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Reply 20 of 62, by Paadam

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My TC40 works just fine with two 32MB sticks (total 64MB), of course without COAST it is uncached..

Many 3Dfx and Pentium III-S stuff.
My amibay FS thread: www.amibay.com/showthread.php?88030-Man ... -370-dual)

Reply 21 of 62, by Paadam

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Messed with my TC40 for few days: original Quantum HDD was failing and I struggled to copy the contents of it in order to preserve factory Tulip WfW 3.11 installation. During trying to get around of installing Dos 6.22 from floppies I accidentally found out that TC40 happily boots from CD 😀
Not sure, maybe it is widely known but perhaps someone might find it useful.

Many 3Dfx and Pentium III-S stuff.
My amibay FS thread: www.amibay.com/showthread.php?88030-Man ... -370-dual)

Reply 22 of 62, by ChrisK

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Hi,
there are news regarding the cache module.

Short story: IT'S WORKING!!!

Long story:
I assembled the prototype already end of December with 128kB for testing, mounted the module, switched power on and ... nothing. No smoke, no POST, just nothing. Only the POST screen after another power cycle saying the last system power on was incomplete. And of course it was not using the cache module.
Ok, I thought, let's put it aside for the moment and rethink everything.

Almost two months later I found some time (and motivation) to think about it again. I now also had a scope I borrowed and checked all those signals of the data RAMs: data, addresses, chip selects. Everything looked fine.
So what else could be wrong: the design itself, faulty SRAM chips (these were desoldered from an old cache module, so who knows), something missing on the mainboard, the mainboard not supporting 128kB cache...
Some days later I decided to add the missing 128kB to the module without knowing if the SRAMs chips I still had were ok and configured it as 256kB.
Put it into the mainboard, powered it on and again nothing. Hmm.
So what about the TAG-RAMs, I thought. These were new ones since I had not enough old ones for a complete module. So I did not expect any trouble there.
I connected the scope again, switched power on (no POST of course) and checked the signals. Switched power off, and on, and ... oh wait what's that, the machine POSTs, and better, it says it's using 256k of cache. what's going on!?!?
Checked the control signals again, found the TAGs chip select is low, ok it must be low to work, but it's low all the time. Hmm, may be ok.
Had a look into my layout. Located the TAGs chip select, ok it's connected, but wait: only between the two TAG-RAM chips and not to the boards connector (which only grounds that signal, so it would be low all the time anyway). How could that happen? Cross-checked the schematic, and oh no, it's a bug. Two different nets that should be the same. One named #TCS and the other #TCE. This is how it will NOT work!
So patched this one, put the module back, powered the machine on and here we go!!! Full working 256kB level 2 cache.

Cheers!

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Reply 23 of 62, by ChrisK

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I have done some benchmarking to see the impact of the L2 cache.
I used the "DOS Benchmark Pack" from philscomputerlab dot com.
The system is: TC40 L4, on-board graphics (Cirrus Logic with 1 MB), 2x 16MB RAM, 512MB CF-Card, CLKMUL with Jumper to GND for x2/x4 multiplier, 256kB L2 cache.
Results are "without / with L2 cache / speedup in %".

Am486DX2-100SV8B @ 33MHz x3:
1) 3DBench 1.0c (Slower PCs) ______ 50,0 / 52,6 / +5,2%
2) 3DBench 1.0c (Faster PCs) ______ 47,8 / 50,0 / +4,6%
3) Chris's 3D Benchmark ________ 36,2 / 38,9 / +7,5%
4) Chris's 3D Benchmark 640x480 __ 11,4 / 11,5 / +0,9%
5) PC Player Benchmark ________ 12,8 / 14,5 / +13,3%
6) PC Player Benchmark 640x480 ___ 4,9 / 5,6 / +14,3%
c) Doom (Faster PCs) __________ 27,2 / 30,1 / +10,7%
d) Quake timedemo ___________ 9,2 / 10,1 / +6,8%

Repeated with Matrox Mystique 4MB:

Am486DX2-100SV8B @ 33MHz x3:
1) 3DBench 1.0c (Slower PCs) ______ 58,8 / 66,6 / +13,3%
2) 3DBench 1.0c (Faster PCs) ______ 57,2 / 62,8 / +9,8%
3) Chris's 3D Benchmark ________ 40,5 / 45,1 / +11,4%
4) Chris's 3D Benchmark 640x480 __ (does not run on Mystique out of the box)
5) PC Player Benchmark ________ 13,3 / 15,0 / +12,8%
6) PC Player Benchmark 640x480 ___ 6,4 / 7,2 / +12,5%
c) Doom (Faster PCs) __________ 33,3 / 38,0 / +14,1%
d) Quake timedemo ___________ 9,4 / 10,3 / +9,6%

Reply 24 of 62, by Paadam

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Excellent and super cool!!! Extremely nice effort and pure admiration to your skills!!
Now, how could I (we) purchase this kind of module from you? 😀

Many 3Dfx and Pentium III-S stuff.
My amibay FS thread: www.amibay.com/showthread.php?88030-Man ... -370-dual)

Reply 25 of 62, by ChrisK

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Thank you very much!
I didn't think it would work. But I'm quite happy with the result 😁

It would be good to know if there is anyone else interested in such a module because I will have to order all necessary parts which isn't very easy for me at the moment.
My favorite shops (and the only ones which have everything needed) have a minimum order amount of 50 EUR. Otherwise they charge high shipping costs of around 20 EUR.
And I have to find out if they sell to private customers...
So there should be at least two more people interested in this module to make the price reasonable.

Next question is what price would be ok for you (and others) at all? I guess it will be between 25-30 EUR excl. shipping.

Let me know what you think.

Reply 27 of 62, by ChrisK

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Alright!
There is another user in another thread here who said he'd be interested. I already posted there too but I don't know if/when he reads this and if he's still interested at all.
I would like to wait a few days and if he doesn't reply I will see what I can do to get a module for you.

I'll give notice here as soon as possible.

Reply 28 of 62, by ChrisK

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Does anyone know if there is some kind of header or input for a reset switch on the TC40 board?
Everytime the system hangs I have to power off, power on. So a reset switch would be very nice...
There is an unpopulated J9 header next to the IDE port on my board. But it's function is unknown to me.

Reply 29 of 62, by Paadam

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Never looked for it, maybe someone skilled could give some insight after some measurements and tracing where it goes?

Many 3Dfx and Pentium III-S stuff.
My amibay FS thread: www.amibay.com/showthread.php?88030-Man ... -370-dual)

Reply 31 of 62, by ChrisK

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Hi Paadam,

very big sorry for the delay! I have been quite busy in the last time.

I was able to prepare a cache module with some left over parts for you already some time ago. However, I'm still missing the SRAM chips. I ordered them from Asia but the order was cancelled some time later for unknown reason. I wanted to start a new order but then I've seen some instabilities of my system while benching with L2 cache enabled.
As it turned out it seems to be an issue with the Matrox Mystique 220 I used for benching. With enabled L2 cache some benches and also some games crashed when run at VGA resolution.
Retesting with a Riva TNT and an ATI 264VT2 (and also the onboard Cirrus Logic) did not show any instabilites so I guess it is related to the Mystique only in some way (with which I have also seen crashes in Chris's 3D Benchmark at 640x480 and without L2 cache before).

But back to the module: How are your soldering skills? If you like I could send you the module with all components excluding the SRAM chips. You would have to order and solder them on your own.
If you don't want/can do that I'll see if I can order the SRAM chips again in the next days. Unfortunately, no one else declared interest in such a module.

Let me know how we shall proceed.

Btw, I found the reset switch connection of the TC40 board and also was able to tune it to 40 MHz FSB. It now runs a Am586-dx5-133 @160MHz 😉

Reply 32 of 62, by Paadam

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Glad to hear from you! I can solder quite well, I do soldering as daily thing, including SMD parts, chips etc.

But of course I would prefer to have it readymade like intended from the inventor 😀

Many 3Dfx and Pentium III-S stuff.
My amibay FS thread: www.amibay.com/showthread.php?88030-Man ... -370-dual)

Reply 35 of 62, by peda126

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Hi ChrisK,

can you share how you managed to get a 40Mhz FSB to run the AM5x86 @ 160MHZ?

Nice job on reengineering the L2 cache module!! I would take one, but i have an original one that came in the machine.

Danke
Peter

Reply 36 of 62, by ChrisK

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Hi Paadam,

little update: no luck with chinese sellers so far. Got two more cancellations for my SRAM orders after one and a half week without shipment info.
But I got 8pcs new locally. So only two more left...
I will see if can order these via my company.

Another thing:
Did you ever try to put in a larger harddrive than 2 GB?
I tried to figure out the max capacity the BIOS can go with without any drive overlay thing.
With my BIOS version it seems to be 2 GB (CHS: 4095 / 16 / 63). One can enter the heads parameter up to 63, but with this some calculation thing brings it always back to max. 1 GB.

I found that Phoenix BIOS 4.03 and 4.04 are limited to 3.2GB hard drives due to a bug in the drive size calculation routines which cause a hang in the BIOS.
But as mentioned before my particular version seems to max out at 2 GB already.
I just wondered if there are other/newer BIOS versions with these bugs fixed (mine is 04/07/1995).

Last edited by ChrisK on 2021-06-17, 12:15. Edited 1 time in total.

Reply 37 of 62, by ChrisK

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Hi peda126,

for 40 MHz FSB you have to unsolder a resistor and add a 2pin jumper. Pls see the picture: resistor marked red (I just put it upwards), jumper connection points marked green.
This in combination with J23 set to 50/25 sets the clock gen to output 80 MHz, which is scaled down to 40 FSB (& PCI !!!) by the Intel chipset.
With this configuration the ISA slots get 13,3 MHz instead of 8,25 MHz. If this is a problem depends on the cards you use.

There is the possibility to lower the ISA clock to 10 MHz, but for this another resistor needs to be removed (R253, just up-left from the big yellow part in the picture) and a 3pin jumper to be added over R117 & R118 (mid-point is the common connection point of these two resistors. This basically disconnects CMDV# signal (one of two strapping signals setting the clock configuration) of the Intel ISA-bridge from J23 and allows setting it independently LOW/HIGH which in turn allows setting the SYSCLK (aka ISA-clk) divisor freely between 3 and 4.

This table shows the combinations my system was able to run with. J23a is the 2pin jumper from above.

J23 J23a SIDLE# CMDV# CPU PCI SYS/ISA
50/25 open 0 0 25 25 8,33
66/33 open 0 1 33 33 8,25
50/25 set 0 0 40 40 13,3
50/25 set 0 1 40 40 10

I also added the missing clock divisor settings intel set to reserved. With these and the input clock from the clock generator (50/66/80/100) all other clocks can be calculated.
Unfortunately only the two additional 40 MHz settings from my table proofed to be usable/stable. All others either don't POST or hang just after POST.
At least one setting seemed to be just fine (FSB 50 MHz, PCI 25 MHz, ISA 10 MHz) but didn't POST too.

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Reply 38 of 62, by Paadam

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I use 20GB HDD, without any overlay. BIOS sees it as 8 GB drive and since I wanted to clone original W3.11 installation I just partitioned it in DOS and made 2,1 GB FAT16 partition. No additional software used.

Nice information regarding 40MHz FSB. I have am486-DX4 120 CPU laying around (with 8kb WB cache), that would work nicely I guess.

EDIT: My board is Level 4 if it matters.

Many 3Dfx and Pentium III-S stuff.
My amibay FS thread: www.amibay.com/showthread.php?88030-Man ... -370-dual)

Reply 39 of 62, by ChrisK

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Oh, nice.
What date is your BIOS?
If it is newer than mine could you try to make a backup of it?

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