PROM Modification

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PROM Modification is required to enable telnet/ftp access to newer TiVos, including

  • Series 2 Stand Alone TiVo's with the following model numbers: TCD540040, TCD540140, TCD649080 (dual tuner)
  • Series 2 DirecTiVo RCA DVR R10
  • Series 2 Humax DRT800 and DRT2500 (DVD Recorder)
  • Series Toshiba RS-TX20 and RS-TX60 (DVD Recorder)
  • Series 3 (TCD628450) and TiVo HD Stand Alone

Unlike with earlier models, the PROM chip (similar to a computer BIOS) in these models can't be reprogrammed. The PROM chip provides restrictions that prevent the installation of third-party software. It must be replace with a PROM chip that can be reprogrammed to disable these access restrictions so that you can gain telnet/ftp access to your TiVo.


PROM (Programmable Read-Only Memory - Wikipedia PROM info) chips are a part of the main system board of every TiVo. The PROM software conducts a check of the Linux Kernel running on the TiVo. The kernel must be modified for third-party software to be installed. If the PROM detects an non-approved kernel running, it will not allow the TiVo to boot.

On older TiVos, the PROM chips would be reflashed by removing the hard drive from the TiVo, copying software on to it to run as soon as the system boots, and that software would re-flash the PROM so that restrictions were disabled and non-TiVo software could run on the TiVo.

New models of TiVos (listed above) have a different type of PROM chip that can not be re-programmed while installed in the TiVo. A change to the chip design make it physically impossible to do so. It is necessary to remove (unsolder) the PROM from the board, reprogram it, and then reinstall it. This will result in a PROM chip that does not contains the restrictions of the original code.

The most difficult part of this sequence is the fact that PROM chips are soldered to the TiVo main system board. It is necessary to remove these chips for them to be reprogrammed. The solder joints are very small and a skilled person with specialized soldering equipment is required to remove the chips. Some people choose to replace the stock PROM chips are replaced with a socket and socket-compatible PROM. This allows the replacement chip to be easily pulled from the board, re-flashed, and reinstalled with no soldering if it every needs to be re-flashed (which is unlikely).

How to Reflash a TiVo PROM

Replacement PROM chips Model Numbers

The OEM PROM chip in the TiVo is an SST37 chip, and requires 3V to read, but 12V to erase. This means that most programmers will not be able to program it, and that the TiVo will be unable to reflash the chip in-place. A special programming device is required to reflash this chip. If you have this programmer, you can reflash and reinstall the stock chip.

The SST39 is identical in every way to the SST37 but can be erased and programmed with 3V. Many people prefer this one if they are trying to use various home brew methods of flashing the chip.

One potential (but highly unlikely) issue with the SST37 is that is opens up the possibility of TiVo providing a software update that re-writes the chip. It hasn't happened yet, and it's unlikely that TiVo would ever do so, but it's still possible and it would be possible to re-flash it again yourself but you would just have to take the time to do it. Realistically, once the chip is flashed it never needs to be reflashed. Otherwise, TiVo would have used a SST39 instead of SST37 at the factory. As long as you have a 12V programmer, the 12V chip.

Sources of Replacement PROM Chips

  • The SST37 (exact part no. is SST37VF010-70-3C-NH) is manufacturer by SST (Silicon Storage Technology, Inc) and can be bought in these distribuitors .
    • The alternative for this chip is the SST39. These are the part numbers: SST39LF010-45-4C-NH, SST39LF010-45-4C-NHE, SST39VF010-70-4C-NH, SST39VF010-70-4C-NHE, SST39VF010-70-4I-NH, SST39VF010-70-4I-NHE

PROM Programmers for your PC

Sources of PROM images to flash to the PROM chip

Known PROM Replacement Services

[1] - This post on the DealDatabase Forum details PROM services offered by Omikron. There are other pages that link to his services such as the website, but those pages are outdated and no longer show correct information.

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