STe - Bad DMA Chip

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simbo

Re: STe - Bad DMA Chip

Postby simbo » Fri Jan 15, 2010 3:02 pm

jookie
the problem is OBVIOUSLY the buffer ic's
becouse the ack line doesnt go far enough down to close the gate on the buffer
it reaches from your pic about half as far to ground stretch the display to show low end transitions
and measure its time incrum
the slope isnt right for the ! ack levels
so its the dam buffers
it is a ! ack signal needed between 0.72 and 4.72 volts
on stfm i just measured the ack pin on the dma chip!!! it reaches on my scope .53 low and 5v high perfect
on ste with no corrected buffers i get at the port 0.74 low and 4.2 high {low end too high in value} not even right
but at the chip 0.68 and 4.75 {correct} but using the exact same ic i simply unplugged it from the ste
and moved it too the stfm why is there a .1v descrepancy in low and a .5v in high levels
becouse the ttl is getting in the way nothing more ffs....!
but using an 8 bit block transfer using 16 bit i get .72 low average and 4.13v average for a 16X16 block

they arent ack data at the right phase to then initiate a read/write cycle and this is the buffer ic's
as they introduce latency in needed read write phase and this makes a time displacment between !ack received at the dma
and the next read write phase allignment
early ste dma was in a socket
the stfm and early ste both use EXACTLY the same ic for DMA

made in the same place from the same ic's look on both machines good and bad at the die map
youll see its exactly the same

it saves face for atari just to increase the current to the ack line on the so called good dma chip
to then event a cycle of transfer than to ask users to change 4 ic's or two at a pinch

i think m8 you should change the buffers and report the results then
as well as before


i have three ste here
two didnt work with satan before i changed the buffer
one is the older dma and two the later one
so even the later chip will have issues
and this also shows bad in some hdd config's
if i place a hdd before the satan {i mean ultra satan} i cant see it on a good dma but the bad one see's it
replacing all logic as i said
all three machines work perfect as does satandisk and very well done !!! its a great tool

so... maybe someone else needs to check or jookie needs some act logic...??????

dont argue !! with 30 people change them then tell the other i think about 30 people so far have posted
we are all wrong please...? :mrgreen:

ive been bleating about it for i think 7 or more years so far

to replace a 'bad' dma you can just use one from an stfm maybe its bad also ???
its the same die just the buffers added and there timings not taken into account on some lines


this topic is a phew bar for sure !!!!!

adding a different psu may also help as a dc regulated and non regulated supply
will affect the link between the power ground and atari ground images....
and linkage.... in terms of millivolts this matters
with respect to the buffers needs .... and there own intensions


i know for a fact some ttl was bad very bad even reported on the news
especialy amerian makers becouse of there international policy change
this happened {workers werent happy}
this grew in the late 80's early 90's

and affects some ttl batches .... {some makers maybe bribed people also maybe intel who knows !!!}

simbo

Re: STe - Bad DMA Chip

Postby simbo » Fri Jan 15, 2010 3:33 pm

i will point out
that i have built several hundred dlls and i think about 80 models for TTL familys!!!
for many popular simulators as well as i think about 100 or more dll's for chips
and my own designs for vpots and slider controlled serial altered variable resistors in C++
and .mdf models for proteus vsm and my dlls are used by several makers of ic's including maxim and analog as well as
many private and company users and schools collages as far away from me as japan for group teaching

and i can assure you this is what you do ! BEFORE replacing a somewhat hard to find ic...

time simply put is 1/constant or an ordinal of time as per tick or 1 second

but voltage is 1/ 1tick /a constant voltage
and this is your bad slope you show jookie

just a bad climb to as close to 0v as the transistion allows
and its not fast enought for TTL 74LS types

you must have ACT types too work with satandisk 3.3v status gates
on ste megaste or the TT
BEFORE changing other dma type ic's
the ack line also uses one of the 74LS buffer chip's for coms with the port
so is also affected by not being able to close to below .2v

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Re: STe - Bad DMA Chip

Postby dma » Fri Jan 22, 2010 9:10 am

I was wondering something about some machines i got :
- a working STe but with bad DMA chip,
- a recently dead Mega-STe (that hurts big time, especialy as it stopped working for no reason and its PSU is fine :().

So i was wondering if the Mega-STe had a "C398739-001A" DMA chip somewhere on its board which i could extract and put on the STe, or not?
I couldn't locate any but i haven't taken everything appart yet, i guess i'm still hoping it could work again (foolish).

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Re: STe - Bad DMA Chip

Postby MRAtari » Fri Jan 22, 2010 12:20 pm

dma wrote:I was wondering something about some machines i got :
- a working STe but with bad DMA chip,
- a recently dead Mega-STe (that hurts big time, especialy as it stopped working for no reason and its PSU is fine :().

So i was wondering if the Mega-STe had a "C398739-001A" DMA chip somewhere on its board which i could extract and put on the STe, or not?
I couldn't locate any but i haven't taken everything appart yet, i guess i'm still hoping it could work again (foolish).


depends what year your mega STE was made, or maybe all mega STE's are like this i honestly don't know but from 1991 onwards ALL DMA chips changed shape in the STE/MEGA and were a small square SURFACE mounted chip marked C398739-001A

the only mega STE i ever had had this type

personally i'd leave your mega alone and try and repair it as that is far rarer than an STE.....

simbo

Re: STe - Bad DMA Chip

Postby simbo » Fri Jan 22, 2010 3:19 pm

dma wrote:I was wondering something about some machines i got :
- a working STe but with bad DMA chip,
- a recently dead Mega-STe (that hurts big time, especialy as it stopped working for no reason and its PSU is fine :().

So i was wondering if the Mega-STe had a "C398739-001A" DMA chip somewhere on its board which i could extract and put on the STe, or not?
I couldn't locate any but i haven't taken everything appart yet, i guess i'm still hoping it could work again (foolish).


i agree it would be easier to solve the mega issue
and far better it will be something simple ...im sure

why do people not just change the buffer ic's and be done with it
there is just no telling people anything

here is actual experiance by another member
read his topic

viewtopic.php?p=152530#p152530


this doc attached states two types of dma that are so called 'known faulty'
and its an extract of a tos upgrade doc
its funny both types are in older machines and run fine
the only differance is the buffers !!!
if you study the picture in the doc of the file system
youll see that data is being corrupted and not going missing
im sure lack of ack will cause corruption
so will there not being a decent low level state in the first place,,

as ive said its easier to issue one chip that ask users to change two or three or more that are mostly soldered..
You do not have the required permissions to view the files attached to this post.

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Re: STe - Bad DMA Chip

Postby dma » Tue Feb 02, 2010 1:52 pm

Of course i would indeed prefer 10 times to have the Mega-STe repaired... :roll:
But i had it tested by some electronic expert and he couldn't see where the problem was.
PSU is fine, the on/off led is powered when psu is switched on, but no display on screen and no disk activity.

Oh and thanks MrAtari, i got the same square shaped chip in the Mega-STe anyway.

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Re: STe - Bad DMA Chip

Postby Jookie » Thu Feb 04, 2010 10:19 pm

It took me few weeks to get the parts that Simbo recommended to use.
I removed the original chips and soldered sockets instead of them. I tried:
- 74LS06, 74LS74, 74LS244, 74LS245 - (as original) - 1st reset boot from US, 2nd boot - partition loss
- 74F06, 74ACT74, 74ACT44, 74ACT45 - (as Simbo recommended) - 1st reset boot from US, 2nd boot - partition loss
- 74F06, 74ACT74, 74F44, 74F45 - 1st reset boot from US, 2nd boot - partition loss (I didn't get 74F74, that's why I used the 74ACT74)
- I also tried the HC and HCT versions of all chips, the result was the same

As you can see, it didn't help me, as I expected (see here for more: http://joo.kie.sk/ultrasatan/steproblem/ ). So... is there anything else I can try before I change the DMA chip?

simbo

Re: STe - Bad DMA Chip

Postby simbo » Fri Feb 05, 2010 11:41 pm

Jookie wrote:It took me few weeks to get the parts that Simbo recommended to use.
I removed the original chips and soldered sockets instead of them. I tried:
- 74LS06, 74LS74, 74LS244, 74LS245 - (as original) - 1st reset boot from US, 2nd boot - partition loss
- 74F06, 74ACT74, 74ACT44, 74ACT45 - (as Simbo recommended) - 1st reset boot from US, 2nd boot - partition loss
- 74F06, 74ACT74, 74F44, 74F45 - 1st reset boot from US, 2nd boot - partition loss (I didn't get 74F74, that's why I used the 74ACT74)
- I also tried the HC and HCT versions of all chips, the result was the same

As you can see, it didn't help me, as I expected (see here for more: http://joo.kie.sk/ultrasatan/steproblem/ ). So... is there anything else I can try before I change the DMA chip?



hi jookie

i have an idea
as there seems to be a problem with reset always causing a partition loss
and we know from the past that an unprotected buffer from power up and down
causes this issue {like the bridge fix in the past} what it did was allow the right condition to exist in the bridge
that low pins would not allow further writes
{write state still enabled becouse of a missing flush data or a flag}

sound very familiar
you could look at the reset pulse period at boot up and the pulse period at reset
try holding the button in longer before resetting
and the bridge sources
somewhere here
r7 = r0 & r6; // r7 = ST is in RESET state
cc = r7 == 0; // if the ST is in reset state
r5 = 4 (Z); // brStat = E_RESET
if cc jump GetCmdByteEnd; // then jump out :)

you need also a catch exception to detect power down state
i used a buffer in the older bridge to do this
i take it its the usd your using ???

maybe adding an "is the atari powered down detect" ... to avoid overwrite
after reset
maybe another signal doesnt toggle on reset
or has the wrong period

another idea is to buffer the clock 8 input pin to the dma chip
and see if it corrects the issue
its been an issue in dma systems on other machine also
perhaps the clock inout circuit was redesigned when the new templates were made..

if i remember the mmu stops producing a clock8 when reset is pressed
and this could be why a full chip init isnt made on a reset
hence the differance between cold start everything fine
and running reset must be clock incrums and loading of the reset pin
internal to the dma chip's sections

so the logical choice is to use an inverter buffer first
then an open collector non inverting type if this doesnt cure it

much like the falcon

simbo

Re: STe - Bad DMA Chip

Postby simbo » Sat Feb 06, 2010 12:21 am

dma wrote:I was wondering something about some machines i got :
- a working STe but with bad DMA chip,
- a recently dead Mega-STe (that hurts big time, especialy as it stopped working for no reason and its PSU is fine :().

So i was wondering if the Mega-STe had a "C398739-001A" DMA chip somewhere on its board which i could extract and put on the STe, or not?
I couldn't locate any but i haven't taken everything appart yet, i guess i'm still hoping it could work again (foolish).



if you want to sell the damaged mega i can make it a project ill give you a decent price
ill also send you a good dma chip if needed

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Re: STe - Bad DMA Chip

Postby Jookie » Sat Feb 06, 2010 3:59 pm

Simbo, I suppose that you didn't look at my page where I wrote about that problem and which I copy and paste here when I talk about it ( http://joo.kie.sk/ultrasatan/steproblem/ ). The problem is not because of some faulty state or state detection when the ST is in RESET, but because there is no data going out of ST in the DMA WRITE phase (data is OK in PIO WRITE, PIO READ, DMA READ) - the data lines are all zeros in the DMA WRITE phase:
Image

This can be measured even at the pins of DMA chip in STE (this means before the bus drivers). Why the partitions are lost when ST is reset after the 1st successful boot is that ICD Pro after loading it self does some reading of partition tables, and then does READ boot/root sector [sector #0] (everything is fine at that time), but then it does WRITE back that sector and thus it rewrites it with all zeros (I don't know why the ICD Pro does something like that - maybe it checks if it can write to that media). The situation might be a bit different with HDDRIVER, because if I remember correctly it does not do any WRITE to media during the boot, so the HDDRIVER and partitions will work until the 1st write to media by user or some application (and that will probably screw up FAT).

simbo

Re: STe - Bad DMA Chip

Postby simbo » Sat Feb 06, 2010 8:35 pm

all this shows is as your site

a not ack line going low that doesnt quite make it
so the chip wont respond to the next command

it show nothing
about a complex signal

no data for be it a week clock or not enough drive

and this is not good enough !!!

i think your test unit has a bad pin's connection
becouse its mounted in a socket and has an unbuffered clock
nothing more
i have 3 ste machine
1 has a 'bad' dma
however it has never given partition loss totaly after a reset of any kind
infact it performs the same way as normal dma chips even though it has a bad dma die
but i changed the buffers
i think jookie you have a bad ground or something
i know that atleast two dia numbers have been declared 'bad'
and you just post one!!! the same one everyone says
but i know 3 from stfm that show the same issue

but its a case of change after or dont if you 'can' find it
i agree you have a very bad die in you test machine
however changing the chip should be a last find it resort
and thats me
change all associated then change the chip
did you add a buffer to the clock 8mhz supply to the chip first
or do these tests?

i feel the whole point to this topic
boils down to if we change the main 40 pin hard to find chip
or is there a better solution?
that all no brivado?
if we find an easier solution fine do that first

using sockets with ttl chips that run above even 5mhz is a bad solution for sure



above all making a fpga 'fit in' of a good dma chip
and shifter in one chip for vga also
is a better use of time

im not here to argue im here to solve

thats all in my overview

simbo

Re: STe - Bad DMA Chip

Postby simbo » Sat Feb 06, 2010 8:48 pm

the main problem with your argument jookie and other ste makers of firmware
is they spend no time to see where the problem actualy is

you see ack signal for 0 data
and if zero data when some is needed queerie why

is never taken in your pathetic code ive had to correct in the past

its blunt and that simple

power down is the same as reset

unless of dodge chip or code even uwe made efforts to fix the di is his hddriver v7 and 8

whereby reset should = power down state as should be and is detected

if zero data {there is no such thing} wait for next command string
catch exception for sure state !!!
however pio and dma are two different beasts
so the question should be


why does dma malfunction in dma mode on a reset
where pio works fine in both
its simple

inefficient external device codeing

plainly put
add a work around or many machine will lack the 'fixed' dma chip
and go to the bin!!
as i say i think its clock and reset of all unitation within the di thats the problem
and a simple inverting clock 8 buffer may cure it maybe
together with within a reset vector
allowed by some gates

with respect to time

power on and reset condition anomily is the problem
nothing else

simbo

Re: STe - Bad DMA Chip

Postby simbo » Sat Feb 06, 2010 8:56 pm

im fully sure
a software / simple hardware when needed

solution
will keep ste and mega ste and some TT out the bin

land fill

gone!!!! :mrgreen:

simbo

Re: STe - Bad DMA Chip

Postby simbo » Sat Feb 06, 2010 9:10 pm

i might agree there is a mixed solution

and thats to supply a satandisk varient code flash

if you see it on first boot cool
even the unit as i know youll see
no plugged in cards
scsi id hoged

but pio and dma reset issues
are a matter for the drivers and unit feedback and what you do next in driver terms

or clock or reset vectors

boot is boot and reset is the same
all past resident drivers

as the ataris series resets warm

to the last sub issues
like drivers etc !! and firmware interaction

so loading the same program from cold and hot is the same
for drivers unless the driver issues a reload from pio
and this is the problem
uwe hddriver triies to overcome ...

ask him for his sources
maybe there is a solution bad dma guys will benifit from
and share there cash within
for people with an 'ste tt or mega ste ' with a bad chip id
can overcome

basicaly these people have just now
to turn there machine off and on
to avoid partition loss??? after a reset???? this is poo jookie
and never happened from the past dma issues with scsi
so there is more flags and catches too this issue for sure

is this what you intimating is a good idea ???
when code can fix this

ie boot satan disk from cold flash this firmware if maybe you have a 'bad' dma chip

i just dont understand why code cant fix it for good!!!

thats all!

you could try flushing mem then reset from driver
both cold and hard if you see a distinction

then reload the driver

as if new on reset

even a 'warm' reset unit can load or overload new cold drivers

even with a fix drivers then!!!!

its no excuse to change a chip

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Re: STe - Bad DMA Chip

Postby wongck » Sun Feb 07, 2010 1:46 am

simbo wrote:im fully sure
a software / simple hardware when needed

solution
will keep ste and mega ste and some TT out the bin

land fill

gone!!!! :mrgreen:


unfortunately alot already there....
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My Atari stuff for sale - click here for list

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Re: STe - Bad DMA Chip

Postby Jookie » Sun Feb 07, 2010 9:43 am

simbo wrote:why does dma malfunction in dma mode on a reset
where pio works fine in both
its simple

inefficient external device codeing


I disagree. When no data goes out in DMA WRITE mode out of the DMA chip (even before the bus drivers) the external device can't do anything with it, no matter what external device it is (if it's made by me or it is any other ACSI device). You can't make a work-around for that in external device. I measured some signals in STE which (for now) prove that the problem is not in external device, not in bus drivers, but in the DMA chip (or something related to DMA chip which makes the DMA chip faulty in this case). Please tell me what should I measure or what should I try to help me fix the 'faulty DMA chip', but please - keep your reply short (to avoid tl;dr) and use simple english (because english is is not my 1st language).

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Re: STe - Bad DMA Chip

Postby Chandler » Sun Feb 07, 2010 5:28 pm

so if it's NOT the DMA chip

why did Atari change it with a revised one? :?:

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Re: STe - Bad DMA Chip

Postby Frank B » Mon Feb 08, 2010 12:17 am

Chandler wrote:so if it's NOT the DMA chip

why did Atari change it with a revised one? :?:


Why did it only affect non Atari hd solutions? Unless Atari were being economical with the truth :)

Frank

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Re: STe - Bad DMA Chip

Postby Chandler » Mon Feb 08, 2010 11:36 am

[/quote]

Why did it only affect non Atari hd solutions? Unless Atari were being economical with the truth :)

Frank[/quote]

the NON Atari issue is a myth

i had an Atari SH 205 corrupted by a dodgy DMA machine

they (Atari) probably blamed third party hardware so no one could claim compensation for their damaged hardware, if they (Atari) had admitted ANY hard drive would be affected then people would have grounds to make claims

all speculation of coarse :wink:

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Re: STe - Bad DMA Chip

Postby 1024MAK » Sat Jul 17, 2010 5:12 pm

Sorry to bump an old topic, but I was thinking :idea:, if the so called "bad" DMA chip (C025913-38) in the early STE's is the very same as the DMA chip in the earlier STFM machines, then why do these not suffer any HDD /UltraSatan problems? :?
Second question, has anyone with a STE with a "bad" DMA chip tried transplanting it into a STFM and testing to see if it gives problems with HDD and an UltraSatan? If not, why not? :?:
If you look at the circuit diagrams (and I am presuming that they are correct), the STFM does not have any 74 series TTL buffer chips or protection resistors between the DMA chip and the 19 way D connector. It does use one gate of a 74LS04 inverter (U51) for the Data Request line (D connector pin 19) unlike the STE which uses one gate of a 7406 open collector (U305)(which can only "pull-down" it's outputs to 0V, that why there is a 1k Ohm resistor on the output connected to +5V to "pull-up" the output).

If anyone does any further tests with a 'scope, it would be helpful to know what state the hardware is in during this "fault" condition :) .
What signal is on the following points / connections:-
U302 [74LS245] pin 1 (direction - R/W),
U302 [74LS245] pin 19 [enable pin, selects device, when not selected all data pins (outputs) go "tri" state (high impedance, an open circuit like mode)],
U308 [74LS74] pin 2 [D (for "data") input, this is the "FDCS" chip select output from the DMA chip],
plus of course the Data Request input pin on the DMA chip and at least one of the data pins on the DMA chip.

I suspect that it is a timing or sequence problem with the logic in the original DMA chip that did not show up until the 74 series TTL buffers were added in the STE.
Now either there is more than one problem here, or the timing problem is marginal, but varies between hardware. That's why some people can "fix" the problem by replacing some or all of the 74 TTL logic chips U302, U305, U307 and U308 with more modern CMOS versions. Note however that the 74LS244 and 74LS245 are buffer line drivers and "should" have no problem driving any TTL or LS TTL devices.
If however the chip that is connected to them is modern CMOS 3.3V logic device, well that's a whole new story, as it depends on the switching point of the inputs of that device.

So why did Atari add the 74 series TTL buffers you ask? Well, to provide better drive and / or protect the DMA chip. Why else would they have also added protection resisters in each data and output line?
So Atari tried improving on the original circuit and shot themselves in the foot! :lol: No wonder they produced a replacement chip... :wink:

One last thought, if you have a STE with a so called "bad" DMA chip (C025913-38), and you don't mind taking a risk, you could always remove the 74 series TTL buffer chip U302 [74LS245] and use wire links to connect the data "inputs" to the data "outputs" and see what happens... :lol:
It's not so simple for U307 [74LS244] as one buffer is used for another function (look at the circuit diagram).
Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (nearly forgot the Psion's)

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Re: STe - Bad DMA Chip

Postby simbo » Fri Jul 23, 2010 3:53 pm

1024MAK wrote:Sorry to bump an old topic, but I was thinking :idea:, if the so called "bad" DMA chip (C025913-38) in the early STE's is the very same as the DMA chip in the earlier STFM machines, then why do these not suffer any HDD /UltraSatan problems? :?
Second question, has anyone with a STE with a "bad" DMA chip tried transplanting it into a STFM and testing to see if it gives problems with HDD and an UltraSatan? If not, why not? :?:
If you look at the circuit diagrams (and I am presuming that they are correct), the STFM does not have any 74 series TTL buffer chips or protection resistors between the DMA chip and the 19 way D connector. It does use one gate of a 74LS04 inverter (U51) for the Data Request line (D connector pin 19) unlike the STE which uses one gate of a 7406 open collector (U305)(which can only "pull-down" it's outputs to 0V, that why there is a 1k Ohm resistor on the output connected to +5V to "pull-up" the output).

If anyone does any further tests with a 'scope, it would be helpful to know what state the hardware is in during this "fault" condition :) .
What signal is on the following points / connections:-
U302 [74LS245] pin 1 (direction - R/W),
U302 [74LS245] pin 19 [enable pin, selects device, when not selected all data pins (outputs) go "tri" state (high impedance, an open circuit like mode)],
U308 [74LS74] pin 2 [D (for "data") input, this is the "FDCS" chip select output from the DMA chip],
plus of course the Data Request input pin on the DMA chip and at least one of the data pins on the DMA chip.

I suspect that it is a timing or sequence problem with the logic in the original DMA chip that did not show up until the 74 series TTL buffers were added in the STE.
Now either there is more than one problem here, or the timing problem is marginal, but varies between hardware. That's why some people can "fix" the problem by replacing some or all of the 74 TTL logic chips U302, U305, U307 and U308 with more modern CMOS versions. Note however that the 74LS244 and 74LS245 are buffer line drivers and "should" have no problem driving any TTL or LS TTL devices.
If however the chip that is connected to them is modern CMOS 3.3V logic device, well that's a whole new story, as it depends on the switching point of the inputs of that device.

So why did Atari add the 74 series TTL buffers you ask? Well, to provide better drive and / or protect the DMA chip. Why else would they have also added protection resisters in each data and output line?
So Atari tried improving on the original circuit and shot themselves in the foot! :lol: No wonder they produced a replacement chip... :wink:

One last thought, if you have a STE with a so called "bad" DMA chip (C025913-38), and you don't mind taking a risk, you could always remove the 74 series TTL buffer chip U302 [74LS245] and use wire links to connect the data "inputs" to the data "outputs" and see what happens... :lol:
It's not so simple for U307 [74LS244] as one buffer is used for another function (look at the circuit diagram).



at last someone from another approch

i do agree but feel its better to replace all older logic with low current better chips {faster slew}
i dont agree adding the chips looses data
it simply speeds up access and yet unupdated chips then present an issue ...
i think you see the problem ic's

i think adding the 'fixed' dma is needed if possible but they are harder too find each day
therefore a set of retro plug in risers with a small fpga etc ssoc package or other with a port
possible i2c or other as a netable array for programming firmware replacement ic's
i think this will be a very adopted method in the future

using most cad tools you can make a pcb then wire a socket to it and bingo a programmable chip in vhdl or fpga

a good thing this add's is

first and second dual ide ports
better graphics
more expandable blitter's <-- and a better set of mpu's <---
all possible with fpga addin to sockets chip risers 'hard simchip pcb's on sockets'

Solarricht
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Re: STe - Bad DMA Chip

Postby Solarricht » Thu Aug 11, 2011 8:18 pm

Hi, an old topic but still relevant. Found this thread searching for reasons why i keep loosing one or more partitions from my cards. Was thinking it was HDdriver bug, but changed my mind. ive been using 2 STe's with an Ultrasatan, and SCSI card reader/ icd adscsi+ interface.tryed both card readers with both STe's. Problems loosing partions with all combinations, both CF & SD cards. Both STe's have bad DMA chip. Anyone know of a source of good ones still? Did this issue get resolved once and for all, or is there raging differences in opinion still? Really need to get this sorted to get any serious music created (especially having invested in nice MIDI hardware). Feel like ive spent months trying to build a system thats fundamentally flawed from the start. Run out of dosh. Wish i had a Falcon! Respect to everyone whos put time into this.

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TheRogue
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Re: STe - Bad DMA Chip

Postby TheRogue » Mon Jun 11, 2012 8:30 am

I hate to bring a thread back from the dead, but I have something to contribute to this. I have an STe that suddenly decided not to work with DMA hard disks anymore. It had ONLY EVER been used with an ATARI MegaFile30. I have made all the changes simbo recommends without accomplishing anything. I then changed the DMA chip and had everything work perfectly. I would like to point out that this STe worked flawlessly with the MegaFile30 for years before deciding not to work anymore. I have poked around with a logic analyzer and found exactly what Jookie's site led me to believe I would find. I think that these older DMA chips have some sort of fault in manufacturing that will cause them to suddenly crap out after possibly working well for a very long time. Perhaps some small amount of organic matter contaminate in the fab? I have heard of such things causing equally unusual symptoms in other ICs. The reason I wanted to make this post after this thread being dormant for so long is so that we can finally put simbo's way of thinking to bed. This is caused by a problem with the DMA IC, end of story. My personal experience has shown me this. Furthermore, I would point out that simbo's argument that he has an STe with a bad DMA chip that works with hard disks means nothing because mine worked flawlessly with a hard disk for years too. It really is something that causes random and sudden failure in the IC, again in my opinion probably some sort of contaminate in the fab.

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alexh
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Re: STe - Bad DMA Chip

Postby alexh » Mon Jun 11, 2012 1:21 pm

Unlikely to be anything to do with this subject which was about faulty designed chips from the factory. And very unlikely to be "contamination" (like zero percent chance!)

Chips can fail over time due to things such as electromigration. I would bet your failure was more likely due to something like that. Unlikely you had a bad designed chip which worked well for years and suddenly turned out to be one which was actually a bad one.

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TheRogue
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Re: STe - Bad DMA Chip

Postby TheRogue » Fri Jun 22, 2012 7:52 pm

The point I was trying to make was that just because simbo has a machine that has the faulty DMA chip (C025913-38) and can still use hard disks without issue does not mean that the problem lies somewhere besides the DMA chip because I have an STe with a C025913-38, and it worked with hard disks for a long time before suffering the exact symptoms described on Jookie's site. Also, I was just putting forward a theory about organic contaminates in the fab because I had a friend who worked for a company that manufactured ICs and he told me a story about chips coming from one particular plant failing either right from the factory or later on in very specific but unusual ways, and apparently they found out that some night shift janitor or other such person was heating up their food in the chip curing oven! Anyway, sorry if I didn't explain myself clearly the first time! :oops:


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