TMC PET48PN EISA+VL Motherboard 50 Mhz bus testing

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TMC PET48PN EISA+VL Motherboard 50 Mhz bus testing

Postby Madowax » 2018-11-29 @ 16:39

I have recently acquired this board and took some pictures of the test bench I have arranged with it, I know there are some supporters and experts of 486 EISA Systems on this forum, so I hope to receive suggestions and comments about it.

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It's a TMC PET48PN Rev.1.0, an EISA+VLB board based on Opti 82C681 Chipset.
The board components datecode places it mid-1992, it has 8x 30 pins SIMM slots and 2x 72 pins SIMM slots, it only accepts parity simms from what I have tested, it doesn't post with no parity modules. There are 8x 28 pins 300 mils sockets + 4x 32 pins 400 mils sockets for L2 cache and 1x 28 pins 300mils socket + 2x 22 pins 300mils sockets for tag ram chips, the board supports a total of 128 MB RAM and a maximum of 256KB double banked or 512 KB single banked L2 cache. Due to the particular tag chips configuration it can cache all the 128 MB RAM and the cacheable memory size it's configurable in the BIOS: the settings are 4 MB through 64 MB in 4 MB increments and then you can select 128 MB. The Opti 82c681 datasheet states that the L2 cache is always in WB mode, there are no options in bios to change this.

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The BIOS is by AMI and it's a classic Hi-Flex with 1992 core, it got memory timing settings hidden, but they are still configurable with Amisetup 2.99. The board uses a RTC chip to save standard cmos and eisa cmos data, it's a DS1387, pretty much equal to DS1287 but with more NVRAM (4KB in total), when I received the board the internal battery was depleted so I hacked it with a CR2032 battery holder.
The board was certified by the manufacturer as 50Mhz bus capable and tested, the value 50Mhz has been imprinted on the Opti 82C682 IC, on a sticker in a corner of the board and in the bios string ID, as other EISA board it also got a unreported 66 Mhz bus jumper setting. (Jumper settings: https://stason.org/TULARC/pc/motherboards/T/TMC-RESEARCH-CORPORATION-486-PET48PN.html)
I decided to use with it the following peripherals:

2x 16MB Siemens Parity FPM 72 pins SIMMs
Miro Crystal 12sd VL with 2 MB video dram (s3 trio32 vlb)
Adaptec AHA-2740W
Acard 7726 with CF-IDE adapter
PNY Quickchip133 (AM5x86-P75 with VRM) @ 3x50Mhz WT
Audio board still to decide
Network adapter COMPAQ Netflex 3E, I still have to acquire one of those. ;)

I used the following ECU to configure the EISA Scsi adapter in EISA NVRAM:ftp://ftp.necam.com/swan-zds-ftp/ecu/tmc/tmcecu27.zip
The Miro Trio32 works with 50Mhz bus at 0WS jumper settings on the mainboard.




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Some benchmarks results:

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Doom FPS: 50.67
1474 realtics/2134 gametics (formula 35 x gametics/realtics)
Quake timedemo 320x200:
15.0 FPS
3DBench 1.0c:
84.2
PcPlayer 320x200:
20.7
PcPlayer 640x480:
7.6
Chris 3d Benchmark:
61.6

Considering that the board is from 1992 and the VL VGA is only 32bit, these scores are not that bad imho. More to follow...
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Re: TMC PET48PN EISA+VL Motherboard 50 Mhz bus testing

Postby Anonymous Coward » 2018-12-01 @ 12:02

Cool, I didn't know that these were officially rated for 50MHz. The memory performance numebrs look alright.
I used to have one of these, but I wanted more support for cache and RAM so I sold it and got some SiS boards.
Another thing that kind of bothered me is that these TMC boards strangely lack a ZIF socket.
Will the highways on the internets become more few?
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium
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Re: TMC PET48PN EISA+VL Motherboard 50 Mhz bus testing

Postby Madowax » 2018-12-01 @ 14:04

Anonymous Coward wrote:Cool, I didn't know that these were officially rated for 50MHz. The memory performance numebrs look alright.
I used to have one of these, but I wanted more support for cache and RAM so I sold it and got some SiS boards.
Another thing that kind of bothered me is that these TMC boards strangely lack a ZIF socket.


Indeed the max L2 cache for Opti 82c681 is 512KB single banked so you loose the memory interleaving, memory performances are also lower than SIS EISA chipset, however it's also true that the bios is a Hi-flex 6/6/1992 core, I'm quite sure that with an updated bios from 1994 core the performances would be much better. AMI Baby EISA and ACER POWER 486e mobo used the same chipset, might try one of those bios if I will manage to find them. I also tested the HDD speed of the aha-2740w and it tops at 16MB/s using wide channel. Overall the system is very stable and it doesn't seem slower using it than a late 486 PCI system 4/5 years younger.
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Re: TMC PET48PN EISA+VL Motherboard 50 Mhz bus testing

Postby Anonymous Coward » 2018-12-01 @ 14:49

I think you will be sorely disappointed with any BIOS from an Acer system. I have an Acerpower EISA active backplane board (J3) with a dual P60 card (it can also take a 486 card). The BIOS is from 1993 or 1994, but it's some proprietary acer crap. It's not an OEM job from phoenix or award. The options are very limited, and the performance stinks. I think the AMI BIOS is pretty decent. I suspect the AMI Baby EISA board uses a BIOS with the sa me same core you already have. I doubt they made a winbios for that product. Generally for EISA 486 boards, 1993 is as good as you can get.

Did you try overclocking your EISA bus to 10MHz to try to squeeze out a little more bandwidth. If you got 16MB/sec out of your wide SCSI controller, you're doing pretty well. It tops out at 20MB/sec.

Also, I agree with your assessment that these EISA 486s (especially when using overdrive chips) feel more like later PCI systems.

Can you benchmark your Trio32 using DOOM Timedemo3 (Fullscreen, no sound) and 3Dbench2? I heard a rumour these are a hair faster than Trio64 in DOS and I want to know if it's true.
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Re: TMC PET48PN EISA+VL Motherboard 50 Mhz bus testing

Postby Madowax » 2018-12-01 @ 16:29

Anonymous Coward wrote:I think you will be sorely disappointed with any BIOS from an Acer system. I have an Acerpower EISA active backplane board (J3) with a dual P60 card (it can also take a 486 card). The BIOS is from 1993 or 1994, but it's some proprietary acer crap. It's not an OEM job from phoenix or award. The options are very limited, and the performance stinks. I think the AMI BIOS is pretty decent. I suspect the AMI Baby EISA board uses a BIOS with the sa me same core you already have. I doubt they made a winbios for that product. Generally for EISA 486 boards, 1993 is as good as you can get.

Did you try overclocking your EISA bus to 10MHz to try to squeeze out a little more bandwidth. If you got 16MB/sec out of your wide SCSI controller, you're doing pretty well. It tops out at 20MB/sec.

Also, I agree with your assessment that these EISA 486s (especially when using overdrive chips) feel more like later PCI systems.

Can you benchmark your Trio32 using DOOM Timedemo3 (Fullscreen, no sound) and 3Dbench2? I heard a rumour these are a hair faster than Trio64 in DOS and I want to know if it's true.


Yep probably you are right and Baby EISA uses the same core, I have read the Ami manual and the bios options described are exactly the same as mine. Even the shortcut keys to enable disable l1 and L2 caches works with the TMC board.
Using amisetup 2.99 I can fine tune ram and cache timings, the board at 50 Mhz automatically reverts to 3-2-2-2, 1 WS for Cache writes and 1 WS for DRam, I can maintain stability in Dos/Win 3.11 bringing it at 3-1-1-1 and 0 WS for DRam, the results you asked are the one reported in the first post:
3DBench1.0c (3DBench2): 84.2
Doom Timedemo3 fullscreen/nosound: 1474/2134 which should translate to 50.6 fps.

Edit:
Screenshot of a last minute cachechk (sorry for the flash)
Image
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Re: TMC PET48PN EISA+VL Motherboard 50 Mhz bus testing

Postby Anonymous Coward » 2018-12-02 @ 04:59

Next time I have a moment, I'll compare your results to my system with a Trio64.

If you ever get a chance, see if you can get a Cyrix 5x86 working in your VL/EISA board. I have issues getting them working.For the 2X/3X type chips I can only get those working if I set the multiplier to the "2.5X" setting, which actually connects to "BREQ". So far the only 3X/4X chip I have tried does not work at all! It's a 100/4X. I also have an Evergreen 133MHz Cyrix 5x86 kit that I haven't had a chance to play with yet. It has an interesting interposer that may fix some incompatibilities. It's supposed to be specifically for certain types of OEM systems.

I've been having a hard time deciding on which CPU to go with.
In the end it's either going to be an AMD 5x86 at 150 or 160, or a Cyrix 5x86 at 120 or 133.
I've tried replacing the oscillators in my boards to squeeze out extra performance from both of these chips, but so far I've failed on all counts.
I tried:
am5x86 at 180MHz using a 60MHz clock
am5x86 at 170MHz using a 42.5MHz clock
cx5x86 at 127.5MHz using a 42.5MHz clock.
Even varying the voltage did not help. I think I could boot into NT4 with the AMD, but it would eventually lock up. I have good cooling too. It was a B1 stepping made in 2001.
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Re: TMC PET48PN EISA+VL Motherboard 50 Mhz bus testing

Postby Madowax » 2018-12-02 @ 08:28

I have 2x IBM 5x86-100 but no interposer with VRM for them, I have tested on this board an Intel 486dx4-100 overdrive and of course it works, but @33mhz bus it doesn't shine like the Am5x86-P75 @50mhz, I should try it at 40x3. I will post some results in the next hours.
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