VOGONS


First post, by LuigiThirty

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I picked up a Tektronix K1103 protocol analyzer recently because it’s full of transputers. Once I got a peek inside, though, it was clear that it was also going to be super upgradeable. No less than six ISA slots in a portable chassis!

But... it seems to be unusually slow despite my upgrades, according to the big benchmarks. I’m thinking it has something to do with the motherboard, which I can’t find any info on.

https://imgur.com/a/OSrGeTw

The motherboard is a Microdesign SC i486 Rev.A4. It has a VLSI VL82C486 chipset and an Award Modular BIOS 4.20. It came with a 486DX, I dropped in an Am586 133MHz. It’s identified by the BIOS as an “Unknown-50” but CHKCPU confirms it’s running at 133 (33MHz FSB and 4x multiplier).

I installed a GD5426 video card, a Sound Blaster 16, and an NE2000 NIC. (It also has three Siemens transputer cards that have no info online.)

Even if I pull all the cards except for the video card, I get 32.2FPS in 3DBench and Doom doesn’t even run at full speed? According to the benchmark spreadsheet, even with an ISA video card and no L2 cache I should be getting way more than that. I dropped in a 486DX2-66 (which the motherboard does recognize properly) and I get 27FPS in 3DBench.

Memory bandwidth is 31MB/sec according to CACHECHK and all the speeds seem fine.

Does anyone have any info on this motherboard or its jumper settings?

Reply 1 of 4, by Horun

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Those old beasts that the CPU was on a daughter card were never speed demons, just not the same as a standard AT style 486 board.

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 2 of 4, by cyclone3d

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What settings are available in the BIOS? Are there any wait-state settings?

What speed is the ISA bus running at?

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Reply 3 of 4, by LuigiThirty

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cyclone3d wrote:

What settings are available in the BIOS? Are there any wait-state settings?

What speed is the ISA bus running at?

Basically no settings in the BIOS, unfortunately, just shadowing and cache setup. There are a few jumpers on the board but I can’t work out what they do. There’s no docs for this board anywhere online.

The ISA bus runs at 8MHz, I believe? I found the data sheet for the chipset and it says it’s configurable in 2MHz increments 8-16MHz.

I have a Pentium 90, but I thought having a souped up 486 portable would be neat. It works well enough in Windows 3.1 and with most 2D games I’ve found at least.

Reply 4 of 4, by evasive

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MicroDesign became DigitalLogic in 2001:
https://web.archive.org/web/20010418173741/ht … rodesignco.com/
They have exactly ZERO information about MicroDesign products in their entire archive.

DigitalLogic became a Kontron company in 2010:
https://web.archive.org/web/20100406141537/ht … c.com/index.php
Since there is ZERO info from Digital Logic there's also ZERO information at Kontron...