My aim is to run the Harris CPU at 10 MHz, but am unsure if there is some detail to keep my eyes on, e.g. supply voltage(s) or other things.
This is for an IBM PS/2 model 30-286.
I imagine it should be straight forward as long as the model 30 motherboard takes a 286 with 68-pin PLCC packaging.
It should just be a matter of replacing the chip, and if the original CPU isn't an LCC version it should be quite easy.
T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜
Tiido wrote on 2024-04-12, 18:10:It should just be a matter of replacing the chip, and if the original CPU isn't an LCC version it should be quite easy.
Thank you. The CPU is housed in a PLCC package, so it isn't the LCC version 286. So I should be good to go.
Is there any PLCC Harris variant of the 286 that would not be suitable? Asking because I have a few 25 MHz ones, aslo. I have no suitable motherboard for 25 MHz 286 CPUs.
douglar wrote on 2024-04-12, 18:05:I imagine it should be straight forward as long as the model 30 motherboard takes a 286 with 68-pin PLCC packaging.
Thank you.
You'd have to replace some crystal too. Also, this system was designed with 10MHz in mind, so all components are rated 10MHz. Overclocking to 12MHz (20%) Will put more stress on the other components as well. This may ruin them hotter than intended and probably cause instability.
The 8530-286 was designed as budget solution after all (well, for IBM standards ofcourse)
Stuck at 10MHz...
Right, just to be clear, if you put a CPU rated for up to 25MHz in a motherboard running at 10 MHz, the CPU will run at 10 MHz. But in the 286 world, there were never any voltage or cache changes between the different versions, so thats all pretty simple. But changing the clock speed of a 286 motherboard is a more difficult proposition that likely will require some soldering and some luck. Motherboards with selectable speeds were extremely rare in the 286 days and the chances of putting a faster crystal on a 286 motherboard and having it work are unclear, especially with a PS2 model 30.
waterbeesje wrote on 2024-04-13, 09:09:You'd have to replace some crystal too.
No, OP clearly says he wants to run the CPU at 10MHz.
Which makes me curious to learn why, is it to replace a confirmed dead CPU and the 12MHz one just happened to be available/cheaper?
Most of these machines have a NMOS 286 which is like a little furnace. If that 12MHz Harris part is a CMOS one, it'll run waaaay cooler. This is one thing I will do in my Toshiba T3200 once I replace the LCC with PLCC socket in it, I may not get more speed but I definitely get less heat/power use.
T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜
Yes the Harris 80C286 are cmos and draw about 40% of the n-mos AMD's. Swapped a AMD 16Mhz 3w for a 16Mhz Harris 1.3w because of the heat....
Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun
douglar wrote on 2024-04-13, 10:38:and the chances of putting a faster crystal on a 286 motherboard and having it work are unclear, especially with a PS2 model 30.
Yah the 386 models have a "timing circuit sanity check" in POST which fails anything more than 5-10% different that it is expecting, according to IBM to assure correct function and prevent damage or data loss, oh dearie dearie, such a shame it stops you from being able to upgrade the crystal and CPU, but it wasn't intended to force you to buy the next model up for an extra thousand bucks, swear on our mother's graves.
So you may encounter similar obstacles "for your own good" in 286 models.
Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.
You guys miss that HMOS also existed and that some 80286 had used it, too.
HMOS was derived from NMOS, but more efficient than ordinary NMOS.
"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel
//My video channel//
HMOS is intel's trademark for their own depletion-load NMOS process, everyone else had something like it too. All Intel's 286 CPUs were in one of the HMOS processes and run like little furnaces 🤣
T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜
waterbeesje wrote on 2024-04-13, 09:09:You'd have to replace some crystal too. Also, this system was designed with 10MHz in mind, so all components are rated 10MHz. Overclocking to 12MHz (20%) Will put more stress on the other components as well. This may ruin them hotter than intended and probably cause instability.
The 8530-286 was designed as budget solution after all (well, for IBM standards ofcourse)
I wrote that my intent is to run the CPU at 10 MHz right there, in my extremely short opening post 😀 it should have been hard to miss.
konc wrote on 2024-04-13, 11:33:waterbeesje wrote on 2024-04-13, 09:09:You'd have to replace some crystal too.
No, OP clearly says he wants to run the CPU at 10MHz.
Which makes me curious to learn why, is it to replace a confirmed dead CPU and the 12MHz one just happened to be available/cheaper?
I could not find Intel 286 at 10 MHz for a reasonable price, whereas the Harris 286 were cheap.
