[Search for users] [Overall Top Noters] [List of all Conferences] [Download this site]

Conference 7.286::atarist

Title:	Atari ST, TT, & Falcon
Notice:	Please read note 1.0 and its replies before posting!
Moderator:	FUNYET::ANDERSON

Created:	Mon Apr 04 1988
Last Modified:	Tue May 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	1433
Total number of notes:	10312

907.0. "Memory causing hard disk (DMA) problems !!" by RDGE44::GOSSA () Fri Jun 22 1990 05:56

I posted the following message to comp.sys.atari.st, so far I havn't had
a great deal of response, can somebody help me here :-
 
	To answer some of my own questions : 
> 
>	I've just become the proud owner of a Third Coast 65meg (ST277N ?) hard
>disk. My question is should it be putting FM interference ?? I get wide band
>interference (I can hear the drive's stepper motor) at about 6ft form the 
>machine. A friend downstairs from me can pick up the drives noise output and 
>he's about 30ft and 2 walls away from the machine. (He has a portable radio so 
>the noise is not mains transmitted).
> 
>	Is my hard drive faulty ???
 
	Seems the culprit is not the hard disk but the memory expansion I put
in over the same weekend. It's fun (??) listening to the memory accesses when
using the computer (The little guy seems to go wild when opening a window). 
This still leaves me with the problem that my hard disk writes are unreliable.
 
>	Is there anything I can do to shield it ???
 
	I've Tried sheilding the memory expansion (which has to sit outside of
the shield due to size) this has a small effect, the <Sense $04>'s (Drive not
responding) become ALLMOST non-existant and <Write Fail $000n> become less 
frequent.
 
	The memory expansion is Xtra-Ram from Frontier Software, I've checked 
it for missing capacitors and resistors, but cannot find any. Does anyone
else have any experiences with this expansion board.
 
	I'm going to try toriod's on the power lines to try to filter the noise
out of the line. (If that's how it's transmitted).

>> The toriods had no effect if anything they made the problem worse - or
>> is it just that the problem has got worse on it's own ??
 
	Are there any problems with power losses from the MMU or DMA chips
when expanding memory. The computer is a 2 year olf 520STFM and the memory
board requires a plug into the top of the MMU and the removal of the Shifter
from its socket and insertion into a board which plugs into the shifter 
socket. Power is taken from one of these two connectors. The earth wire is 
attached to the earth wire input on the mains lead.
 
			- Andrew -

T.R	Title	User	Personal Name	Date	Lines
907.1		RUTILE::BISHOP		`Fri Jun 22 1990 09:11`	9
	Andrew, I haven't had any experience with theis, but i hope you sort it out! I have the same board sitting at home waiting for insertion! How easy was it to install? How long did it take you, and did you come up against any major problems? Lewis.
907.2	Mine works fine	COMICS::DSMMGR		`Fri Jun 22 1990 09:36`	18
	I have fitted a Frontier Xtra-RAM board in my 520STFM and it has not given me the slightest problem. The fitting took me about 1 1/2 - 2 hours all in and the hardest part was getting the Atari casing to close properly after seating the memory board where the instructions recommended it should sit. Eventually I got it to shut but it was a tight squeeze to say the very least !!!!!!!!!!!!!! The instructions were pretty clear and can be followed without any real technical knowhow. As I said, I have had no problems with the memory or my HD and have been entirely satisfied with the upgrade. I do hope that you get it worked out Andrew. Sorry if this reply has not been much practical help to you but I thought I'd throw in my tuppence worth. Cheers Jonathan
907.3	Check power, ground, and timing	PRNSYS::LOMICKAJ	Jeffrey A. Lomicka	`Fri Jun 22 1990 11:18`	20
	As far as the reliability problems go, there are two areas I would look at: 1. "grounding", not the earth, but the negative side of the power supply. This connection must be strong as iron - and done with a nice thick cable. The same holds true for power, to a lesser extent. Check the power local to the RAMs with an oscilliscope if you can, and compare the ground potential at the RAM to that right at the power supply. This could also contribute to the large ammount of FM radio interference you experience. Do they use a decoupling cap at each RAM? 2. "timing". What speed RAM did you use, and from what company? If I read your message correctly, it appears that the RAM works correctly when accessed by the 68000, but fails when accessed by the DMA controller. This could be caused by a slightly slower-than-average DMA controller trying to access slower-than-average RAMs. If you are using 150ns RAM, this may be your problem. This problem would be exacerbated by the length of the connecting wires for the address and data lines, and the quality of their connection to the main board. If you can narrow the problem down to a single bit, you may be able to just replace one RAM.
907.4		ASDS::POWERS	I Dream of Wires - G. Numan	`Fri Jun 22 1990 15:56`	12
	re .0 I am not much of an electronics person, but could it be the powersupply in the ST not having enough umph left to drive the DMA with your memory upgrade. I don't recall you mentioning how large your mem upgrade is, but if it's 4 meg and you didn't disable the original mem on board. Some systems have problems driving all this with the wimpy ST supply. Just a guess Bill Powers
907.5	is your MMU labeled with "IMP" ?	MGOI02::FALKENSTEIN	so many girls, so little time...	`Tue Jun 26 1990 03:54`	19
	The ST supports two memory banks, each with either 512kB or 2MB. With some of the STs this is not so easily possible. These are STs with a MMU from IMP. The two banks may only be filled with the same chips (both banks with 512kB or both banks with with 2MB). So if you want to upgrade a ST to 2MB, only bank 0 may have 2MB of memory chips and the internal RAM must be deselected completely. If you do not deselect the internal memory, the upgraded memory will not be accepted completely or you will have access errors. So with a IMP-MMU only 2MB or 4MB upgrades are possible, no mixed banks. To deselect the internal memory you have to put +5V to the RAS-line. Before the RAS-line which leads from MMU to the internal bank must be disconnected. With a upgrade to 4MB both internal banks have to be deselected. If the ground lines are to long or you got chips from different manufacturers or with different access times or you got a IMP-MMU and did not deselect the internal banks, this could cause your problems. Bernd
907.6	ST/2.5Mb Frontier A.O.K.	BAHTAT::LEWIS	Semper in excreta, solat varium est profundum	`Tue Jul 10 1990 09:54`	18
	I've used the Frontier (unpopulated board) with 100nS 1Mbit chips from a firm whose name escapes me but whose prices were quite attractive on an ST (not FM) with twin single sided drives and have used it for some time with no problems. 2.5 Mb is BRILL! LOADSA memory. I'm waiting for the delivery of a Third-Coast SCSI adapter and OMTI controller which had to be returned cos it was DOA, and maybe that will show something different. My board IS fitted internally without TOO much trouble but it was tight and I suspect that fitting it into an FM may be even tighter. Just a thought but have you tried the old standby of ensuring EVERYTHING fitted into sockets is a snug fit including all memory/ROM/CPU chips etc. I've had the odd occasion when all hell has broken loose with my machine and a 20 minute session re-seating all the bits has done wonders for it. Regards, Bob L.