A2386SX upgrade processor swap question

[tiim]

The "2+" parameter for cache486 tripped me up, it works! SI over 70 now, wow! (Thanks @BlindGerMan)

Thanks also to @nobodyii for helping me find the cache486 utility.

For clarity among all following along:

I had the original Intel i386SX-20 chip swapped on my A2386 for a 3.3v TI486SXLC2-G50-PQ and CPU oscillator changed from 40.0 MHz to 50.0 MHz (Thanks @Pior)

I added a heatsink and fan, designed for a Raspberry Pi. The Bridgeboard supplies 5VDC VCC to the CPU, so it does get hot. Installed the heatsink/fan via adhesive conductive pad direct to the top of CPU. Installed 5V fan points from capacitor C322 (left side is VCC, right is GND) on the bridgeboard.

I went through the Janus setup and floppy cabling/jumper instructions in the original A2386 manual. (available on the Internet Archive) My target machine is an ECS A2000 with Kickstart 2.04/WB 2.1, A2630 accelerator board, A2091 HDD controller, SCSI2SD v5.1 2GB drive and Chinon FB-357A HD plus Gotek floppy drives as DF0: and DF1: respectively. The bridgeboard, if using the dual cable and Flipper software is keen to the DS0/DS1 jumpers on your FDD, make sure they are both set differently!

After the board was installed, and Janus installed (Get the absolute latest Janus from Aminet, it contains a few bug fixes), a 32MB autoboot HDD file created on the Amiga side, Flipper is used for internal shared DF0:

I connected a VGA card, (Diamond Speedstar Pro 1MB) connected separate (from 1084) VGA monitor and started the PC.

Configure the PC BIOS for HDD = NONE (if using hardfile) and FDD A: to whatever DF0: is. (1.44MB for mine) Set the date and time if you have a clock battery on the BB. It is also noted that if you have a clock doubled CPU, set the Bridgeboard to "slow" speed. Save and exit the BIOS configuration, reboot.

I installed the full MSDOS 6.22

After DOS installed, I made a folder on the C drive called "Janus" and placed the Janus tools (amouse, aread, etc.) in there. this is all in the manual. If you ever need to edit the BIOS settings, the "BBSETUP" utility is there.

Now, for clock doubled processors like mine, I downloaded two more utilities, one from this thread (or elsewhere), one from Aminet.

The tool from this thread is called CACHE486.EXE and if I may (mods might delete this link) link to a Vogon's discussion where the file is linked:

Doom on the 386 and 486DLC - Page 2 \ VOGONS

www.vogons.org

The other tool is on Aminet, called BBCPUCLK.COM

Download these two files (BBCPUCLK is 59 bytes, CACHE486 is 12kib) and place them under your C:\Janus folder.

In DOS, edit your autoexec.bat file. Include the Janus path "PATH C:\DOS;C:\Janus"

Still in your autoexec.bat add the following two lines exactly as printed at the end:

bbcpuclk.com
cache486 2+

Reboot your PC via CTL-ALT_DEL

Everything should be working correctly now. I used "Norton Sysinfo v8" to get a cached/doubled CPU score of 70.5 which is around the speed of an i486DX-33 (note: SI will report the CPU as a "Cyrix" if you have a TI. The benchmark score and CPU reported speed are the correct indicators here)

Thank you all on this forum for following along and helping me. I hope my instructions are useful. @A4000Bear's web pages about overclocking were also invaluable.

For even more speed improvement, installing an IDE drive is next. I have to solder on the 16-bit IDE slot extensions first!

Cheers,

Tim

 

[vojake]

I also wanted to do the conversion. Everything ran for about 30 minutes with the original 40 MHz oscillator. After the conversion to a 66 MHz oscillator, the board seems to have died.
It no longer beeps at startup and the VLSI gets very warm. The CPU remains cold.
A reset to 40Mhz and the original CPU did not bring any improvement.
I suspect that the VL82C311 has died. Does anyone have any tips?
@nobodyii Were you able to repair your defective A2386? Did you get the VLSI on the internet?

 

[BlindGerMan]

The VLSI chips are quite rare, but I never heard, that this chip died!

 

[Xanxi]

One of the VLSI was dead on an A2386 that Hese fixed for me before.
Apparently, these chips can be bought from China.
If your board has died, the best person to fix it is Hese.

 

[vojake]

Here I am back with news
With some testing i found out that there was no oscillator-signal, the 5V line of the 40MHz oscillator was interupted. I fixed it and now the card gives beep codes at startup.
3x1slow and 2x fast.
In phönix bios code that means, the slave dma register is defect.
Is this a sign that vlsi is really faulty?

 

[vojake]

Meanwhile VLSI VL82c311 chip is successfully changed, but same issue.
Beeps are same.
This beeping in phoenix Bios means "Slave-DMA-Register defect"
Any hints to find the DMA error ?
Many thanks for the support