Ok, got the video memory OKI chip, but I also got me 2x512KB zip memory for a total of 2MB.. hopefully.

I tried adding one of the zip memories, and VRAM jumped to 1MB. Yay! Then I added the other zip memory but VRAM remained at 1MB.. so I thought maybe it's not a supported configuration (1.5MB).

So, removed the zip memory, and soldered in the OKI chip, and I immediatelly got 1MB VRAM reported, and testing the video modes that need 1MB worked successfully (e.g. 640x480 16Mil colors).

Next, I installed the two zip memories, which should jump total VRAM to 2MB. Alas, only 1MB was still being recognized.. big bummer...

I suspected that a jumper might be needed to enable 2MB, so I focused on jumper JP I, which is next to the VRAM sockets and the Cirrus Logic chip. The jumper documentation only mentions JP I as used for enabling/disabling the on-board VGA chip.. but the jumper block is much larger than just the enable/disable setting, so I thought it's most probably under-documented. After some careful testing, I found that the odd row is used for enable/disable, while the even row of the jumper block is actually for VRAM size control. Indeed, bridging pins 4 and 6 results in 2MB VRAM. It gets recognized in WHATVGA and SpeedSys. I now have access to 1024x768 hi-color (64K), and even 1280x1024 256 colors.
VESA extensions also are able to find those 2MB modes and use them correctly.

So yeah, I'd say it's a success. I couldn't stand a DX4 with just 512KB VRAM.. 1024x768 at 64K colors is very nice for Photoshop and CorelDRAW 4 or 5 on Win3.1 🙂

Woohoo congrats. Glad you got 2MB I would have guessed the zip and SOJ to be in parallel, alternative parts. I think I'm only going to bother with 1MB though, don't need it to have great windows performance at higher res.

Indeed great to read your success, good work.

Good morning, and thank you for the information provided earlier. I have the same motherboard in a PC that looks practically brand new; after replacing the DALLAS chip, I couldn't figure out how to access the BIOS—it turns out you simply press F1 at startup. Now I need to figure out how to enable the second IDE channel.

wbahnassi wrote on 2025-08-22, 14:49:

[...]

I now have access to 1024x768 hi-color (64K), and even 1280x1024 256 colors.

Nice 😀

Non-interlaced or only interlaced? With a 5428 I'd sadly only expect the latter...

So yeah, I'd say it's a success. I couldn't stand a DX4 with just 512KB VRAM

That's not VRAM, GD-5428 only supports DRAM.

Efo74 wrote on 2026-08-15, 07:06:

Good morning, and thank you for the information provided earlier. I have the same motherboard in a PC that looks practically brand new; after replacing the DALLAS chip, I couldn't figure out how to access the BIOS—it turns out you simply press F1 at startup. Now I need to figure out how to enable the second IDE channel.

Entering the BIOS is only possible after a cold reset. Best is to just power-off then power-on again. During POST with the big Blue Lightning logo on the screen, a small square with squiggles in it will appear near the bottom-right corner of the screen after a few seconds. This is the cue to press F1 (or I think any other key even) to enter the BIOS. Just hit F1 and wait a little bit more. The POST process will finish counting the memory then enter BIOS setup.

On a soft reset (Ctrl+Alt+Del) you don't get the small square to show, so no matter what you press it will be ignored.

wbahnassi wrote on 2025-06-26, 01:20:

I'll try to give it a run when I put the previous HDD back.

wbahnassi wrote on 2026-09-24, 09:56:

The God-knows-what-CPU-is-this system 😅

Did you ever get round to trying my SIV utility on it?

Looking at https://theretroweb.com/motherboards/s/alaris … obalt-lpx-rev-a I wonder, how much memory does the system have and can it have > 64MB? Given it takes 72-pin SIMMs I wonder if 128MB is possible.