First post, by Madowax
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.
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.
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/motherboar ... T48PN.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)
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.
Some benchmarks results:
Doom FPS: 50.67
1474 realtics/2134 gametics (formula 35 x gametics/realtics)
Quake timedemo 320x200:
Chris 3d Benchmark:
Considering that the board is from 1992 and the VL VGA is only 32bit, these scores are not that bad imho. More to follow...