VOGONS


First post, by RetrOli

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Hi Ladies and Gents,

I set-up the following system:
UM486/486SX Mainboard (UMC UM82C480 chipset)
upgraded the 256k of cache from 20NS to 15NS; Tags are original and also 15NS; no Dirty Bit as the socket for it was omitted
Intel 486DX-50
Targa Tseng ET4000AX
16MB of FPM RAM SIMM 30 (currently 70NS, 60NS on the way)
Soundcard based on Opti 924 (w/t AD1845JD and OPL3 Clone LS262)
I/O-Controller based on Winbond W83787F and W83758F
generic CF to IDE adapter and a noname 2GB CF Card rated at 120x

It is up and running, playing Wing Commander 2 was a joy, now I am trying to optimize.
RAM is currently running at 2 W/S with FPM Mode on - according to Speedsys 4.78 the throughput ist @ 66,68MB/s and slightly higher than 1 W/S with FP Mode off = 64,14MB/s. This is with BUS Clock Selection: CLKIN/6 = 50 / 6 = 8,33MHz.
1 W/S @ FPM on and 0 W/S @ FPM off produced system hangs.

Before the DX-50 I was running a DX2-50 and with BUS Clock Selection: CLKIN/4 = 25 / 4 = 6,25MHz BUS I was able to set 0 W/S @ FPM on which yielded >80MB/s according to Speedsys. However, 3DBench scores dropped from >32 tp 30.2.

Besides upgrading the RAM to 60NS modules in the hope of achieving lesser/lower W/S I'd love to achieve BUS Clock Selection: CLKIN/5 = 50 / 5 = 10MHz (or more...).
Until now, both the former, but also BUS Clock Selection: CLKIN/3 = 25 / 3 = 8,33MHz with the DX2 resulted in stalls after the initial POST when the mashine was looking for the HD. Therefore I suspect that the controller is somewhat touchy and thus the culprit.

Are there any recommended ISA Controllers that are known to be tollerable to BUS clock increases? Should I switch to a branded CF card (e.g. Sandisk)?
I guess an additional network adapter as a means to use XTIDE to make full use of the 2GB drive is not helping either!?

All tests above were done with the controller and VGA card only - but sound works with the "stable" settings from above.
CPU-Speed according to Speedsys is @18,89 (with both the DX2 and DX-50) which should be spot-on for a DX2-50. NSI 8.0 gives a score of 108 and PC Player Benchmark reports 8,6FPS

And I thought VLB is hard to push to 40MHz System BUS and above...

Reply 1 of 5, by Disruptor

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RetrOli wrote on 2021-12-21, 23:31:

Are there any recommended ISA Controllers that are known to be tollerable to BUS clock increases?

I've done my 16 MHz ISA tests with an Adaptec 1520B (ISA) and an ET4000 W32 (ISA).

Reply 2 of 5, by maxtherabbit

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I've used the AHA-1542B up to 12MHz with no issues. Also used the generic UMC multi IO/IDE/FDC cards at that speed with no problems

Reply 3 of 5, by BitWrangler

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In general, the later and more "surface mount-y" controllers work best at high ISA speeds, the usual thing to crap out first is the sound card or network card around 11 or 12Mhz. Have had no trouble out of anything but slightly ancient* looking I/O cards at up to 33/2, so you should not have trouble finding one to do 50/3, however, you'll be swapping sound and NIC until you find ones that hold on at 50/4 and they probably won't go further. VGA goes like the i/o, it's probably only 286ish aged ones that won't do high bus.

* hmmm hard to describe, larger boards, more through hole chips, look like they belong in a 286...

I'm prollabubbly gonna have to delve into fast 486 ISA configs again eventually, got 3 or 4 boards to mess with. Hope the better boards I'll get to first will leave me something for them.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 4 of 5, by pshipkov

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If you want FAST 486 ISA - Symphony Haydn based mobos cover that best.
UMC ones - not so much.
: )

retro bits and bytes

Reply 5 of 5, by RetrOli

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I am not exactly trying to build an ISA monster, just thought this would be a fitting home to my DX-50.
Actually I never intended to do a 486 ISA System, it was rather unintentionally - as usual:
I got the Board as part of a bundle, slapped together this Frankenstein just for testing - half expecting the board to be dead - the system fires up on first try and I am hooked 😁

Adaptec AHAs, huh? Never intended to go SCSI. I actually have one ancient controller in stock, just can‘t tell from the top of my head if it is ISA or VLB; it was rather wide.
Do you guys then tolerate those shrieking SCSI drives or do you use SCSI->CF adapters/configs of some sort?

I have to admit though that I am already falling in love with this system as it is this bit more responsive and smoother for retro-gaming my oldest and dearest titles (WC 1+2, Comanche, Strike Commander, Privateer) than my very first PC which I still own and use: SIEMENS P3D-M 386DX-25. Will probably reserve that one for CIV and DUNE-alikes…