VOGONS


First post, by lemonlime

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Hi All,

I picked up a Number Nine Imagine 128 II card on eBay recently. The Cirrus Logic chip for basic VGA duties seems to work fine in DOS 6.22 and has a separate 512KB NEC 70ns chip the card. As soon as Windows loads the Imagine 128 II driver, I get artifacting with vertical stipes down the screen (see image). Resoultion/colour depth doesn't seem to matter. I get the same behavior in two different Windows 98 and Windows 2000 systems with the included Microsoft drivers. My initial thought is that one or more of the IBM 60ns EDO chips (there are 8 in total) used by the Imagine 128 II chip are bad.

Is anyone familiar with this card aware of anything that could cause the weird vertical bands that I'm seeing here? Or is my suspicion of bad DRAM likely the culprit here?

The chips are IBM IBM025161LG5D-60 parts, which seem to be very difficult to source these days. From what I can see, this stuff is 5V EDO 256Kx16, 60ns in a PDSO64 package. I can't find exact replacements but I can get a quantity of NEC ICs with similar specs at a reasonable price. They are NEC (UP)D482445GW-60 ICs. From what I can see, they are also 5V EDO 256Kx16 in PDSO64. Any thoughts on this? Also, any tips or suggestions on how to identify the bad ICs? or is the best bet just to replace them one at a time until the issue disappears?

The card:
img_6727.jpg

The IBM025161LG5D-60 memory used by the Imagine 128 II chip:
img_6728.jpg

The Cirrus Logic chip is used for basic non-accelerated VGA duties:
img_6410.jpg

What the vertical bands/artifacts look like:
img_6477-2.jpg

Thanks,
Mike

Reply 1 of 18, by weedeewee

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from the example photo you offer, I'd say that some datalines between the memory and imagine128 chip have a bad/failed contact, which could also be a bad chip...

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Reply 3 of 18, by lemonlime

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Thanks for your replies! The squeeze test was brilliant 😁

I narrowed the issue down to one corner of this DRAM chip here.

img_6729.jpg

If I put pressure on it, the artifacting changes and will sometimes disappear. I took a closer look with a microscope and poked a few of the legs at that corner. At least five of them have bad solder joints. I can freely move the legs side to side. Will need to do a reflow of that area and see if the issue is fixed.

bad-joints.jpg

Thanks again! Will report back on the results.

Reply 4 of 18, by Horun

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Wow ! Great work guys ! Hope you can fix it easily 😀

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor.

Reply 5 of 18, by Anonymous Coward

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Cl gd5424 doesn’t have a pci interface. How does this work?

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Reply 6 of 18, by Anonymous Coward

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Cl gd5424 doesn’t have a pci interface. How does this work?

"Will the highways on the internets become more few?" -Gee Dubya
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Reply 7 of 18, by darry

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Anonymous Coward wrote on 2022-07-06, 01:52:

Cl gd5424 doesn’t have a pci interface. How does this work?

My uneducated guess would be that the Imagine chip contains some kind of bridging logic that allows the Cirrus chip to work as if it was connected through an ISA (or VLB) to PCI bridge .

Reply 8 of 18, by lemonlime

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Success! There were actually seven pins on that memory chip with bad solder joints. I just reflowed them with a bit of fresh solder and the card now works perfectly.

I did a YouTube video on the repair for anyone interested in seeing it done under a microscope.

https://youtu.be/NDT8kTUil0k

Thanks again for the tips!

Reply 10 of 18, by pancakepuppy

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lemonlime wrote on 2022-07-08, 18:54:
Success! There were actually seven pins on that memory chip with bad solder joints. I just reflowed them with a bit of fresh sol […]
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Success! There were actually seven pins on that memory chip with bad solder joints. I just reflowed them with a bit of fresh solder and the card now works perfectly.

I did a YouTube video on the repair for anyone interested in seeing it done under a microscope.

https://youtu.be/NDT8kTUil0k

Thanks again for the tips!

Good work! I've got one of the late 128 Series 2s without the Cirrus Logic chip so if the newer VBIOS isn't easy to find, I should be able to dump mine

Reply 11 of 18, by lemonlime

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pancakepuppy wrote on 2022-07-08, 21:27:

Good work! I've got one of the late 128 Series 2s without the Cirrus Logic chip so if the newer VBIOS isn't easy to find, I should be able to dump mine

I've been searching for the newer VBIOS without success. If you don't mind taking a dump of your card's BIOS when you get a chance it would be very much appreciated!

Thanks again.

Reply 12 of 18, by quicknick

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Great job and excellent video!
I'm also interested in the newer VBIOS, as it might offer a chance to put my #9 card to good use (it's a Mac-only card, so no Cirrus Logic chip onboard).

Reply 13 of 18, by pancakepuppy

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Alright, I popped the VBIOS out of my "legacy-free" Imagine 128 Series II and read it out with a universal programmer. Let me know if you try this out on an older card and how it goes! 😀

Edit: For reference, my card's VBIOS part is a National Semiconductor NM27C256V. I think, in this package, it's one-time programmable. If the older ones are also OTP parts you may need to get a new EE/EPROM to program.

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Reply 15 of 18, by lemonlime

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pancakepuppy wrote on 2022-07-21, 00:37:

Alright, I popped the VBIOS out of my "legacy-free" Imagine 128 Series II and read it out with a universal programmer. Let me know if you try this out on an older card and how it goes! 😀

Edit: For reference, my card's VBIOS part is a National Semiconductor NM27C256V. I think, in this package, it's one-time programmable. If the older ones are also OTP parts you may need to get a new EE/EPROM to program.

Thanks very much for doing that! Will see if I can find a programmable chip for it.

Reply 16 of 18, by quicknick

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I ordered some chips (AT27C512R and W27C512P) and I'll have to wait their arrival for further testing (512kbit because that's why my card originally uses, I'll just concatenate the file 2x).

Tried what I had at hand, closest I could find was a W49F002 so I had to concatenate the file 8 times in order to fill it 😁
I expected it not to work (and of course it didn't!) since the chip enable and output enable pins are 22 and 24 compared to 23/25 on the original chip.
Another chip I had available was a SST39VF512 - closer in size but more incompatible - above pins still shifted, and Low Voltage version. Arrrgh!!!

Reply 17 of 18, by quicknick

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W27C512P chips arrived today, but no luck in getting my card to work.
I don't know what the correct route is in this particular case (original chip is 512kbit, new BIOS is 256kbit) so I tried all 3 possible combinations (image concatenated to fill the entire chip, or using just the first and then the second half of the chip), all result in "no videocard" beep code 🙁

pancakepuppy wrote on 2022-07-21, 00:37:

Alright, I popped the VBIOS out of my "legacy-free" Imagine 128 Series II and read it out with a universal programmer...

Could you please share some photos of your board? I can't seem to find the variant without the CL chip on the net, and I want to compare it with mine.

Reply 18 of 18, by pancakepuppy

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Images attached

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