According to this list I found in the Netherlands the only way to run a DX4 would be placing an overdrive processor:
http://www.tulipgv.nl/leden/upgrade.htm

For the rest I couldn't find much in a fast search.

I think it will support 3.3 volt processors, cause i see a VRM on your motherboard on the left down where normally a flat pack soldered 486 is installed.. You only need to know which headers you can control that VRM with..
Also all 486 PCI motherboard will support 3.3 volt.. Only the first 486 ISA motherboards and first period 486 / VLB motherboards do support 5volt only.. But with a PCI board it should support 5v / 3.3v / 3.45volt perhaps also 4 volt.

I only dont see any benefit of installing 64MB of memory on your system.

20MB is already plenty enough, specially with windows 3.11 wfw.

And dont forget that there is already a Cirrus logic graphics card on your motherboard. I think its the CL-5438.

Here is a link to the manual: http://hnw.info.tm/tulipsite/downloads/manual … oard_manual.pdf

It support a 80486 DX4-100 max.

Thanks a lot!

Yes, the Cirrus integrated video is present, but it is just 1 MB and the additional memory slots are weird so I don't think I will upgrade. I did put Ati Rage II+ PCI instead, booted up nicely, also Creative AWE32 PnP.

Regarding 64MB, I have bag full of SIMM memory, might as well max it out 😀

Now if I could only find that 256 kb COAST module for it 😀

Hi All,

the link for the manual, provided by "seob" above, does not work anymore. Did anyone download it by chance and can share it again?

I have the same system and would like to mess with a different CPU.

Thanks

Hi peda126,

if you are still looking for the manual you can download it from web.archive.org.
https://web.archive.org/web/20180107113509/ht … oard_manual.pdf

If that doesn't work for you I can give you a copy. Have downloaded it some time ago.

Please be aware that there are several different versions of the TC40 mainboard, sometimes referred to as Level 1 to 5 (written in copper above the cache socket). There's also a label next to the RAM slots that says "TC40 Bxx" where xx can be e.g. 11 or 20. I have seen two or three different numbers there already.
The main point is that it is possible that your specific board only supports 5V CPUs, like mine did (came with a Pentium Overdrive 83MHz 😉. This is because they omitted the 3.3V regulator (a 3pin TO-220 next to the QFP-196 CPU socket) and some passive stuff. Luckily, this can be added without problems. You also have to set the according large jumperblock next to the brown fan header/PSU connector to the left side, otherwise the CPU will still get 5V from the PSU. Alternatively they have added a six pin connector like the ones for the PSU right next to the jumper. There you can input 3.3V (or whatever you like) as well (3 pins Vcc, 3 pins ground).

On my board there's a AMD DX4-100SV8B working right now. Although the BIOS doesn't tell the right name at the boot screen it works without problems as far as I have tested it.
There's only one little thing I might fix some day: due to different pinouts of 486s (intel, AMD, cyrix) the CLKMUL pin (pin R17 of socket 3) of the newer ones isn't connected to a jumper or anything (at least on my board revision) leading to the fact that you are fixed at a x3 multiplier on those CPUs (since they want a specific level on that pin for setting the "correct" multiplier which the board doesn't supply). That means for example that a AMD DX2-66SV8B runs at 3x33MHz and not 2x33MHz as it should (has internal pull-up -> x3, needs external ground for x2, tested). A DX5-133 would also run at 3x33MHz out of the same reason (internal pull-up -> x3, needs external ground for x4, untested).

If you don't want to modify the board there are also some cheap socket adapters with onboard voltage regulator and multiplier jumpers which also work fine. The only downside is that they don't have a ZIF socket for the CPU...

Another difference between the board revisions is that some jumper headers are sometimes not populated. Instead the jumper pins are hardwired on the backside of the PCB. I tried to figure out their specific function but due to a lack of freetime I could not finish that until now.

By the way: because I was not able to find any suitable cache module I started designing a 256kb cache module on my own. Don't know if this will be working in the end and being worth the effort at all, but at least you can learn something whith such things 😉
Don't expect it to be ready too soon, as I can only work on it from time to time.

Regarding the video memory upgrade:
As far as I could figure it out it would require two 512kbyte/4MBit memory ICs in a very odd package.
This is called "zig-zag in-line package" oder "ZIP" (Amiga users may have heard of it before). Although the manual mentions it at some place I didn't realize how this upgrade should work for some time (mainly because I had never seen such a package in over 15 years of designing electronics and could not figure out how to connect any memory to that strange sockets).
Unfortunately these RAMs are very expensive today if you can find any at all and I don't know the exact type required. They are also very large blocking the PCI slots in the end, so I decided not to go after it anymore.

Quite a bit of information, but maybe it helps someone...

Regards

(P.S.: I am new to the forum so if I did something wrong regarding posting rules please give me advice and be patient. Thanks.)

Hi ChrisK,
thanks for your brief explanation!

My board is a TC40-B20 and it supports 3.3V CPU just fine. The PSU provides the 3.3v. This computer was made by UNISYS, model CP4663.

By now i have my system up and running. I use a AMD 5x86 P75-133 CPU but it only clocks at 100Mhz in my system and is detected by the BIOS as an DX4. I set the jumpers for an DX2, since i read the AMD5x86 doubles the set multiplier internally to run with 4x33. But obviously he doesn't. Looks like i need to look into the mod you explained??
I have a second TC40 motherboard that i could use to test the modifications. The only thing with this one is, the IDE and FDD controller are not working anymore since I installed the CPU in the wrong orientation. 🙁 . But with a ISA IDE controller installed, the board boots just fine.

I happen to have the original cache module. If you need me to send you some information about it, let me know. Maybe we can reverse engineer it?

I decided to don't mess with upgrading the memory of the internal GPU. I will install a PCI graphics card.

Regards

Hi peda126,

let me know if the multiplier thing works if you happen to mod it on one of your boards!
I didn't have time to test it until now. A small patch wire from CLKMUL pin to Ground should be all that's needed (or may be a jumper or DIP-switch if you like to use other CPUs at some time).

Could you send me some pictures of the cache module? Is it labeled by Tulip or do you see any other markings of the manufacturer on it?
I know of two types made by another manufacturer (one 128kB and one 256kB) that should work (made for that exact Intel chipset and also the pinout fits to the TC40s connector) but I'm also curious if Tulip made their own ones.

What bus clocks does your boards support? Is it 25MHz & 33MHz only or can you also set e.g. 40MHz?
And do you know if your boards support Cyrix/IBM CPUs?

Regards,
C.

Hi ChrisK,

Here are the pictures of my cache module. its a 256k, as far as i know.

I will try the motherboard mod if i have time and let you know.

I think my board only supports 33mhz bus. (maybe 25, i dont know...)

regards

Oh no, there's a PAL IC on this cache, that squashes ease of cloning a cache module.

Cheers,

Nice! That confirms my findings 😀

A little preview of my design. Without PAL...

Great to see this thread alive!

I got 3.3v CPU's working nicely on my TC40 board but no luck with cache module. If anyone would sell one or the newly developed one would work it would be awesome 😀

Never put an URL as download, because they can dissapear over a sort time..

I`ll put the file here as future reference (before archive gets lost(

Hi ChrisK,

i was looking in to the mod you mentioned above for the multiplier, but i have some concerns, or dont understand it completely.

You say a AMD DX2 would run at 3 x 33, without the external ground. But my system came with an Intel DX2-66 and it worked fine at 66Mhz.
Now i am running a AMD 5x86 133 CPU. I only changed the jumpers to supply it with 3.3V. All others are for the DX2. This CPU is clocking at 100Mhz (3x33) now.

If i understand you correctly, the DX2 should not run at 66Mhz without the added ground wire? Why would the DX run with a x2 multiplier and the 5x86 with x3?

BR
Peter

OK, let's have a look into this:

Intel DX2 don't use the CLKMUL pin (only DX4 do: LOW=x2, HIGH/unconnected=x3) but have their multi fixed internally to x2. That's why a INTEL DX2 runs @ x2 regardless of CLKMUL setting.

The (enhanced) AMD DX2/4/5 CPUs use CLKMUL but interprete it differently each:

The DX2 wants CLKMUL=LOW/grounded for x2. If it is not grounded it is per AMDs datasheet undefined but it seems that it runs at x3 instead. That must be why my DX2-66SV8B runs at 100MHz without any special setting on CLKMUL.
The AMD DX5-133 runs at x3 for the same reason: it wants CLKMUL=LOW for x4 and with CLKMUL unconnected (or at HIGH/Vcc) it runs x3.

My GUESS is they all have an internal pullup on CLKMUL which let's them run x3 if CLKMUL isn't set externally.
I'm pretty sure i have read somewhere that there acutally is a internal pullup but I can't find it now. That's why my guess here. Sorry for that.

I hope this is somewhat understandable.
If you want to be secure just use a 1k .. 4k7 resistor instead of a pure patchwire from CLKMUL to ground. That should overwrite any internal pullup but also limit any harmful current. But there shouldn't be any since CLKMUL is an input.

I have added some pictures from an AMD datasheet (number 20736B), a ST application note, as well as an AMD 486 demonstration board schematic.

Regarding the cache module: let's see how it works out. If it runs I'm sure there will be some PCBs over if someone is interested. If not, don't be too disappointed. I'm going to order the PCBs in the next days...

@ Robin4: OK 😉

Found it!
-> AMD document no. 19751C

Hi Chrisk,

Thanks for the explanation, I tried it today an it works like a charm. I ran a patch wire from ground to the CLKMUL (R17) pin on the 5x86, with a 1k resistor.
On the POST screen it identifies itself as "unknown processor @ unknown speed". But if I run the program chkcpu.exe he identifies itself correctly as 5x86 @ 133 Mhz.

The specs of my machine right now are:
- AMD 5x86-133
- 256 KB cache module
- 32 MB RAM (I have two 64MB sticks installed, but the Bios sees only a total of 32MB??)
- IDE SD adapter with 16GB sd-card, with dynamic drive overlay. (the bios has the 528MB limit)
- Matrox Millennium II PCI graphics card with 8MB
- FDD & CD-Rom
- Creative Labs Sound Blaster Vibra (CT4170)
- on-board NIC, to browse the internet 😉
- Windows 95 R2.5

Overall I think I have a quite powerful 486 system now!

I also have an original IBM AT, 386 compatible, 486 DX2/50 laptop and a homemade 8088 with Sergey Kiselev's PCB's!

Thanks,
peter

Hi peda126,

great to hear that it works! Also nice soldering skills. You must have done that before!?
The BIOS is quite restricted in terms of known CPUs. But as long as it runs...

As for the RAM issue, I have two 16MB sticks installed which work alright. I must have two 32MB sticks somewhere, if I find them I can give them a try.
The TC40 manual says it supports up to 64MB (which is what the chipset can cache with 256kb of cache memory) and the chipset itself can work with max. 128MB according the datasheet.
Maybe this is some bank or addressing limitation or the memory chips' density is too high. Do you also see 32MB with just one stick or does it reduce to 16MB?

Regards,
Christian

Hi ChrisK,

if I remove one, it reduces to 16MB. I bought this two 64MB sticks brand new of Ebay.
Maybe i need to get old 32MB sticks.

Peter