ph4nt0m: IBM 486BL3 (486DLC3) on 386-to-486 Upgrade Adaptor

[ph4nt0m]

This is probably the fastest 386-to-486 upgrade adaptor out there. The CPU is an IBM 486BL3 rated at 75MHz with 16Kb write back cache. There is also a Cyrix 87DLC 33MHz math coprocessor. Plugs into a 386DX socket.

The adaptor is I-O Data PK-A486BL75. It was made for Japanese PC-98 machines like PC-9801RA with a 20MHz 386DX, but it works in many regular PCs. The adaptor can optionally double input clock, so 20MHz turns into 40MHz to both the 486BL3 and 87DLC. The 486BL3 can also double or triple it internally.

Looks like new. I have tested it in an AST Premium/386 mobo made in 1987 or 1988, not sure.

PM me reasonable offers.

[stamasd]

Interesting. Is there any documentation for what the DIP switches do?

[feipoa]

I have some documentation on the DIP switch. This is an IO DATA Power up kit for PC-9801DA, RA, and PC-98RL. Model number is PK-A486BL60 or PK-A486BL75.

Default DIP Switch settings are all off.

SW1 = Hardware memory flush function for I/O operation
ON = DMA + I/O read/write
OFF = DMA only

SW2 = PCB-based additional clock doubling (not on CPU) feature, aka "turbo" mode
ON = Turbo mode 2x (e.g. if the IBM CPU is in 2x mode, this will give you 4x total)
OFF = Normal mode 1x (use software to set the CPU's multiplier between 1x, 2x, 3x, e.g. using PK486BL.COM)

SW3 = Enable/Disable onboard co-processor
ON = Coprocessor disabled
OFF = Coprocessor enabled

SW4 = not used

Some settings in config.sys for (don't ask me about these, it has been too long and these are from my notes. I suggest using the Evergreen setup program anyway)
DEVICE = PK486BL.COM
/I
/R
/B
/F
/N
/T {1,2} turbo
/{1,2,3}
/S
/LMCR=xxxx, e.g. /LMCR=00FF
/LMROR=xxxx, e.g. /LMROR=0000
/CMLR=xx, e.g. /CMLR=D0

[feipoa]

ph4nt0m, did you test it with SW1 on or off? What software did you run for testing? Many motherboards need SW1 on to run properly, which is not ideal for performance.

[ph4nt0m]

[feipoa]

I have found the IODATA unit not very forgiving for IBM-based systems without SW1 set to ON. Cannot even run DOOM. The Buffalo branded unit (no jumpers/DIP), on the other hand, was more forgiving for some reason and I was able to run DOOM, but I had to spend days fooling around register settings. I wonder if these IBM BL3 chips could run on standard IBM PC's without all the PLD chips on the PCB - that is, if they were to be removed and the pins were wired straight through the PGA. Though i'm not sure if we have the pinout datasheet on the BL3 chips...

[ph4nt0m]

The IBM 486SLC2 / SLC3 is pin compatible with 386SX, voltage is another matter. It's a good question if 486BL2 / BL3 is pin compatible with 386DX. The VRM supplies 4V though.

[feipoa]

If anyone has the BL3 datasheet, I might be willing to hack the PCB of one of my Buffalo or IODATA modules to bypass the onboard logic.

The Buffalo unit I have contains only a single GAL, so it would probably be easier to re-route, while the IODATA has 3 PALs. From what I could discern, only 6 pins on the Buffalo's GAL are connected. For the rest - six pads were grounded, while some I couldn't determine where they went, possibly left floating (checked all connection points on the PCB). Aside from pull-ups, Vcc, and reset, the GAL may only be connected to CLK2 and ADS#.

[nicetux]

Is it still available? I am interessted, please send me a PM, thank you.

[debs3759]

haha, sellers asks interested buyers to PM him, so potential buyer says "no thanks, you message me"

[feipoa]

Unique strategy. I wonder what the benefit is this? Hide selling price? Is going to be so high?

[Marcin]

Some people are to shy to make private offers or do not have time to play on this way. It is easier to put seller's max and drop it eventually.

[ph4nt0m]

More tests. The CPU runs fine at 100MHz (4x25MHz). It needs a larger heat sink for such speeds probably or some active cooling.

With the coprocessor enabled:



With the coprocessor disabled:



Norton SysInfo:

[debs3759]

So the processor benchmark without the FPU is triple what it is with? I didn't expect that

[kixs]

It's the usual bug