Classic Technology Speed 286 add on accelerator for 8088s. Bad Ram.

[dabone]

I've got a Classic Technology Speed 286 in a compaq portable that keeps giving parity error stops when it's enabled. (Can't get things to boot to test, and it's got it's own bios, so I don't think I can throw a diag rom in there.)

The board had 4 256mb sipps soldered on the board that I've removed.

I'm coming up blank with a datasheet for the chips on the original sipps. They are Hitachi 50256CP15M.

The new (to me sipps) I got in have 2 MT4C256DJ-7 s and a AAA2800J-06 chips, so they have parity, but I don't know if fast page ram is compatible.

I also have the option of putting simm sockets on the board instead of the soldered in sipps, but that requires moving some components to the back of the board, and doesn't keep the original look. (r12 is on the back currently while I was testing the fit.)

 

[Plasma]

If it was my board I would solder in SIPP sockets. Then you can easily swap out SIPPs, or even SIMMs (using the socket in a socket trick).

 

[modem7]

I'm coming up blank with a datasheet for the chips on the original sipps. They are Hitachi 50256CP15M.

See Hitachi HM50256 at [here].

 

[modem7]

I'm coming up blank with a datasheet for the chips on the original sipps. They are Hitachi 50256CP15M.

See Hitachi HM50256 at [here].

Additional information:

The CMOS version of the chip is the HM51256. ('1' instead of '0'.)
The HM51256 data sheet at [here] shows that the 'CP' portion of HM51256CP-15 indicates a PLCC package.
Your HM50256CP-15 will be the NMOS version of the HM51256CP-15.

 

[dabone]

Ok, can Fast Page ram be subbed for page mode ram?

 

[Eudimorphodon]

So, my completely not-authoritative-in-the-slightest take after reading a functional description of the two is… I think so? What I took away from it was that FPM is basically the same as PM except for some internal differences in how it handles the column latches that allow it to cycle faster. From what I can see comparing the actual cycle diagrams between a 256k FPM chip and an ancient 16k PM one externally the same cycling pattern applies.

This is assuming the original SIPPs are in fact *not* actually FPM? The datasheet calls them “High Speed Page Mode”…

 

[dabone]

Fast Page rams seem to run as well as the originals. And I get get through a memtest in checkit now, but the system still isn't that stable.

I guess I need to put the original video adapter in. I scored a nos Compaq ega adapter that had the internal monitor connector and I noticed the system running less stable after I installed it, but I thought it might be the accelerator ram.

Has anyone ever seen the manual for that Accelerator? I'd love to see that, there's headers on the back for what I assume is a memory upgrade board, and what it used for upper memory access, himem.sys gives the can't control the A20 line error.