A2386SX upgrade processor swap question

Can anyone tell me what the BBCPUCLK software does exactly that stops the crashing? I'm running into this with another system, and I'm wondering if whatever this does might work for what I am running into as well. The issue I'm running into is apparently some kind of strange BIOS limitation.
 
Last edited:
BBCPUCLK reconfigures the CPU clock circuitry in the A2386. Apparently the 486SLC chip does not like the clock provided to it by the Bridgeboard, especially in clock doubled mode. Possibly the logic used in the bridgeboard is not fast enough. There is more information in the documentation with BBCPUCLK http://aminet.net/package/misc/emu/BBcpuclk1.0

Aminet also has some information on 486SLC chips, including an optional modification to improve performance: http://aminet.net/package/misc/emu/BBCpuUpgrde1.0

How to overclock a bridgeboard with a 486SLC upgrade: http://members.iinet.net.au/~davem2/overclock/a2386.html

How to upgrade a bridgeboard to 16MB http://aminet.net/package/docs/hard/A2386_16MB
 
@oldskool1, sorry for bumping your old thread, but i'm curious as to how your ti486sxlc2 is running today? The reason why is because I want to possibly try to use one in a 386sx Amstrad Mega PC.. but I read conflicting info on its input voltage. The G50 model should be 3.3V power but 5V I/O compliant.. I've read that the O50 variant which is 5V Power compliant came off the same production line and all Ti did was badge the ones capable of running 3.3V as G50 and the rest for 5V O50. On the other hand i've read how its only the first batch that where such and all later ones were 3.3V only...

I'm cautious to try because of the uncertainty..
 
Last edited:
Phipscube said:
@oldskool1, sorry for bumping your old thread, but i'm curious as to how your ti486sxlc2 is running today? The reason why is because I want to possibly try to use one in a 386sx Amstrad Mega PC.. but I read conflicting info on its input voltage. The G50 model should be 3.3V power but 5V I/O compliant.. I've read that the O50 variant which is 5V Power compliant came off the same production line and all Ti did was badge the ones capable of running 3.3V as G50 and the rest for 5V O50. On the other hand i've read how its only the first batch that where such and all later ones were 3.3V only...

I'm cautious to try because of the uncertainty..
Click to expand...
I know this reply is very late, but it still may be of interest.

Yes, the G50 version of the TI486SXLC2 is rated at 3.3V nominal power. According to the datasheet, the maximum rated voltage is 5.5V. I'm not aware of differences between earlier and later G50 variants.

I have had my G50 TI486SXLC2 on my A2386 bridgeboard for well over 20 years, and it has worked fine. It was even overclocked at 62MHz for much of that time. The chip does get hot, though not too bad at its rated 50MHz. I would still advise gluing a heatsink on it, with some modest airflow. I have a small, quiet 5V fan attached and that is enough to keep the heatsink cool to the touch.

Given the maximum rated voltage is only 0.5V over the voltage in the bridgeboard, I would advise measuring the 5V supply on the bridgeboard to ensure that it is no higher than 5V. Preferable if it is slightly lower. Mine is 4.86V which is pretty much ideal, not too low to be a potential problem for stability.

I mentioned before I was running at 62MHz. This was the absolute maximum I could run the bridgeboard without too many problems. Since then I have reduced it to 56MHz, mainly because I found an FPU that actually works with a clock doubled TI486SXLC2 chip on an A2386SX. It was rated at 40 MHz, and 56 was the highest I could reliably go with it.
 
Yes i concur with this, it works 100%. The 3,3V / 5 V debate was bullshit spread on the internet which prevented me for years to upgrade. It just works. Mark my word people from the future : IT WORKS.
However, i am not fond of overclocking on top of that. Bridgeboards are rare and precious, don't damage them to gain nothing except a longer line in norton sysinfo.
There will be a limit to what the board can do because the bus is still 16 bits of the 386sx.
 
Ti upgrade working fine here for 5+ years on a GG 486SLC at 50mhz. Agreed, the voltage thing does not appear to be an issue long term.
 
Which FPU can work in clock doubled mode?

I am in the USA and contacted @hese about doing the work on mine. Not sure if anyone in the States has the skills and equipment to to the CPU swap. Yes, Bridgeboards are rare and expensive and I'm worried about sending it twice overseas...
 
unsure. the Cyrix FasMath CX 83S87 -25-JP i had died after a while with the cpu running clock doubled at 50.
 
About FPU, two things.
1/ i have never encountered problems with FPU with any of my bridgeboards, even with clockdoubled Cyrix/TI, and i have used Intel, Cyrix Fasthmath and ITT ones, so i am not sure there would be a problem, or even that the FPU would be clock doubled at all. There has been a lot of internet legends about the bridgeboards which have proven false in time.
2/ the FPU is utterly useless anyway. If you are not into excel or specific math stuff, i don't see what you could do with a FPU with a 386/486 class bridgeboard. In my case, i was just a matter of not liking empty sockets.

Hese is the best. He has vast knowledge of these bridgeboards, either A2386 or GG386/486. For the GG, since we understood how to fix the faulty Vortex FPGA i believe the GG could be fixed from any fault, Hese has done it for me. If you just want to solder the CPU, someone closer to you might do it too.
 
Last edited:
Did you enable Cache and Clock Doubling ? seems it runs only at 20Mhz

The Benchmarks don`t look like Cache is enabled.
 
tiim said:
Which FPU can work in clock doubled mode?

I am in the USA and contacted @hese about doing the work on mine. Not sure if anyone in the States has the skills and equipment to to the CPU swap. Yes, Bridgeboards are rare and expensive and I'm worried about sending it twice overseas...
Click to expand...

This site lists three different FPUs that work on a clock doubled A2386 SX with 486SXLC2 CPU: https://a4000bear.neocities.org/overclock/A2386/A2386
 
Does anyone know the proper 5V and GND pins to add a CPU fan to the A2386? I see that C101 (left side) is VCC for the CPU (mine is a 486SLC) and I know where the GND pins are on the Zorro slot. Just asking if you have prior experience putting a 5V fan on this card.

Thanks.
 
Don’t know but a simple heatsink is sufficient in my A4000 even with clock doubled cpu and despite very bad airflow.
 
Xanxi said:
Don’t know but a simple heatsink is sufficient in my A4000 even with clock doubled cpu and despite very bad airflow.
Click to expand...
I figured it out. I tied VCC (left) and GND (right) to both sides of C322 at the top of the PCB (Right of the ZIP RAM)

Running all day so far.
 
OK, this thread seems to have some knowledgeable folks on it.

I posted on EAB as well. I am not seeing 50Mhz or the cache enabled on my TI486SXLC2-G50-PQ installed on the A2386. I installed BBCPUCLK from Aminet but I think I am missing another critical piece of software, it seems to have vanished on this thread.

Can anyone help?

Thanks,

TIm
 
Of course... Please remove .pdf
Don´t forget to switch system speed in BIOS to low. BBCPUCLK will change this setting when your A2386SX is booting.
 

Attachments

  • CACHE486.EXE.pdf
    11.8 KB · Views: 7
Almost there. Still a 25Mhz CPU speed, but cache is enabled now and at 39.4 Norton SI, little bit faster than a i386DX-33!

I set the CPU to low speed in BIOS.

Am I missing anything to clock double?

Thanks @nobodyii
 
You must log in or register to reply here.
Back
Top Bottom