Recent content by prime

Hi all, I've been designing a 16 bit XMS board for use on AT class motherboards that have limited onboard expansion. For example I have a Commodore PC-40-III that can only have 1MB onboard. The board currently consists of between 2 and 8 AS6C4008-55PCN 512K x 8 bit SRAMs (one each for the high...

Hi all, Anyone know of a convenient way of adding a reset button to the 8MHz version of the 5170 motherboard? Cheers. Phill.

Hi all, Does anyone have the schematic for the Holmes Sprinter III, the documentation refers to a schematic but it's not included in the PDF file. Cheers. Phill.

Hi all, I have an IBM branded TM-100-2A 40 track DS drive that I'd like to repair. Last time it was used it suffered a mildly catostrophic failure (c36 a 475, which if I'm reading correctly is 4.75µf, tant capacitor went pop and caught fire!). I can source and replace this cap easily enough but...

Hi all, I have a model 3 with a FreHD, which can boot LDOS 5.3.1 or Newdos. I can format a floppy disk from both but is there an easy way of transfering the system to them so that they are bootable on a mchine without a FreHD (or with the HD disconnected). Cheers. Phill.

Hi all, Does anyone know if there is an archive of the source / a dissasembily of either TRSDOS or LSDOS for the TRS80 Model 3 available anywhere? I've searched and come up with nothing. Cheers. Phill.

Hi all, I have a working TRS80 model 3 motherboard, but that's all I have :( I'm using a PS2->Crosspoint switch to implement the keyboard, and have a circuit using a 74LS02 and some discretes to combine the syncs and video into a composite sync like signal. However when I feed this into one...

Hi all, I keep seeiing refferences to the later versions of the Model 4 using a 177x based floppy controller (e.g. Wikipedia), but cannot find a schematic for this. Does anyone know if it is available and if so where? Cheers. Phill.

Hi all, I have one of the Universal PET boards with the 6845 video controller, that I'd like to power up. I have tested the board in my PET 3008 and it seems to work without problems. However I only have one PET case :( So does anyone have the specs of the mains transformer please, or advice...

Hi all, Following on from my post about imaging.... Is there documented anywhere an explanation of the translation scheme used by the XTIDE universal bios ? Also is there a way of enquiring of the drive e.g. via an INT call to find out what scheme is currently in use? Cheers. Phill.

Hi all, So here's the setup I have a 5150 PC with a WD MFM controller in it, attached to this is a 20MB hard disk. This all works fine but I wanted to take a dump of the hard disk for backup / emulation purposes. The machine is running PC-DOS 4. So I installed an XT CF lite rev 2, jumpered so...

Hi all, Is there a program that will test memory above 640K on a PC / XT class machine. Specifically I want to test memory in defined UMB areas. e.g. the 128K D000-EFFF Cheers. Phill.

Hi all, I'm trying to update the firmware on my Lo-tech CF-LITE v2 to the lates XTIDE firmware. I've tried using both the IDE-XT and IDE-XTL, but obviously edited the settings to be XT-CF v2/v3/Lite in PIO mode base address 0x300 (which my card is jumpered for). Saved the bios, combined it...

Hi all, I finally think I've got to the bottom of the problems I was having with interfacing a DS12887 with the PC-RETRO board. The PC-RETRO is a chip for chip copy of the 64K-256K 5150 board and so therefore has all it's problems / limitations, namely incomplete address decoding of the I/O...

Hi all, Am I correct in assuming that only *ONE* of the the memory or I/O write strobes may be active at one time e.g. nMEMR, nMEMW, nIOR, nIOW ? The reason I ask is because I have a RAM / Clock card (I have been developing on and off for a couple of years), this has an 74ALS245 buffer between...