Commodore 386SX Bridgeboard Hacks

[Jeff]

Here is my recently completed Bridgeboard with a coin cell hack, socketed oscillator, and a Cyrix 486 50mhz upgrade. It benchmarks about the same as the Vortex 486SLC-II 50mhz board!

A2386SX Bridgeboard

Does anyone remember Jordan Krim that wrote the A2386_16MB.lha file on Aminet? I was going to have a Zip to SIMM board made and do the upgrade but there is a discrepancy in the bios changes between the document and my Bridgeboard Bios as follows;

 From Jordan's document
ADDRESS     OLD DATA    NEW DATA
=======     ========    ========
73a7_____b4________ff


My A2386SX Original Binary Version 1.0
ADDRESS     OLD DATA
=======     ========
73a7_____e0

I wonder if it's a typo in the document or if there is more than 1 version of 386 Bios for 386 Bridgeboards? I tried burning it to an Eprom but the bridgeboard will no longer boot with the modified bios. Granted I haven't done the 16MB hardware mods yet. He sent me a working binary of the modified 16MB bios about 10 years ago but I seem to have lost it and I can't get a hold of him now. Has anyone done this mod successfully?

[LoadWB]

It kills me.  I had one of these 386 boards many years ago.  I got duped into paying some guy for a 486 bridge board, but had to sell my 386 to capitalize.  The 486 board never showed up and dude disappeared off the face of the planet with my $80.

Gotten much wiser since then.  And much 386 Bridge Board-less.

[rkauer]

 If it works, don't worry. Murphy's law.

[Plaz]

Maybe some day I'll find one and try the Cyrix hack. I have Cyrix standing by.

Plaz

[Jeff]

The point is the modified 16MB Bios won't boot in that board. Now maybe it won't boot without the hardware mods I don't know. I didn't really want to have a Zip to SIMM board made and fit the simms without a confirmed working Bios first and my file doesn't match the Aminet doc exactly.

Oh well, maybe Jordan will turn up and remember. Until then I'm happy playing with it as is. BTW I sold my first one also. It took me years to find another one that works. Thanks to the VintageAmigan for this one.

Jeff

[Zac67]

FYI: Cyrix 486SLC != 486 - it's more a souped up 386SX; 16 bit data bus, 16 MB max memory, far below scalar.

A real 486 (both DX or SX) has 32 bit busses, larger caches and is nearly scalar. Don't want to spoil the party, but a real 486 is a lot faster.

But: there is a TI486SLC, same design but larger cache (8KB instead of 1 KB) - if you want the fastest, that's the way to go. ;-)

[jkrim]

Hi Jeff,

I am probably way late to the party, but I was goggling my name and found this thread, so the answer (in case you're still interested) is as far as I remember, the BB won't boot without the hardware mods i.e. the new 16 MB ROM fix was designed only for 16 MB and not backward compatible with 8 MB.

Jordan Krim

P.S. I still have my 16 MB ROM, but since I accidently blew up my really sweet Evergreen 486 (triple clocked), I haven't used the BB much.  Haven't had a chance to try the 2X Cyrix 486 yet.

[Jeff]

Never too late!  Hey, how are you Jordan? I really could use a working binary of the modified bios eprom. I have (2) working 486 modified A2386's that could use the ram expansion.

Could you please send me a PM or something?

Thanks,
-Jeff

[jkrim]

Hi Jeff,

Sorry, what's a PM? Do you have the 16 MB simms attached to the BB and the wire soldered to the BB?

Jordan

[superbonio]

Does anyone know where exactly, and where there is an error in the modification of the BIOS?
 Or maybe you have someone ready to program EPROM file?
 That fight with this BB A2386SX and maximally I get 8MB, after modifying the BIOS from Aminet, BB card does not start.
 Please help, can somebody spreading ready, modified the ROM file.

[spirantho]

Hi, and welcome

It sounds like you've changed the BIOS to a different one to support 16MB RAM. Did you change the RAM using a SIMM to ZIP converter?

What BIOS did you program, and what do you use for RAM now?

If I've misunderstood the question, could you express it differently?

[superbonio]

So, yes, I made a SIMM ZIP adapter PS2 Aminet ( http://www.heiko-pruessing.de/projects/a2386ps2/a2386ps2.html )
 I added (MA10) (Simm19pin) to the resistor R205 according to the description http://cd.textfiles.com/amigaformat/aformat-29-19980709/-Seriously_Amiga-/Emulation/A2386_16MB/A2386_16MB.guide
 Physically, I use only one base at simm (U1)
 4MB SIMM memory (8pc. Bone on one side) is seen as 4MB
 8MB SIMM memory (16pcs. SIMM bone, 8 per page) is seen as 8MB
 SIMM Memory 32MB (16pcs. SIMM bone, 8 per page) is seen as 8MB

 I did modification ROM (BIOS) of the specification http://cd.textfiles.com/amigaformat/aformat-29-19980709/-Seriously_Amiga-/Emulation/A2386_16MB/A2386_16MB.guide and programmed the new rom.
 My original ROM was like in the first post, that is, other than it should be

 From Jordan's document
 NEW OLD ADDRESS DATE DATE
 ======= ======== ========
 73a7_____b4________ff


 We A2386SX Original Binary Version 1.0
 OLD ADDRESS DATE
 ======= ========
 73a7_____e0

 Unfortunately, with the new ROM including A2386SX card does not start with any simm memory.

 Mainly I mean if someone has finished, modified, and running the file to the programmable ROM chips to recognize 16MB RAM card?