Fixing a Trident TVGA9000 card for an XT
For a long time now my dad has run his pools program, firstly on a TRS80, and for a number of years on an old IBM XT, this machine was built in the mid-80's and until recently still ran with an original IBM HDA monitor, and Seagate 10Mb HDD.
Until last year when the monitor went pop, we were left with a problem - find a HDA monitor (expensive and rare) or find an 8-bit ISA VGA card (less expensive, but quite rare).
Well, we found this Trident TVGA9000i model 7210 card on ebay:
Cost under £20 and auction shows it has jumpers to select 8-bit operation.
But we couldn't get any output on a VGA monitor when the computer was powered up.
I took the card and tried it in my Olivetti ETV500, but the same thing happened - no output, however my AMD K6-II system booted just fine with it installed.
Thinking it was a firmware issue we tried several different VGA Rom images, but all had the same result, the PC would just hang during boot. I put it aside to look at later.
I also found this webpage while looking for an 8-bit card: Sergey's isa-supervga card and while researching another project, I discovered there was an update last year. IBM XT's and accurate clones assert the ISA ALE signal at the wrong time, causing the VGA chip to crash. A fix was included, and I wondered if I could fix my card the same way.
The fix involves disconnecting the ALE line from the ISA bus and connecting it to 5V
This turned out to be reasonably easy, the pin travels a short way to a hole, then a short way on the front of the board before returning through another hole. I cut the trace just next to the pin, and cleaned the solder mask from the second hole so I could solder a fine wire into it. I've circled both points on this photo: (The wire is already attached)
I then found a capacitor connected to the 5V rail and ran the other end of the wire to it. On my card this is C11, and here is the final fix.
With a little trepidation I installed it in the Olivetti, and connected a VGA monitor, and powered it up. To my delight the VGA monitor fired up right away! I did need to change jumpers on the Olivetti to get it output to the VGA card but all seems to be working fine.
More tests will follow, but as I only have a basic MS-DOS 3.3 boot disk presently, these will probably wait until I can attach a hard drive, not easy as the Olivetti only has 8-Bit ISA slots, and short half height ones at that. Current plan is to build a XT-CF-Lite at some point.
Until last year when the monitor went pop, we were left with a problem - find a HDA monitor (expensive and rare) or find an 8-bit ISA VGA card (less expensive, but quite rare).
Well, we found this Trident TVGA9000i model 7210 card on ebay:
Cost under £20 and auction shows it has jumpers to select 8-bit operation.
But we couldn't get any output on a VGA monitor when the computer was powered up.
I took the card and tried it in my Olivetti ETV500, but the same thing happened - no output, however my AMD K6-II system booted just fine with it installed.
Thinking it was a firmware issue we tried several different VGA Rom images, but all had the same result, the PC would just hang during boot. I put it aside to look at later.
I also found this webpage while looking for an 8-bit card: Sergey's isa-supervga card and while researching another project, I discovered there was an update last year. IBM XT's and accurate clones assert the ISA ALE signal at the wrong time, causing the VGA chip to crash. A fix was included, and I wondered if I could fix my card the same way.
The fix involves disconnecting the ALE line from the ISA bus and connecting it to 5V
This turned out to be reasonably easy, the pin travels a short way to a hole, then a short way on the front of the board before returning through another hole. I cut the trace just next to the pin, and cleaned the solder mask from the second hole so I could solder a fine wire into it. I've circled both points on this photo: (The wire is already attached)
I then found a capacitor connected to the 5V rail and ran the other end of the wire to it. On my card this is C11, and here is the final fix.
With a little trepidation I installed it in the Olivetti, and connected a VGA monitor, and powered it up. To my delight the VGA monitor fired up right away! I did need to change jumpers on the Olivetti to get it output to the VGA card but all seems to be working fine.
More tests will follow, but as I only have a basic MS-DOS 3.3 boot disk presently, these will probably wait until I can attach a hard drive, not easy as the Olivetti only has 8-Bit ISA slots, and short half height ones at that. Current plan is to build a XT-CF-Lite at some point.
Hi Darren.... did you ever get the Trident TVGA9000i model 7210 card working in your dad's IBM XT as well as the Olivetti? ... look forward to hearing all about it. Simon, York, UK
ReplyDeleteThank you sir, I bought a Trident tvga9000i-1 for my XT, and I did the same mod with great success. PCB is slightly different but got is working first time. Thanks again!
ReplyDeleteJust wanted to say thank you for posting this information. I was able to successfully mod my Trident 9000i-3 to work on my XT clone!
ReplyDelete