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How is the S3 928 SVGA chip on a PS/2 model 76i connected?

thisisamigaspeaking

thisisamigaspeaking

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I believe all 76, 77, 76i, 77i, 76s, 77s are the same in this regard?

How is the S3 928 connected to the system? I's a VLB/EISA chip I believe, does it have a 32-bit connection to the system on a PS/2? How is the performance?
 
Reading the sketchy IBM docs it looks like its interface is effectively VLB and it should perform accordingly? That said, I’m definitely the wrong person to be answering this, I’ve never used a PS/2 more modern than a 55sx.
 
GiGaBiTe said:
The S3 928 is tri-bus (VESA, EISA and ISA.) https://www.dosdays.co.uk/media/s3/928/86C928_Datasheet.pdf

I supposed you could look for the 74ALS245 bus transceivers and see where they go from page 1-1 on the datasheet.

Benchmarks would be another, but you'd need to find a baseline of the ISA version to compare it to.
Click to expand...
Possibly count the number of 74ALS245?

Given that the 76 and 77 represent IBM's attempt to "do things right" I would be pretty surprised if they weren't VLB. Otherwise, it would've made more sense to put XGA-2 in the systems I think. It would've been a step backward to shoehorn an ISA-only SVGA into an MCA system.

Comparing Doom performance on the same system to XGA-2, and against other DX2-66 (in my case) benchmarks, may offer some insight.
 
thisisamigaspeaking said:
Possibly count the number of 74ALS245?

Given that the 76 and 77 represent IBM's attempt to "do things right" I would be pretty surprised if they weren't VLB. Otherwise, it would've made more sense to put XGA-2 in the systems I think. It would've been a step backward to shoehorn an ISA-only SVGA into an MCA system.

Comparing Doom performance on the same system to XGA-2, and against other DX2-66 (in my case) benchmarks, may offer some insight.
Click to expand...
Look at figure 12.7 in the datasheet for the local bus configuration.

IBM doing something right? I tried a few Lacuna 9576 or 9577, the S3 86C928 seemed to be a kludge.

I heartily believe a 2MB XGA-2 could have been a far more stable video solution.

Lacuna Planar has the files and whatnot. Never really dived into the 86C928, it seemed more of a lost cause than the best solution...
 
IBM sales material for the machine describes the video as “local bus”, so unless you have specific reasons to think they didn’t just slap it on the 486 bus upstream/parallel to the MCA bridge (a configuration the 86C928 supports, because that’s all VESA local bus is) that seems like the most likely situation.
 
I have my 76i upgraded with a DX4/100 and even more complex 3d DOS games are running well. Certainly not connected to ISA. But the 86C928 is also not the best SVGA chipset either, so don't expect miracles.
 
Timo W. said:
I have my 76i upgraded with a DX4/100 and even more complex 3d DOS games are running well. Certainly not connected to ISA. But the 86C928 is also not the best SVGA chipset either, so don't expect miracles.
Click to expand...

I'm thinking of going with an AMD X5-133. Did you need to do anything other than install a VRM in the system to get the DX4 to work? Do you have an L2 cache module?

I'll benchmark the system against an XGA-2 and perhaps with some different processor/cache configurations.
 
I used an OverDrive CPU, so not even a VRM was needed.

Yes, I have the L2 cache module.

I have the system set-up and ready to go. Let me know if you want me to do any benchmarks as well. :)
 
This system turned out to be pretty nice, it's got a WT/WB switchable 256K L2 Cache, 3.4V VRM, DX4-100 CPU, late revision planar. I believe this is the original configuration of a 9576-ATB. Basically saved me some potentially costly upgrades (especially cache module).

Briefly had an issue with a hard crash and then blank screen on restart, but it is working again. May need to be cleaned. I understand there is one cap (C68) that is particularly prone to leaking as well.

Looks like it is VLB. I have not run Doom yet, going to switch over to CF drives (and test McIDE-CF vs. the built-in IDE).

hwinfo-1.jpeg
hwinfo-2.jpeg
 
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