hard drive is plugged, you see his activities on the XT-XF led too, well a nice melting pot of noises
so, i smell a coupling issue. now, i think i really need to buy an oscilloscope... i can't go further without seeing what happen on the isa lines.
 
I am getting 5V/12V/-12V from the 2011 direct, I have provided for -5V but not installed the regulator.

I could not get any XT IDE working apart from XTIDE v1.1.5 with full mode disabled. This was an issue I could replicate in PCem.
SCSI/Audio/Network no issues though.
Extra load is <200mA max,

Rm43FBc.jpg

Picture of OPTI Soundcard

CRDezhG.jpg

This was taken when I had a different sound card installed.
 
nice, so your design at least work.
maybe i'm getting noise via the DC-DC converter...
for the moment, it can't even boot with a 16 bit card plugged in. i got error code 102.
i'm gonna try with only 5V provided by the 2011 and see what happen.
and maybe using 60cm cable is problematic too.

i'm waiting for my oscilloscope :D
 
well, in short : using only 5V from the PS/1 > not good too.
i received my oscilloscope, and the 5V i provide is clean on the acu card, and become garbage on the riser.
and mostly everything become garbage on the riser side... maybe a ground loop, crosstalk and too long cables, and so...

i reworked a bit on both card, added separated cable for power, as mixing power and small signals in the same cable is maybe not a good idea :D
reworked routing from 50 pin connectors to isa slot, as i used only one face of the pcb to route them, so very small space between traces (0.1mm... maybe possible crosstalk here, specially with CLK and OSC signals...). i alternate between front and back, this may help a bit.
and i grounded all together, trying to give a priviliegied way for the 5V i provide.
and btw, i removed the 5V comming from the PS/1, if i didn't connect them together before, they can meet via an expension card and... making a nice short...
then i'll try with 30cm cables, this may help too, specially with clock signals.

lot of things i don't really think about... learning pcb design is really fun :D
 
It is fun thats for sure.

I was a little concerned by your 5V only comment, so I rigged up a bare spare ISA board with voltmeters to see whats what.
And I am getting -12V, 12V and 5V out the ISA slot.

YqeK3KI.jpg
 
the real question is how many watt you can draw from this 5V line without burning motherboard traces. it's not documented, ibm don't say what's the purpose of this 5V rail.
they say the original ACU convert 36V into 5V, and also say 5V can provide 4.2A. but we don't know if they mixed the motherboard rail with the ACU 5V, or if he only serve to power, let's say the fan of the ACU for exmple.
but i guess for two little cards, the 2011 5V may be enough.
 
i forgot, that's my rework for now. this time i'll use 1,27mm pitch smd IDC header, this way i can separate each signal with one or more ground return in the cable.
and with the space i can get, i can put a stronger 7905 giving 500mA.



the harder is to find the 100 wires flat cable... for the moment, i can't find it with a decent price. from my regular suppliers, they only sell it in 30m reel, and it's really really exepensive.
 
Very nice

True you do have to be careful of power draw , I was just following the same riser design on 2 slot riser, like in DavejustDaves PS1

RbaCdkj.jpg
 
looks like things start to be good : https://www.youtube.com/watch?v=s1SwopbXGZA

Theoryboy : like you, i can't get the xt-cf v 4.1 to work.
i tried it without CF, rom screen never happen. but i get a ton of activity on the led... and for me, it's noise... ton of noise.
did you have the same thing with the ide version without any drive plugged on ?

because now, i don't understand why noise only affect this card and not others... make no sense to me.
i don't know if it's a flaw of the xt-cf himself, or an issue with it and this ps/1 in particular, or my design... i'm lost :D
 
it's the latest available from last month.
the bios need to be patched for using version 2 of the xtide rom.
for the moment, this can be considered as a kind of kludge, as you can't boot the original hdd without the xtide.
there's certainly a way for making a dedicated xtide rom for the ps/1, but it's far beyond my knowledge.
 
I am so happy to have found this project! Very exciting! How has progress been since July? I'm looking for an ACU for my 2011. Out of interest why have an ACU card to another riser instead of just all on one card? Or is that how IBM did it back in the day? Can you have a single ACU in the case with all cards? My main goal is to replace the hard drive which is failed with something like XT-CF.
 
hello

project didn't really go further for the moment, as i consider it mature enough now.
i made the choice of 2 cards because you need to find a solution if you want to easily enclose everything.
and this choice also give more slots than original acu.

the original acu provide 2 slots, and come with an enclosure wich make it look like the 2121.
i don't think it's easy for everyone to recreate such enclosure and make things look nice as original.

with the ribbon cable solution, you can use the external floppy "trapdoor" to pass cables through, then build a (i hope...) simplier enclosure.
or simply leaving things "naked" sitting next the central unit, but able to at least close it.

but depending your need, if you just need a xt-cf, maybe the theoryboy design is more interesting.
but i can't speak for him and don't know if he share/sell his project or not.
 
I'm very interested in buying a riser card for my 2011 if either of you have extra for sale. Your riser seems esp very clean to fit a soundcard with, TheoryBoy.
 
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