Faulty Ram / Faulty Oric

If you want to ask questions about how the machine works, peculiar details, the differences between models, here it is !
How to program the oric hardware (VIA, FDC, ...) is also welcome.
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Womble
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Faulty Ram / Faulty Oric

Post by Womble »

Hi All

I have just recieved all the way from the UK a mint condition Oric 1, cosmetically its mint but alas it doesnt work. I get rubbish on the RGB monitor and an angry buzzing noise from the Oric. I bought it knowing it was faulty thinking (based on the fault described by the seller) that reseating the ROM and the ULA chip would fix it (it solved a similar issue on the Atmos).

Nothing obviously wrong inside except that RAM chips 2 and 6 get very hot very quickly when power is applied. I have read that a hot ram chip can indicate it has failed.

My questions are these -

1) is the above behaviour normal for an oric with faulty ram?
2) Does the hot ram chip necessarily mean its a faulty chip?
3) How easy it is to find replacement chips of the correct type?
4) If I replace 2 should I replace them all?

I have ruled out the powersupply, the monitor and my RGB cabling as they all work perfectly with my also recently aquired Atmos.

Would love to get the 1 back on its feet, any advice would be most appreciated.

All the best

Womble.
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Womble
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Post by Womble »

Me again. A stint of reading around has pretty much answered my questions, I have cut the 2 ram chips off the board, unsoldered all the legs individually and soldered in 2 chip sockets. Have found a couple of places in Oz that sell the chips from between 1 and 10 quid each. Yeh 10 quid each - madness, wont be buying from them.

I still have one question tho - what would happen if I booted the machine with 2 ram chips missing? Would it just be short of 16KB and boot to basic or would it try to copy the rom into thin air and fail?
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Post by Dbug »

Well, the ROM is never copied to RAM for what I know, it is just "overlaying" the RAM.

Now, what would be the behaviour with missing RAM chips, I have absolutely no idea.

I guess you will have to wait for everybody to be back from end of year parties before you get any interesting answers !
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Womble
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Post by Womble »

Well I borrowed a couple of 4164 chips from my 48k speccy and the oric 1 now boots - progress!. Althought it reports an odd number of K free. I know speccy ram chips are usually half faulty anyway due to Sinclair using bad chips and then disabling the bad half in hardware. Yet it occured to me that my Atmos gives an odd number for ram free too - 39K.

What should an Oric report if all of its ram is good? I can only find 1 screenshot online and that shows 47k, which looks an odd number to me also.

This might explain why I can only get a single music demo to load on the atmos, all games just lock the machine. I also dont know if Zenon 1 and Hellion will actually run on an Oric 1.

Anybody know a good source for these 4164s, am beginning to think I will need to replace all the ram with sockets and new chips.
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Womble
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Post by Womble »

Found a good source for them, and that the 47K ish number is correct. Only outstanding question is ....

...as I am replacing 2 chips should I replace them all?

When taking into account of the postage for the chips its peanuts difference to buy 2 chips or 20.
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Womble
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Post by Womble »

Well the new ram chips are in - i replaced all 8 in the Oric 1 and .....


.... it doesnt work. On boot I now get a striped grid pattern on the screen and thats it. I admit I am stumped. Old ram out, sockets fitted and replacement set of chips swapped in. Why wouldnt this work.

The other problem is it seems that in a fully assembled Oric the ram chips are right up against the plastic of the base. With the sockets inbetween the PCB and the RAM the case no longer closes.

Update - had a brainwave - the oric PCB is dual sided - the original ram pin holes were through-plated. Its possible that the act of removing the old ram and resoldering has broken this very thin through-plating. So at the pin the circuit is divided into upper and lower traces. Surely if the 1st 2 8KB chips are connected correctly the machine would boot, it would have no free ram but should boot to the prompt. Will test the continuity between upper and lower when I get a chance.
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Twilighte
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Post by Twilighte »

Missing a couple of RAM chips would definately crash the machine, regardless which chips they were. The reason is simple. Unlike other 80's computers that had dynamic memory chips in groups of 8K and 16K the Oric has 8 chips where each one represents 65536 of a single bit.

However i remember one OUM meet when i'd brought in a broken Oric and Dave Wilkins looked at it, we noticed that one ram chip was bust but the machine amazingly booted!

Btw, Dave Wilkins method was always to place a good ram chip over the old like a piggy back. I'm not even sure he bothered to disconnect the broken one. :?
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Post by nobbysnuts »

Hi remembering my first early oric 1 it never booted up properly from new you had to plug power unit into wall then pull the power lead out and in on the back of the oric(making sure you dont stuff it into expansion port)then it booted .

wasn't there was a modification to fix this after early models?
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Womble
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Post by Womble »

Ah interesting - I have printed out the schematics so I can easily check that all the connections to the RAM are still intact. Makes a lot more sense on paper than it does by looking at the board itself.

Another odd point tho is with my Atmos. When I got it, it was showing 37K free when it booted. Surely it should be 48K ish - its missing 10KB. As I was ordering 8 chips for the O1 I ordered another 8 for the Atmos plus a couple of spares. Now I have installed 8 new chips it boots but still says it has 37K free.

What on earth would cause that? Its missing 10KB

Previously the Oric 1 had 2 dead chips (IC10 and IC13 )and once I replaced the IC10 chip the machine did boot, even tho IC13 was dead. From what I understand the lower 16KB of RAM is used to shadow the ROM so as long as the striped bits for the 1st 16KB are ok the machine will in fact boot. Only when you try to use the upper 48KB will you hit problems, neither machine would load anything other than small demos.

I dont think the Oric has anyway to know that the upper address space it sees is actually usable. Any thoughts?
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Post by nobbysnuts »

HI womble thought Id posted that oric 1s usually show 47k free but atmos's only show 37K. not sure why think its due to rom fix am I right anyone?
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Post by Womble »

Arse - thats unfortunate - so I performed major surgery on a healthy Atmos??? Couldnt find any info on the Atmos online - bought a book on the Oric 1 which had the screenshot showing the 47K, just assumed the Atmos was the same as the Oric 1 with all the bugs ironned out of the ROM.

Oric 1 is now back in the land of the living tho - found a suspect joint when buzzing through the ccts. Not 100% if it was at fault but when I 1st tested it it was open circuit and seconds later it was fine, may have disturbed it with the multimeter probes. Anyway - resoldered it and swapped in the known good RAM from the Atmos into the 1. It worked perfectly, swapped the ex Oric 1 RAM back into the Atmos and got the swirling garbage on the screen again, swapped out all the chips 1 by 1 until I found the a faulty one, replacing that stopped the swirling but left garbage. Went through the bank replacing all of the 7 remaining suspect ones and the 2nd one I swapped was the last dead one - good job I ordered 2 spare - now I have 2 working Orics and 2 spare chips that I know were DOA.

Question - are the games Hellion and Xenon Atmos compatible? Neither load on my Oric 1 or Atmos. The Atmos loads the p_drag music demo happily tho, (dont think thats Oric 1 compat) not sure I have good wav files for the games.
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Post by Dbug »

Arse - thats unfortunate - so I performed major surgery on a healthy Atmos??? Couldnt find any info on the Atmos online - bought a book on the Oric 1 which had the screenshot showing the 47K, just assumed the Atmos was the same as the Oric 1 with all the bugs ironned out of the ROM.
Arg, totaly missed the original message.
I could have told you that it's perfectly normal that an Oric Atmos displays 37631 bytes free... the difference is that the Atmos reserved 7 additional kilobytes for the case you want to use HIRES video mode. You can do GRAB (or is it RELEASE ?) to get this additional memory from BASIC.

On the Oric 1, switching to HIRES when a program is already running may result in overwritten variables...

For Xenon and Helion, there are Atmos compatible versions. Not sure they are Atmos only, or Atmos and Oric 1 compatible.
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