Mike1978 wrote on 2024-09-18, 21:49:Interested in this process any chance you can share some pics. I have 2 model 30 286 machines and one of the 12 slot memory card […]
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pipmastah wrote on 2023-04-01, 22:58:
Necromancing this old topic, which I find very interesting as a PS/2 / IBM afficianado 😉
My Model 30 286 was very unstable as well when clocked at 12MHz and it took me some time to figure this out but mine runs super stable now at 12MHz with 80ns memory after I completely disabled the parity controller. This is easily done by cutting the 2 "PAREN" traces at the memory controller (VL82C102) and the VL82C104 data buffer IC. Both chips have internal pull down resistors so cutting these traces will pull the PAREN (PARity ENable) signal to ground which will disable parity checks. The parity logic on these boards is slow as dog sh!t and unable to keep up with that blazing 12MHz clock speed (probably caused by a 7400 series latch that cannot keep up) which results in false parity errors that occur randomly so I decided to delete it on my system 😉
Next step is enabling "fast mode" to get to 0 wait state read operations and then the planar will run at its fullest potential (VLSI states that 0 wait state reads is supported when 80ns memory is used). This may need some extra logic added to the board but I'll figure it out as this is one of the few IBM machines that have proper technical documentation for the (VLSI) chipset. After that I will put in a 40MHz 286 to 486 upgrade, a fast ISA videocard and maybe some extra memory. It's a bit of a challenge to build one of the fastest Model 30s that can "easily" run Doom and Windows 95 but I think I'm making some progress 😉 Getting the board itself and memory access times as fast as possible really is a must have for CPU upgrades like these!
Interested in this process any chance you can share some pics. I have 2 model 30 286 machines and one of the 12 slot memory cards mentioned in the earlier posts so I would love to get that filled with ram chips
I don’t yet understand how to do the mods to the ram but if anyone can give me steer I’d be happy to give it a go. Frustratingly one of the caps blew on the memory card the first time I powered it up so will have to replace one of the tantalum’s.
Would like to also get mine sped up. I have a few potential cpu upgrades also to try.
I do like to try and push these old girls.
Also does anyone have a manual for the ram card or details about drivers / config I couldn’t locate anything yet online though it led me here.
Card Id is marked as DET 55X3544
Mike
Hi dude,
So we meet again; It's a small world indeed!
Sorry it took me over a year to respond. This is the first time I revisit this topic in years because I continued my own turbo charged Model 30 286 project recently.
I modded the four 9 chip 80ns planar SIMMs using this guide: http://john.ccac.rwth-aachen.de:8000/misc/ps2cache/
Then I simply cut the PAREN signal on two places, taking out the parity controller. After that I swapped the 20MHz CPU crystal with a 32MHz variant and swapped the CPU with a 16MHz AMD 286, put in a Tseng ET4000 as the OG 8-bit on planar VGA is a dog in terms of performance and everything just worked like a charm.
Then I went even further and threw in a 33MHz Kingstong SX/Now! which I got from a friend. This worked rather nicely but somehow my 33Mhz Kingston SX/Now! upgrade just blew up! 🙁
So I decided to throw in a 50 MHz SLC/Now! card I had in my stash. It's a card that was meant for the Model 60 so the BIOS of my 30 really didn't like the Kingston driver they supplied with it.
Also my machine refused to run at 16MHz FSB and with its parity controller disabled so I reverted back to 10MHz and parity to get the SLC going (it's a nice 50MHz SLC2 upgrade). I got it going indeed and without the Kingston driver I was fully able to switch to 386 protected mode but it obviously slow as a snail because it ran at 10MHz and without any cache..
Somehow my Model 30 really does not like the driver Kingston supplied. I guess it does some weird A20 line voodoo that only a Model 60 understands or some model specific BIOS calls so I ditched that as it would even crash my machine when the driver was loaded with the L1 cache and clock doubling disabled! So I had to get creative and used KTChip34 to control the SLC's registers directly which seemed to work. At least I could see them change and when I enabled the clock doubling register the machine would display as a 50MHz machine in Checkit for instance. Only its performance was still that of a 10MHz 286! Either the ASIC on the Kingston module must have some internal wait state logic as a fail safe that needs to be deactivated or the registers on the CPU itself are somehow "protected". I also saw a few posts that mentioned this safety feature but no one seemd to know how to circumvent it.
So I was close to giving up but then I remembered that Evergeen also made some very upgrades like these. I own one of them but mine doesn't feature an IBM SCL. It has a TI 486SXLC-40 but I remembered they also had a version with this exact nice IBM 486SLC2-50 CPU on it so I used Evergreen's Revto486 driver, "revto486.sys" and lo and behold: It worked! But it only works when I make sure the CPU is in 386 protected mode before loading the Evergreen driver and DOS is running in virtual x86 mode. I still have some performance tweaks that I need to do but it runs fastDooM rather nicely. Really a lot faster than the SX-33 which is of course no surprise 😀
Cheers from the Netherlands!
